Update javaxval/src/test/java/org/baeldung/javaxval/messageinterpolator/ParameterMessageInterpolaterIntegrationTest.java

update to use the givenX_whenY_thenZ naming convention for tests

Co-Authored-By: KevinGilmore <kpg102@gmail.com>

kotlin-libraries/.gitignore

@@ -0,0 +1,14 @@
+/bin/
+
+#ignore gradle
+.gradle/
+
+
+#ignore build and generated files
+build/
+node/
+out/
+
+#ignore installed node modules and package lock file
+node_modules/
+package-lock.json

kotlin-libraries/README.md

@@ -0,0 +1,17 @@
+## Kotlin Libraries
+
+This module contains articles about Kotlin Libraries.
+
+### Relevant articles:
+
+- [Kotlin with Mockito](https://www.baeldung.com/kotlin-mockito)
+- [HTTP Requests with Kotlin and khttp](https://www.baeldung.com/kotlin-khttp)
+- [Kotlin Dependency Injection with Kodein](https://www.baeldung.com/kotlin-kodein-dependency-injection)
+- [Writing Specifications with Kotlin and Spek](https://www.baeldung.com/kotlin-spek)
+- [Processing JSON with Kotlin and Klaxson](https://www.baeldung.com/kotlin-json-klaxson)
+- [Guide to the Kotlin Exposed Framework](https://www.baeldung.com/kotlin-exposed-persistence)
+- [Working with Dates in Kotlin](https://www.baeldung.com/kotlin-dates)
+- [Introduction to Arrow in Kotlin](https://www.baeldung.com/kotlin-arrow)
+- [Kotlin with Ktor](https://www.baeldung.com/kotlin-ktor)
+- [REST API With Kotlin and Kovert](https://www.baeldung.com/kotlin-kovert)
+- More articles: [[next -->]](/kotlin-libraries-2)

kotlin-libraries/build.gradle

@@ -0,0 +1,62 @@
+
+
+group 'com.baeldung.ktor'
+version '1.0-SNAPSHOT'
+
+
+buildscript {
+    ext.kotlin_version = '1.2.41'
+    ext.ktor_version = '0.9.2'
+    ext.khttp_version = '0.1.0'
+
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: 'java'
+apply plugin: 'kotlin'
+apply plugin: 'application'
+
+mainClassName = 'APIServer.kt'
+
+sourceCompatibility = 1.8
+compileKotlin { kotlinOptions.jvmTarget = "1.8" }
+compileTestKotlin { kotlinOptions.jvmTarget = "1.8" }
+
+kotlin { experimental { coroutines "enable" } }
+
+repositories {
+    mavenCentral()
+    jcenter()
+    maven { url "https://dl.bintray.com/kotlin/ktor" }
+}
+sourceSets {
+    main{
+        kotlin{
+            srcDirs 'com/baeldung/ktor'
+        }
+    }
+
+}
+
+dependencies {
+    compile "io.ktor:ktor-server-netty:$ktor_version"
+    compile "ch.qos.logback:logback-classic:1.2.1"
+    compile "io.ktor:ktor-gson:$ktor_version"
+    compile "khttp:khttp:$khttp_version"
+    testCompile group: 'junit', name: 'junit', version: '4.12'
+    testCompile group: 'org.jetbrains.spek', name: 'spek-api', version: '1.1.5'
+    testCompile group: 'org.jetbrains.spek', name: 'spek-subject-extension', version: '1.1.5'
+    testCompile group: 'org.jetbrains.spek', name: 'spek-junit-platform-engine', version: '1.1.5'
+    implementation 'com.beust:klaxon:3.0.1'
+}
+
+task runServer(type: JavaExec) {
+    main = 'APIServer'
+   classpath = sourceSets.main.runtimeClasspath
+}

kotlin-libraries/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-bin.zip

kotlin-libraries/gradlew

@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

kotlin-libraries/gradlew.bat

@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

kotlin-libraries/pom.xml

@@ -0,0 +1,177 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>kotlin-libraries</artifactId>
+    <name>kotlin-libraries</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-kotlin</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../parent-kotlin</relativePath>
+    </parent>
+
+    <repositories>
+        <repository>
+            <id>exposed</id>
+            <name>exposed</name>
+            <url>https://dl.bintray.com/kotlin/exposed</url>
+        </repository>
+        <repository>
+            <snapshots>
+                <enabled>false</enabled>
+            </snapshots>
+            <id>kotlinx</id>
+            <name>bintray</name>
+            <url>https://dl.bintray.com/kotlin/kotlinx</url>
+        </repository>
+    </repositories>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.jetbrains.spek</groupId>
+            <artifactId>spek-api</artifactId>
+            <version>1.1.5</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.spek</groupId>
+            <artifactId>spek-subject-extension</artifactId>
+            <version>1.1.5</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.spek</groupId>
+            <artifactId>spek-junit-platform-engine</artifactId>
+            <version>1.1.5</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>khttp</groupId>
+            <artifactId>khttp</artifactId>
+            <version>${khttp.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.nhaarman</groupId>
+            <artifactId>mockito-kotlin</artifactId>
+            <version>${mockito-kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.github.salomonbrys.kodein</groupId>
+            <artifactId>kodein</artifactId>
+            <version>${kodein.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.beust</groupId>
+            <artifactId>klaxon</artifactId>
+            <version>${klaxon.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.exposed</groupId>
+            <artifactId>exposed</artifactId>
+            <version>${exposed.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/io.arrow-kt/arrow-core -->
+        <dependency>
+            <groupId>io.arrow-kt</groupId>
+            <artifactId>arrow-core</artifactId>
+            <version>${arrow-core.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>uy.kohesive.kovert</groupId>
+            <artifactId>kovert-vertx</artifactId>
+            <version>[1.5.0,1.6.0)</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>nl.komponents.kovenant</groupId>
+                    <artifactId>kovenant</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>nl.komponents.kovenant</groupId>
+            <artifactId>kovenant</artifactId>
+            <version>${kovenant.version}</version>
+            <type>pom</type>
+        </dependency>
+
+        <!-- https://mvnrepository.com/artifact/junit/junit -->
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>compile</scope>
+        </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy-agent</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>compile</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.objenesis</groupId>
+            <artifactId>objenesis</artifactId>
+            <version>${objenesis.version}</version>
+            <scope>compile</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>io.reactivex.rxjava2</groupId>
+            <artifactId>rxkotlin</artifactId>
+            <version>${rxkotlin.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <junit.version>4.12</junit.version>
+        <mockito-kotlin.version>1.5.0</mockito-kotlin.version>
+        <kodein.version>4.1.0</kodein.version>
+        <klaxon.version>3.0.4</klaxon.version>
+        <khttp.version>0.1.0</khttp.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
+        <junit.platform.version>1.1.1</junit.platform.version>
+        <junit.vintage.version>5.2.0</junit.vintage.version>
+        <assertj.version>3.10.0</assertj.version>
+        <exposed.version>0.10.4</exposed.version>
+        <kovenant.version>3.3.0</kovenant.version>
+        <byte-buddy.version>1.8.13</byte-buddy.version>
+        <objenesis.version>2.6</objenesis.version>
+        <rxkotlin.version>2.3.0</rxkotlin.version>
+        <arrow-core.version>0.7.3</arrow-core.version>
+    </properties>
+
+</project>

kotlin-libraries/resources/logback.xml

@@ -0,0 +1,11 @@
+<configuration>
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%d{YYYY-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="INFO">
+    <appender-ref ref="STDOUT"/>
+  </root>
+</configuration>

kotlin-libraries/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = 'KtorWithKotlin'
+

kotlin-libraries/src/main/kotlin/com/baeldung/klaxon/CustomProduct.kt

@@ -0,0 +1,9 @@
+package com.baeldung.klaxon
+
+import com.beust.klaxon.Json
+
+class CustomProduct(
+        @Json(name = "productName")
+        val name: String,
+        @Json(ignored = true)
+        val id: Int)

kotlin-libraries/src/main/kotlin/com/baeldung/klaxon/Product.kt

@@ -0,0 +1,3 @@
+package com.baeldung.klaxon
+
+class Product(val name: String)

kotlin-libraries/src/main/kotlin/com/baeldung/klaxon/ProductData.kt

@@ -0,0 +1,3 @@
+package com.baeldung.klaxon
+
+data class ProductData(val name: String, val capacityInGb: Int)

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEither.kt

@@ -0,0 +1,54 @@
+package com.baeldung.kotlin.arrow
+
+import arrow.core.Either
+import arrow.core.filterOrElse
+import kotlin.math.sqrt
+
+class FunctionalErrorHandlingWithEither {
+
+    sealed class ComputeProblem {
+        object OddNumber : ComputeProblem()
+        object NotANumber : ComputeProblem()
+    }
+
+    fun parseInput(s : String) : Either<ComputeProblem, Int> = Either.cond(s.toIntOrNull() != null, {-> s.toInt()}, {->ComputeProblem.NotANumber} )
+
+    fun isEven(x : Int) : Boolean = x % 2 == 0
+
+    fun biggestDivisor(x: Int) : Int = biggestDivisor(x, 2)
+
+    fun biggestDivisor(x : Int, y : Int) : Int {
+        if(x == y){
+            return 1;
+        }
+        if(x % y == 0){
+            return x / y;
+        }
+        return biggestDivisor(x, y+1)
+    }
+
+    fun isSquareNumber(x : Int) : Boolean {
+        val sqrt: Double = sqrt(x.toDouble())
+        return sqrt % 1.0 == 0.0
+    }
+
+    fun computeWithEither(input : String) : Either<ComputeProblem, Boolean> {
+        return parseInput(input)
+                .filterOrElse(::isEven) {->ComputeProblem.OddNumber}
+                .map (::biggestDivisor)
+                .map (::isSquareNumber)
+    }
+
+    fun computeWithEitherClient(input : String) {
+        val computeWithEither = computeWithEither(input)
+
+        when(computeWithEither){
+            is Either.Right -> "The greatest divisor is square number: ${computeWithEither.b}"
+            is Either.Left -> when(computeWithEither.a){
+                is ComputeProblem.NotANumber -> "Wrong input! Not a number!"
+                is ComputeProblem.OddNumber -> "It is an odd number!"
+            }
+        }
+    }
+
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOption.kt

@@ -0,0 +1,46 @@
+package com.baeldung.kotlin.arrow
+
+import arrow.core.None
+import arrow.core.Option
+import arrow.core.Some
+import kotlin.math.sqrt
+
+class FunctionalErrorHandlingWithOption {
+
+    fun parseInput(s : String) : Option<Int> = Option.fromNullable(s.toIntOrNull())
+
+    fun isEven(x : Int) : Boolean = x % 2 == 0
+
+    fun biggestDivisor(x: Int) : Int = biggestDivisor(x, 2)
+
+    fun biggestDivisor(x : Int, y : Int) : Int {
+        if(x == y){
+            return 1;
+        }
+        if(x % y == 0){
+            return x / y;
+        }
+        return biggestDivisor(x, y+1)
+    }
+
+    fun isSquareNumber(x : Int) : Boolean {
+        val sqrt: Double = sqrt(x.toDouble())
+        return sqrt % 1.0 == 0.0
+    }
+
+    fun computeWithOption(input : String) : Option<Boolean> {
+        return parseInput(input)
+                .filter(::isEven)
+                .map(::biggestDivisor)
+                .map(::isSquareNumber)
+    }
+
+    fun computeWithOptionClient(input : String) : String{
+        val computeOption = computeWithOption(input)
+
+        return when(computeOption){
+            is None -> "Not an even number!"
+            is Some -> "The greatest divisor is square number: ${computeOption.t}"
+        }
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/kodein/Controller.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.kodein
+
+class Controller(private val service : Service)

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/kodein/Dao.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.kodein
+
+interface Dao

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/kodein/JdbcDao.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.kodein
+
+class JdbcDao : Dao

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/kodein/MongoDao.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.kodein
+
+class MongoDao : Dao

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/kodein/Service.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.kodein
+
+class Service(private val dao: Dao, private val tag: String)

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/mockito/BookService.kt

@@ -0,0 +1,6 @@
+package com.baeldung.kotlin
+
+interface BookService {
+    fun inStock(bookId: Int): Boolean
+    fun lend(bookId: Int, memberId: Int)
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/mockito/LendBookManager.kt

@@ -0,0 +1,11 @@
+package com.baeldung.kotlin
+
+class LendBookManager(val bookService:BookService) {
+    fun checkout(bookId: Int, memberId: Int) {
+        if(bookService.inStock(bookId)) {
+            bookService.lend(bookId, memberId)
+        } else {
+            throw IllegalStateException("Book is not available")
+        }
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/AnnotatedServer.kt

@@ -0,0 +1,73 @@
+package com.baeldung.kovert
+
+import io.vertx.ext.web.Router
+import io.vertx.ext.web.RoutingContext
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.core.HttpVerb
+import uy.kohesive.kovert.core.Location
+import uy.kohesive.kovert.core.Verb
+import uy.kohesive.kovert.core.VerbAlias
+import uy.kohesive.kovert.vertx.bindController
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+
+class AnnotatedServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(AnnotatedServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            AnnotatedServer().start()
+        }
+    }
+
+    @VerbAlias("show", HttpVerb.GET)
+    class AnnotatedController {
+        fun RoutingContext.showStringById(id: String) = id
+
+        @Verb(HttpVerb.GET)
+        @Location("/ping/:id")
+        fun RoutingContext.ping(id: String) = id
+    }
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", AnnotatedServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+            bindController(AnnotatedController(), "api")
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/ErrorServer.kt

@@ -0,0 +1,75 @@
+package com.baeldung.kovert
+
+import io.vertx.ext.web.Router
+import io.vertx.ext.web.RoutingContext
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.core.HttpErrorCode
+import uy.kohesive.kovert.core.HttpErrorCodeWithBody
+import uy.kohesive.kovert.core.HttpErrorForbidden
+import uy.kohesive.kovert.vertx.bindController
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+
+class ErrorServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(ErrorServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            ErrorServer().start()
+        }
+    }
+
+    class ErrorController {
+        fun RoutingContext.getForbidden() {
+            throw HttpErrorForbidden()
+        }
+        fun RoutingContext.getError() {
+            throw HttpErrorCode("Something went wrong", 590)
+        }
+        fun RoutingContext.getErrorbody() {
+            throw HttpErrorCodeWithBody("Something went wrong", 591, "Body here")
+        }
+    }
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", ErrorServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+            bindController(ErrorController(), "api")
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/JsonServer.kt

@@ -0,0 +1,76 @@
+package com.baeldung.kovert
+
+import com.fasterxml.jackson.annotation.JsonProperty
+import io.vertx.ext.web.Router
+import io.vertx.ext.web.RoutingContext
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.vertx.bindController
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+class JsonServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(JsonServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            JsonServer().start()
+        }
+    }
+
+    data class Person(
+            @JsonProperty("_id")
+            val id: String,
+            val name: String,
+            val job: String
+    )
+
+    class JsonController {
+        fun RoutingContext.getPersonById(id: String) = Person(
+                id = id,
+                name = "Tony Stark",
+                job = "Iron Man"
+        )
+        fun RoutingContext.putPersonById(id: String, person: Person) = person
+    }
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", JsonServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+            bindController(JsonController(), "api")
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/NoopServer.kt

@@ -0,0 +1,57 @@
+package com.baeldung.kovert
+
+import io.vertx.ext.web.Router
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+class NoopServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(NoopServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            NoopServer().start()
+        }
+    }
+
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", NoopServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/SecuredServer.kt

@@ -0,0 +1,68 @@
+package com.baeldung.kovert
+
+import io.vertx.ext.web.Router
+import io.vertx.ext.web.RoutingContext
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.vertx.bindController
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+
+class SecuredServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(SecuredServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            SecuredServer().start()
+        }
+    }
+
+    class SecuredContext(private val routingContext: RoutingContext) {
+        val authenticated = routingContext.request().getHeader("Authorization") == "Secure"
+    }
+
+    class SecuredController {
+        fun SecuredContext.getSecured() = this.authenticated
+    }
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", SecuredServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+            bindController(SecuredController(), "api")
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/kovert/SimpleServer.kt

@@ -0,0 +1,65 @@
+package com.baeldung.kovert
+
+import io.vertx.ext.web.Router
+import io.vertx.ext.web.RoutingContext
+import nl.komponents.kovenant.functional.bind
+import org.kodein.di.Kodein
+import org.kodein.di.conf.global
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import uy.klutter.config.typesafe.ClassResourceConfig
+import uy.klutter.config.typesafe.ReferenceConfig
+import uy.klutter.config.typesafe.kodein.importConfig
+import uy.klutter.config.typesafe.loadConfig
+import uy.klutter.vertx.kodein.KodeinVertx
+import uy.kohesive.kovert.vertx.bindController
+import uy.kohesive.kovert.vertx.boot.KodeinKovertVertx
+import uy.kohesive.kovert.vertx.boot.KovertVerticle
+import uy.kohesive.kovert.vertx.boot.KovertVerticleModule
+import uy.kohesive.kovert.vertx.boot.KovertVertx
+
+
+class SimpleServer {
+    companion object {
+        private val LOG: Logger = LoggerFactory.getLogger(SimpleServer::class.java)
+
+        @JvmStatic
+        fun main(args: Array<String>) {
+            SimpleServer().start()
+        }
+    }
+
+    class SimpleController {
+        fun RoutingContext.getStringById(id: String) = id
+        fun RoutingContext.get_truncatedString_by_id(id: String, length: Int = 1) = id.subSequence(0, length)
+    }
+
+    fun start() {
+        Kodein.global.addImport(Kodein.Module {
+            importConfig(loadConfig(ClassResourceConfig("/kovert.conf", SimpleServer::class.java), ReferenceConfig())) {
+                import("kovert.vertx", KodeinKovertVertx.configModule)
+                import("kovert.server", KovertVerticleModule.configModule)
+            }
+
+            // includes jackson ObjectMapper to match compatibility with Vertx, app logging via Vertx facade to Slf4j
+            import(KodeinVertx.moduleWithLoggingToSlf4j)
+            // Kovert boot
+            import(KodeinKovertVertx.module)
+            import(KovertVerticleModule.module)
+        })
+
+        val initControllers = fun Router.() {
+            bindController(SimpleController(), "api")
+        }
+
+        // startup asynchronously...
+        KovertVertx.start() bind { vertx ->
+            KovertVerticle.deploy(vertx, routerInit = initControllers)
+        } success { deploymentId ->
+            LOG.warn("Deployment complete.")
+        } fail { error ->
+            LOG.error("Deployment failed!", error)
+        }
+
+    }
+}

kotlin-libraries/src/main/kotlin/com/baeldung/ktor/APIServer.kt

@@ -0,0 +1,73 @@
+@file:JvmName("APIServer")
+
+
+import io.ktor.application.call
+import io.ktor.application.install
+import io.ktor.features.CallLogging
+import io.ktor.features.ContentNegotiation
+import io.ktor.features.DefaultHeaders
+import io.ktor.gson.gson
+import io.ktor.request.path
+import io.ktor.request.receive
+import io.ktor.response.respond
+import io.ktor.routing.*
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.netty.Netty
+import org.slf4j.event.Level
+
+data class Author(val name: String, val website: String)
+data class ToDo(var id: Int, val name: String, val description: String, val completed: Boolean)
+
+fun main(args: Array<String>) {
+
+    val toDoList = ArrayList<ToDo>();
+    val jsonResponse = """{
+            "id": 1,
+            "task": "Pay waterbill",
+            "description": "Pay water bill today",
+        }"""
+
+
+    embeddedServer(Netty, 8080) {
+        install(DefaultHeaders) {
+            header("X-Developer", "Baeldung")
+        }
+        install(CallLogging) {
+            level = Level.DEBUG
+            filter { call -> call.request.path().startsWith("/todo") }
+            filter { call -> call.request.path().startsWith("/author") }
+        }
+        install(ContentNegotiation) {
+            gson {
+                setPrettyPrinting()
+            }
+        }
+        routing() {
+            route("/todo") {
+                post {
+                    var toDo = call.receive<ToDo>();
+                    toDo.id = toDoList.size;
+                    toDoList.add(toDo);
+                    call.respond("Added")
+
+                }
+                delete("/{id}") {
+                    call.respond(toDoList.removeAt(call.parameters["id"]!!.toInt()));
+                }
+                get("/{id}") {
+
+                    call.respond(toDoList[call.parameters["id"]!!.toInt()]);
+                }
+                get {
+                    call.respond(toDoList);
+                }
+            }
+        get("/author"){
+            call.respond(Author("Baeldung","baeldung.com"));
+
+        }
+
+
+        }
+    }.start(wait = true)
+}

kotlin-libraries/src/main/resources/kovert.conf

@@ -0,0 +1,15 @@
+{
+   kovert: {
+       vertx: {
+            clustered: false
+       }
+       server: {
+           listeners: [
+                 {
+                       host: "0.0.0.0"
+                       port: "8000"
+                 }
+           ]
+       }
+   }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/klaxon/KlaxonUnitTest.kt

@@ -0,0 +1,163 @@
+package com.baeldung.klaxon
+
+import com.beust.klaxon.JsonArray
+import com.beust.klaxon.JsonObject
+import com.beust.klaxon.JsonReader
+import com.beust.klaxon.Klaxon
+import com.beust.klaxon.Parser
+import com.beust.klaxon.PathMatcher
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.SoftAssertions.assertSoftly
+import org.junit.Assert
+import org.junit.jupiter.api.Test
+import java.io.StringReader
+import java.util.regex.Pattern
+
+class KlaxonUnitTest {
+
+    @Test
+    fun giveProduct_whenSerialize_thenGetJsonString() {
+        val product = Product("HDD")
+        val result = Klaxon().toJsonString(product)
+
+        assertThat(result).isEqualTo("""{"name" : "HDD"}""")
+    }
+
+    @Test
+    fun giveJsonString_whenDeserialize_thenGetProduct() {
+        val result = Klaxon().parse<Product>("""
+            {
+                "name" : "RAM"
+            }
+        """)
+
+        assertThat(result?.name).isEqualTo("RAM")
+    }
+
+    @Test
+    fun giveCustomProduct_whenSerialize_thenGetJsonString() {
+        val product = CustomProduct("HDD", 1)
+        val result = Klaxon().toJsonString(product)
+
+        assertThat(result).isEqualTo("""{"productName" : "HDD"}""")
+    }
+
+    @Test
+    fun giveJsonArray_whenStreaming_thenGetProductArray() {
+        val jsonArray = """
+        [
+            { "name" : "HDD", "capacityInGb" : 512 },
+            { "name" : "RAM", "capacityInGb" : 16 }
+        ]"""
+        val expectedArray = arrayListOf(ProductData("HDD", 512),
+                ProductData("RAM", 16))
+        val klaxon = Klaxon()
+        val productArray = arrayListOf<ProductData>()
+        JsonReader(StringReader(jsonArray)).use { reader ->
+            reader.beginArray {
+                while (reader.hasNext()) {
+                    val product = klaxon.parse<ProductData>(reader)
+                    productArray.add(product!!)
+                }
+            }
+        }
+
+        assertThat(productArray).hasSize(2).isEqualTo(expectedArray)
+    }
+
+    @Test
+    fun giveJsonString_whenParser_thenGetJsonObject() {
+        val jsonString = StringBuilder("""
+            {
+                "name" : "HDD",
+                "capacityInGb" : 512,
+                "sizeInInch" : 2.5
+            }
+        """)
+        val parser = Parser()
+        val json = parser.parse(jsonString) as JsonObject
+
+        assertThat(json).hasSize(3).containsEntry("name", "HDD").containsEntry("capacityInGb", 512).containsEntry("sizeInInch", 2.5)
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    @Test
+    fun giveJsonStringArray_whenParser_thenGetJsonArray() {
+        val jsonString = StringBuilder("""
+        [
+            { "name" : "SDD" },
+            { "madeIn" : "Taiwan" },
+            { "warrantyInYears" : 5 }
+        ]""")
+        val parser = Parser()
+        val json = parser.parse(jsonString) as JsonArray<JsonObject>
+
+        assertSoftly({ softly ->
+            softly.assertThat(json).hasSize(3)
+            softly.assertThat(json[0]["name"]).isEqualTo("SDD")
+            softly.assertThat(json[1]["madeIn"]).isEqualTo("Taiwan")
+            softly.assertThat(json[2]["warrantyInYears"]).isEqualTo(5)
+        })
+    }
+
+    @Test
+    fun givenJsonString_whenStreaming_thenProcess() {
+        val jsonString = """
+        {
+             "name" : "HDD",
+             "madeIn" : "Taiwan",
+             "warrantyInYears" : 5
+             "hasStock" : true
+             "capacitiesInTb" : [ 1, 2 ],
+             "features" : { "cacheInMb" : 64, "speedInRpm" : 7200 }
+        }"""
+
+        JsonReader(StringReader(jsonString)).use { reader ->
+            reader.beginObject {
+                while (reader.hasNext()) {
+                    val readName = reader.nextName()
+                    when (readName) {
+                        "name" -> assertThat(reader.nextString()).isEqualTo("HDD")
+                        "madeIn" -> assertThat(reader.nextString()).isEqualTo("Taiwan")
+                        "warrantyInYears" -> assertThat(reader.nextInt()).isEqualTo(5)
+                        "hasStock" -> assertThat(reader.nextBoolean()).isEqualTo(true)
+                        "capacitiesInTb" -> assertThat(reader.nextArray()).contains(1, 2)
+                        "features" -> assertThat(reader.nextObject()).containsEntry("cacheInMb", 64).containsEntry("speedInRpm", 7200)
+                        else -> Assert.fail("Unexpected name: $readName")
+                    }
+                }
+            }
+        }
+
+    }
+
+    @Test
+    fun givenDiskInventory_whenRegexMatches_thenGetTypes() {
+        val jsonString = """
+    {
+       "inventory" : {
+           "disks" : [
+               {
+                   "type" : "HDD",
+                   "sizeInGb" : 1000
+               },
+               {
+                   "type" : "SDD",
+                   "sizeInGb" : 512
+               }
+           ]
+       }
+    }"""
+        val pathMatcher = object : PathMatcher {
+            override fun pathMatches(path: String) = Pattern.matches(".*inventory.*disks.*type.*", path)
+
+            override fun onMatch(path: String, value: Any) {
+                when (path) {
+                    "$.inventory.disks[0].type" -> assertThat(value).isEqualTo("HDD")
+                    "$.inventory.disks[1].type" -> assertThat(value).isEqualTo("SDD")
+                }
+            }
+        }
+        Klaxon().pathMatcher(pathMatcher).parseJsonObject(StringReader(jsonString))
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalDataTypes.kt

@@ -0,0 +1,143 @@
+package com.baeldung.kotlin.arrow
+
+import arrow.core.*
+import org.junit.Assert
+import org.junit.Test
+
+class FunctionalDataTypes {
+
+    @Test
+    fun whenIdCreated_thanValueIsPresent(){
+        val id = Id("foo")
+        val justId = Id.just("foo");
+
+        Assert.assertEquals("foo", id.extract())
+        Assert.assertEquals(justId, id)
+    }
+
+    fun length(s : String) : Int = s.length
+
+    fun isBigEnough(i : Int) : Boolean = i > 10
+
+    @Test
+    fun whenIdCreated_thanMapIsAssociative(){
+        val foo = Id("foo")
+
+        val map1 = foo.map(::length)
+                .map(::isBigEnough)
+        val map2 = foo.map { s -> isBigEnough(length(s)) }
+
+        Assert.assertEquals(map1, map2)
+    }
+
+    fun lengthId(s : String) : Id<Int> = Id.just(length(s))
+
+    fun isBigEnoughId(i : Int) : Id<Boolean> = Id.just(isBigEnough(i))
+
+    @Test
+    fun whenIdCreated_thanFlatMapIsAssociative(){
+        val bar = Id("bar")
+
+        val flatMap = bar.flatMap(::lengthId)
+            .flatMap(::isBigEnoughId)
+        val flatMap1 = bar.flatMap { s -> lengthId(s).flatMap(::isBigEnoughId) }
+
+        Assert.assertEquals(flatMap, flatMap1)
+    }
+
+    @Test
+    fun whenOptionCreated_thanValueIsPresent(){
+        val factory = Option.just(42)
+        val constructor = Option(42)
+        val emptyOptional = Option.empty<Integer>()
+        val fromNullable = Option.fromNullable(null)
+
+        Assert.assertEquals(42, factory.getOrElse { -1 })
+        Assert.assertEquals(factory, constructor)
+        Assert.assertEquals(emptyOptional, fromNullable)
+    }
+
+    @Test
+    fun whenOptionCreated_thanConstructorDifferFromFactory(){
+        val constructor : Option<String?> = Option(null)
+        val fromNullable : Option<String?> = Option.fromNullable(null)
+
+        try{
+            constructor.map { s -> s!!.length }
+            Assert.fail()
+        } catch (e : KotlinNullPointerException){
+            fromNullable.map { s->s!!.length }
+        }
+        Assert.assertNotEquals(constructor, fromNullable)
+    }
+
+    fun wrapper(x : Integer?) : Option<Int> = if (x == null) Option.just(-1) else Option.just(x.toInt())
+
+    @Test
+    fun whenOptionFromNullableCreated_thanItBreaksLeftIdentity(){
+        val optionFromNull = Option.fromNullable(null)
+
+        Assert.assertNotEquals(optionFromNull.flatMap(::wrapper), wrapper(null))
+    }
+
+    @Test
+    fun whenEitherCreated_thanOneValueIsPresent(){
+        val rightOnly : Either<String,Int> = Either.right(42)
+        val leftOnly : Either<String,Int> = Either.left("foo")
+
+        Assert.assertTrue(rightOnly.isRight())
+        Assert.assertTrue(leftOnly.isLeft())
+        Assert.assertEquals(42, rightOnly.getOrElse { -1 })
+        Assert.assertEquals(-1, leftOnly.getOrElse { -1 })
+
+        Assert.assertEquals(0, rightOnly.map { it % 2 }.getOrElse { -1 })
+        Assert.assertEquals(-1, leftOnly.map { it % 2 }.getOrElse { -1 })
+        Assert.assertTrue(rightOnly.flatMap { Either.Right(it % 2) }.isRight())
+        Assert.assertTrue(leftOnly.flatMap { Either.Right(it % 2) }.isLeft())
+    }
+
+    @Test
+    fun whenEvalNowUsed_thenMapEvaluatedLazily(){
+        val now = Eval.now(1)
+        Assert.assertEquals(1, now.value())
+
+        var counter : Int = 0
+        val map = now.map { x -> counter++; x+1 }
+        Assert.assertEquals(0, counter)
+        
+        val value = map.value()
+        Assert.assertEquals(2, value)
+        Assert.assertEquals(1, counter)
+    }
+
+    @Test
+    fun whenEvalLaterUsed_theResultIsMemoized(){
+        var counter : Int = 0
+        val later = Eval.later { counter++; counter }
+        Assert.assertEquals(0, counter)
+
+        val firstValue = later.value()
+        Assert.assertEquals(1, firstValue)
+        Assert.assertEquals(1, counter)
+
+        val secondValue = later.value()
+        Assert.assertEquals(1, secondValue)
+        Assert.assertEquals(1, counter)
+    }
+
+    @Test
+    fun whenEvalAlwaysUsed_theResultIsNotMemoized(){
+        var counter : Int = 0
+        val later = Eval.always { counter++; counter }
+        Assert.assertEquals(0, counter)
+
+        val firstValue = later.value()
+        Assert.assertEquals(1, firstValue)
+        Assert.assertEquals(1, counter)
+
+        val secondValue = later.value()
+        Assert.assertEquals(2, secondValue)
+        Assert.assertEquals(2, counter)
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEitherTest.kt

@@ -0,0 +1,68 @@
+package com.baeldung.kotlin.arrow
+
+import arrow.core.Either
+import com.baeldung.kotlin.arrow.FunctionalErrorHandlingWithEither.ComputeProblem.NotANumber
+import com.baeldung.kotlin.arrow.FunctionalErrorHandlingWithEither.ComputeProblem.OddNumber
+import org.junit.Assert
+import org.junit.Test
+
+class FunctionalErrorHandlingWithEitherTest {
+
+    val operator = FunctionalErrorHandlingWithEither()
+
+    @Test
+    fun givenInvalidInput_whenComputeInvoked_NotANumberIsPresent(){
+        val computeWithEither = operator.computeWithEither("bar")
+
+        Assert.assertTrue(computeWithEither.isLeft())
+        when(computeWithEither){
+            is Either.Left -> when(computeWithEither.a){
+                NotANumber -> "Ok."
+                else -> Assert.fail()
+            }
+            else -> Assert.fail()
+        }
+    }
+
+    @Test
+    fun givenOddNumberInput_whenComputeInvoked_OddNumberIsPresent(){
+        val computeWithEither = operator.computeWithEither("121")
+
+        Assert.assertTrue(computeWithEither.isLeft())
+        when(computeWithEither){
+            is Either.Left -> when(computeWithEither.a){
+                OddNumber -> "Ok."
+                else -> Assert.fail()
+            }
+            else -> Assert.fail()
+        }
+    }
+
+    @Test
+    fun givenEvenNumberWithoutSquare_whenComputeInvoked_OddNumberIsPresent(){
+        val computeWithEither = operator.computeWithEither("100")
+
+        Assert.assertTrue(computeWithEither.isRight())
+        when(computeWithEither){
+            is Either.Right -> when(computeWithEither.b){
+                false -> "Ok."
+                else -> Assert.fail()
+            }
+            else -> Assert.fail()
+        }
+    }
+
+    @Test
+    fun givenEvenNumberWithSquare_whenComputeInvoked_OddNumberIsPresent(){
+        val computeWithEither = operator.computeWithEither("98")
+
+        Assert.assertTrue(computeWithEither.isRight())
+        when(computeWithEither){
+            is Either.Right -> when(computeWithEither.b){
+                true -> "Ok."
+                else -> Assert.fail()
+            }
+            else -> Assert.fail()
+        }
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOptionTest.kt

@@ -0,0 +1,34 @@
+package com.baeldung.kotlin.arrow
+
+import org.junit.Assert
+import org.junit.Test
+
+class FunctionalErrorHandlingWithOptionTest {
+
+    val operator = FunctionalErrorHandlingWithOption()
+
+    @Test
+    fun givenInvalidInput_thenErrorMessageIsPresent(){
+        val useComputeOption = operator.computeWithOptionClient("foo")
+        Assert.assertEquals("Not an even number!", useComputeOption)
+    }
+
+    @Test
+    fun givenOddNumberInput_thenErrorMessageIsPresent(){
+        val useComputeOption = operator.computeWithOptionClient("539")
+        Assert.assertEquals("Not an even number!",useComputeOption)
+    }
+
+    @Test
+    fun givenEvenNumberInputWithNonSquareNum_thenFalseMessageIsPresent(){
+        val useComputeOption = operator.computeWithOptionClient("100")
+        Assert.assertEquals("The greatest divisor is square number: false",useComputeOption)
+    }
+
+    @Test
+    fun givenEvenNumberInputWithSquareNum_thenTrueMessageIsPresent(){
+        val useComputeOption = operator.computeWithOptionClient("242")
+        Assert.assertEquals("The greatest divisor is square number: true",useComputeOption)
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/dates/CreateDateUnitTest.kt

@@ -0,0 +1,34 @@
+package com.baeldung.kotlin.dates
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+
+class CreateDateUnitTest {
+
+    @Test
+    fun givenString_whenDefaultFormat_thenCreated() {
+
+        var date = LocalDate.parse("2018-12-31")
+
+        assertThat(date).isEqualTo("2018-12-31")
+    }
+
+    @Test
+    fun givenString_whenCustomFormat_thenCreated() {
+
+        var formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy")
+        var date = LocalDate.parse("31-12-2018", formatter)
+
+        assertThat(date).isEqualTo("2018-12-31")
+    }
+
+    @Test
+    fun givenYMD_whenUsingOf_thenCreated() {
+        var date = LocalDate.of(2018, 12, 31)
+
+        assertThat(date).isEqualTo("2018-12-31")
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/dates/ExtractDateUnitTest.kt

@@ -0,0 +1,29 @@
+package com.baeldung.kotlin.dates
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import java.time.DayOfWeek
+import java.time.LocalDate
+import java.time.Month
+
+class ExtractDateUnitTest {
+
+    @Test
+    fun givenDate_thenExtractedYMD() {
+        var date = LocalDate.parse("2018-12-31")
+
+        assertThat(date.year).isEqualTo(2018)
+        assertThat(date.month).isEqualTo(Month.DECEMBER)
+        assertThat(date.dayOfMonth).isEqualTo(31)
+    }
+
+    @Test
+    fun givenDate_thenExtractedEraDowDoy() {
+        var date = LocalDate.parse("2018-12-31")
+
+        assertThat(date.era.toString()).isEqualTo("CE")
+        assertThat(date.dayOfWeek).isEqualTo(DayOfWeek.MONDAY)
+        assertThat(date.dayOfYear).isEqualTo(365)
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/dates/FormatDateUnitTest.kt

@@ -0,0 +1,29 @@
+package com.baeldung.kotlin.dates
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+
+class FormatDateUnitTest {
+
+    @Test
+    fun givenDate_whenDefaultFormat_thenFormattedString() {
+
+        var date = LocalDate.parse("2018-12-31")
+
+        assertThat(date.toString()).isEqualTo("2018-12-31")
+    }
+
+    @Test
+    fun givenDate_whenCustomFormat_thenFormattedString() {
+
+        var date = LocalDate.parse("2018-12-31")
+
+        var formatter = DateTimeFormatter.ofPattern("dd-MMMM-yyyy")
+        var formattedDate = date.format(formatter)
+
+        assertThat(formattedDate).isEqualTo("31-December-2018")
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/dates/PeriodDateUnitTest.kt

@@ -0,0 +1,48 @@
+package com.baeldung.kotlin.dates
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.Period
+
+class PeriodDateUnitTest {
+
+    @Test
+    fun givenYMD_thenCreatePeriod() {
+        var period = Period.of(1, 2, 3)
+
+        assertThat(period.toString()).isEqualTo("P1Y2M3D")
+    }
+
+    @Test
+    fun givenPeriod_whenAdd_thenModifiedDate() {
+        var period = Period.of(1, 2, 3)
+
+        var date = LocalDate.of(2018, 6, 25)
+        var modifiedDate = date.plus(period)
+
+        assertThat(modifiedDate).isEqualTo("2019-08-28")
+    }
+
+    @Test
+    fun givenPeriod_whenSubtracted_thenModifiedDate() {
+        var period = Period.of(1, 2, 3)
+
+        var date = LocalDate.of(2018, 6, 25)
+        var modifiedDate = date.minus(period)
+
+        assertThat(modifiedDate).isEqualTo("2017-04-22")
+    }
+
+    @Test
+    fun givenTwoDate_whenUsingBetween_thenDiffOfDates() {
+
+        var date1 = LocalDate.parse("2018-06-25")
+        var date2 = LocalDate.parse("2018-12-25")
+
+        var period = Period.between(date1, date2)
+
+        assertThat(period.toString()).isEqualTo("P6M")
+    }
+
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/exposed/ExposedTest.kt

@@ -0,0 +1,333 @@
+package com.baeldung.kotlin.exposed
+
+import org.jetbrains.exposed.dao.*
+import org.jetbrains.exposed.sql.*
+import org.jetbrains.exposed.sql.transactions.TransactionManager
+import org.jetbrains.exposed.sql.transactions.transaction
+import org.junit.Test
+import java.sql.DriverManager
+import kotlin.test.*
+
+class ExposedTest {
+
+    @Test
+    fun whenH2Database_thenConnectionSuccessful() {
+        val database = Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        transaction {
+            assertEquals(1.4.toBigDecimal(), database.version)
+            assertEquals("h2", database.vendor)
+        }
+    }
+
+    @Test
+    fun whenH2DatabaseWithCredentials_thenConnectionSuccessful() {
+        Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver", user = "myself", password = "secret")
+    }
+
+    @Test
+    fun whenH2DatabaseWithManualConnection_thenConnectionSuccessful() {
+        var connected = false
+        Database.connect({ connected = true; DriverManager.getConnection("jdbc:h2:mem:test;MODE=MySQL") })
+        assertEquals(false, connected)
+        transaction {
+            addLogger(StdOutSqlLogger)
+            assertEquals(false, connected)
+            SchemaUtils.create(Cities)
+            assertEquals(true, connected)
+        }
+    }
+
+    @Test
+    fun whenManualCommit_thenOk() {
+        Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        transaction {
+            assertTrue(this is Transaction)
+            commit()
+            commit()
+            commit()
+        }
+    }
+
+    @Test
+    fun whenInsert_thenGeneratedKeys() {
+        Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        transaction {
+            SchemaUtils.create(StarWarsFilms)
+            val id = StarWarsFilms.insertAndGetId {
+                it[name] = "The Last Jedi"
+                it[sequelId] = 8
+                it[director] = "Rian Johnson"
+            }
+            assertEquals(1, id.value)
+            val insert = StarWarsFilms.insert {
+                it[name] = "The Force Awakens"
+                it[sequelId] = 7
+                it[director] = "J.J. Abrams"
+            }
+            assertEquals(2, insert[StarWarsFilms.id]?.value)
+            val selectAll = StarWarsFilms.selectAll()
+            selectAll.forEach {
+                assertTrue { it[StarWarsFilms.sequelId] >= 7 }
+            }
+            StarWarsFilms.slice(StarWarsFilms.name, StarWarsFilms.director).selectAll()
+                    .forEach {
+                        assertTrue { it[StarWarsFilms.name].startsWith("The") }
+                    }
+            val select = StarWarsFilms.select { (StarWarsFilms.director like "J.J.%") and (StarWarsFilms.sequelId eq 7) }
+            assertEquals(1, select.count())
+            StarWarsFilms.update ({ StarWarsFilms.sequelId eq 8 }) {
+                it[name] = "Episode VIII – The Last Jedi"
+                with(SqlExpressionBuilder) {
+                    it.update(StarWarsFilms.sequelId, StarWarsFilms.sequelId + 1)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun whenForeignKey_thenAutoJoin() {
+        Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        transaction {
+            addLogger(StdOutSqlLogger)
+            SchemaUtils.create(StarWarsFilms, Players)
+            StarWarsFilms.insert {
+                it[name] = "The Last Jedi"
+                it[sequelId] = 8
+                it[director] = "Rian Johnson"
+            }
+            StarWarsFilms.insert {
+                it[name] = "The Force Awakens"
+                it[sequelId] = 7
+                it[director] = "J.J. Abrams"
+            }
+            Players.insert {
+                it[name] = "Mark Hamill"
+                it[sequelId] = 7
+            }
+            Players.insert {
+                it[name] = "Mark Hamill"
+                it[sequelId] = 8
+            }
+            val simpleInnerJoin = (StarWarsFilms innerJoin Players).selectAll()
+            assertEquals(2, simpleInnerJoin.count())
+            simpleInnerJoin.forEach {
+                assertNotNull(it[StarWarsFilms.name])
+                assertEquals(it[StarWarsFilms.sequelId], it[Players.sequelId])
+                assertEquals("Mark Hamill", it[Players.name])
+            }
+            val innerJoinWithCondition = (StarWarsFilms innerJoin Players)
+                    .select { StarWarsFilms.sequelId eq Players.sequelId }
+            assertEquals(2, innerJoinWithCondition.count())
+            innerJoinWithCondition.forEach {
+                assertNotNull(it[StarWarsFilms.name])
+                assertEquals(it[StarWarsFilms.sequelId], it[Players.sequelId])
+                assertEquals("Mark Hamill", it[Players.name])
+            }
+            val complexInnerJoin = Join(StarWarsFilms, Players, joinType = JoinType.INNER, onColumn = StarWarsFilms.sequelId, otherColumn = Players.sequelId, additionalConstraint = {
+                StarWarsFilms.sequelId eq 8
+            }).selectAll()
+            assertEquals(1, complexInnerJoin.count())
+            complexInnerJoin.forEach {
+                assertNotNull(it[StarWarsFilms.name])
+                assertEquals(it[StarWarsFilms.sequelId], it[Players.sequelId])
+                assertEquals("Mark Hamill", it[Players.name])
+            }
+
+        }
+    }
+
+    @Test
+    fun whenJoinWithAlias_thenFun() {
+        Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        transaction {
+            addLogger(StdOutSqlLogger)
+            SchemaUtils.create(StarWarsFilms, Players)
+            StarWarsFilms.insert {
+                it[name] = "The Last Jedi"
+                it[sequelId] = 8
+                it[director] = "Rian Johnson"
+            }
+            StarWarsFilms.insert {
+                it[name] = "The Force Awakens"
+                it[sequelId] = 7
+                it[director] = "J.J. Abrams"
+            }
+            val sequel = StarWarsFilms.alias("sequel")
+            Join(StarWarsFilms, sequel,
+                    additionalConstraint = { sequel[StarWarsFilms.sequelId] eq StarWarsFilms.sequelId + 1 })
+                    .selectAll().forEach {
+                assertEquals(it[sequel[StarWarsFilms.sequelId]], it[StarWarsFilms.sequelId] + 1)
+            }
+        }
+    }
+
+    @Test
+    fun whenEntity_thenDAO() {
+        val database = Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        val connection = database.connector.invoke() //Keep a connection open so the DB is not destroyed after the first transaction
+        val inserted = transaction {
+            addLogger(StdOutSqlLogger)
+            SchemaUtils.create(StarWarsFilms, Players)
+            val theLastJedi = StarWarsFilm.new {
+                name = "The Last Jedi"
+                sequelId = 8
+                director = "Rian Johnson"
+            }
+            assertFalse(TransactionManager.current().entityCache.inserts.isEmpty())
+            assertEquals(1, theLastJedi.id.value) //Reading this causes a flush
+            assertTrue(TransactionManager.current().entityCache.inserts.isEmpty())
+            theLastJedi
+        }
+        transaction {
+            val theLastJedi = StarWarsFilm.findById(1)
+            assertNotNull(theLastJedi)
+            assertEquals(inserted.id, theLastJedi?.id)
+        }
+        connection.close()
+    }
+
+    @Test
+    fun whenManyToOne_thenNavigation() {
+        val database = Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        val connection = database.connector.invoke()
+        transaction {
+            addLogger(StdOutSqlLogger)
+            SchemaUtils.create(StarWarsFilms, Players, Users, UserRatings)
+            val theLastJedi = StarWarsFilm.new {
+                name = "The Last Jedi"
+                sequelId = 8
+                director = "Rian Johnson"
+            }
+            val someUser = User.new {
+                name = "Some User"
+            }
+            val rating = UserRating.new {
+                value = 9
+                user = someUser
+                film = theLastJedi
+            }
+            assertEquals(theLastJedi, rating.film)
+            assertEquals(someUser, rating.user)
+            assertEquals(rating, theLastJedi.ratings.first())
+        }
+        transaction {
+            val theLastJedi = StarWarsFilm.find { StarWarsFilms.sequelId eq 8 }.first()
+            val ratings = UserRating.find { UserRatings.film eq theLastJedi.id }
+            assertEquals(1, ratings.count())
+            val rating = ratings.first()
+            assertEquals("Some User", rating.user.name)
+            assertEquals(rating, theLastJedi.ratings.first())
+            UserRating.new {
+                value = 8
+                user = rating.user
+                film = theLastJedi
+            }
+            assertEquals(2, theLastJedi.ratings.count())
+        }
+        connection.close()
+    }
+
+    @Test
+    fun whenManyToMany_thenAssociation() {
+        val database = Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver")
+        val connection = database.connector.invoke()
+        val film = transaction {
+            SchemaUtils.create(StarWarsFilms)
+            StarWarsFilm.new {
+                name = "The Last Jedi"
+                sequelId = 8
+                director = "Rian Johnson"
+            }
+        }
+
+        val actor = transaction {
+            SchemaUtils.create(Actors)
+            Actor.new {
+                firstname = "Daisy"
+                lastname = "Ridley"
+            }
+        }
+
+        transaction {
+            SchemaUtils.create(StarWarsFilmActors)
+            film.actors = SizedCollection(listOf(actor))
+        }
+        connection.close()
+    }
+
+}
+
+object Cities: IntIdTable() {
+    val name = varchar("name", 50)
+}
+
+object StarWarsFilms_Simple : Table() {
+    val id = integer("id").autoIncrement().primaryKey()
+    val sequelId = integer("sequel_id").uniqueIndex()
+    val name = varchar("name", 50)
+    val director = varchar("director", 50)
+}
+
+object StarWarsFilms : IntIdTable() {
+    val sequelId = integer("sequel_id").uniqueIndex()
+    val name = varchar("name", 50)
+    val director = varchar("director", 50)
+}
+
+object Players : Table() {
+    //val sequelId = integer("sequel_id").uniqueIndex().references(StarWarsFilms.sequelId)
+    val sequelId = reference("sequel_id", StarWarsFilms.sequelId).uniqueIndex()
+    //val filmId = reference("film_id", StarWarsFilms).nullable()
+    val name = varchar("name", 50)
+}
+
+class StarWarsFilm(id: EntityID<Int>) : Entity<Int>(id) {
+    companion object : EntityClass<Int, StarWarsFilm>(StarWarsFilms)
+
+    var sequelId by StarWarsFilms.sequelId
+    var name     by StarWarsFilms.name
+    var director by StarWarsFilms.director
+    var actors   by Actor via StarWarsFilmActors
+    val ratings  by UserRating referrersOn UserRatings.film
+}
+
+object Users: IntIdTable() {
+    val name = varchar("name", 50)
+}
+
+object UserRatings: IntIdTable() {
+    val value = long("value")
+    val film  = reference("film", StarWarsFilms)
+    val user  = reference("user", Users)
+}
+
+class User(id: EntityID<Int>): IntEntity(id) {
+    companion object : IntEntityClass<User>(Users)
+
+    var name by Users.name
+}
+
+class UserRating(id: EntityID<Int>): IntEntity(id) {
+    companion object : IntEntityClass<UserRating>(UserRatings)
+
+    var value by UserRatings.value
+    var film  by StarWarsFilm referencedOn UserRatings.film
+    var user  by User         referencedOn UserRatings.user
+}
+
+object Actors: IntIdTable() {
+    val firstname = varchar("firstname", 50)
+    val lastname = varchar("lastname", 50)
+}
+
+class Actor(id: EntityID<Int>): IntEntity(id) {
+    companion object : IntEntityClass<Actor>(Actors)
+
+    var firstname by Actors.firstname
+    var lastname by Actors.lastname
+}
+
+object StarWarsFilmActors : Table() {
+    val starWarsFilm = reference("starWarsFilm", StarWarsFilms).primaryKey(0)
+    val actor = reference("actor", Actors).primaryKey(1)
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/junit5/Calculator.kt

@@ -0,0 +1,17 @@
+package com.baeldung.kotlin.junit5
+
+class Calculator {
+    fun add(a: Int, b: Int) = a + b
+
+    fun divide(a: Int, b: Int) = if (b == 0) {
+        throw DivideByZeroException(a)
+    } else {
+        a / b
+    }
+
+    fun square(a: Int) = a * a
+
+    fun squareRoot(a: Int) = Math.sqrt(a.toDouble())
+
+    fun log(base: Int, value: Int) = Math.log(value.toDouble()) / Math.log(base.toDouble())
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/junit5/DivideByZeroException.kt

@@ -0,0 +1,3 @@
+package com.baeldung.kotlin.junit5
+
+class DivideByZeroException(val numerator: Int) : Exception()

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/khttp/KhttpLiveTest.kt

@@ -0,0 +1,153 @@
+package com.baeldung.kotlin.khttp
+
+import khttp.structures.files.FileLike
+import org.json.JSONObject
+import org.junit.Test
+import java.beans.ExceptionListener
+import java.beans.XMLEncoder
+import java.io.*
+import java.lang.Exception
+import java.net.ConnectException
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+import kotlin.test.fail
+
+class KhttpLiveTest {
+
+    @Test
+    fun whenHttpGetRequestIsMade_thenArgsAreReturned() {
+        val response = khttp.get(
+                url = "http://httpbin.org/get",
+                params = mapOf("p1" to "1", "p2" to "2"))
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+    }
+
+    @Test
+    fun whenAlternateHttpGetRequestIsMade_thenArgsAreReturned() {
+        val response = khttp.request(
+                method = "GET",
+                url = "http://httpbin.org/get",
+                params = mapOf("p1" to "1", "p2" to "2"))
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+    }
+
+    @Test
+    fun whenHeadersAreSet_thenHeadersAreSent() {
+        val response = khttp.get(
+                url = "http://httpbin.org/get",
+                headers = mapOf("header1" to "1", "header2" to "2"))
+        val headers = response.jsonObject.getJSONObject("headers")
+
+        assertEquals("1", headers["Header1"])
+        assertEquals("2", headers["Header2"])
+    }
+
+    @Test
+    fun whenHttpPostRequestIsMadeWithJson_thenBodyIsReturned() {
+        val response = khttp.post(
+                url = "http://httpbin.org/post",
+                params = mapOf("p1" to "1", "p2" to "2"),
+                json = mapOf("pr1" to "1", "pr2" to "2"))
+
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+
+        val json = response.jsonObject.getJSONObject("json")
+
+        assertEquals("1", json["pr1"])
+        assertEquals("2", json["pr2"])
+    }
+
+    @Test
+    fun whenHttpPostRequestIsMadeWithMapData_thenBodyIsReturned() {
+        val response = khttp.post(
+                url = "http://httpbin.org/post",
+                params = mapOf("p1" to "1", "p2" to "2"),
+                data = mapOf("pr1" to "1", "pr2" to "2"))
+
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+
+        val form = response.jsonObject.getJSONObject("form")
+
+        assertEquals("1", form["pr1"])
+        assertEquals("2", form["pr2"])
+    }
+
+    @Test
+    fun whenHttpPostRequestIsMadeWithFiles_thenBodyIsReturned() {
+        val response = khttp.post(
+                url = "http://httpbin.org/post",
+                params = mapOf("p1" to "1", "p2" to "2"),
+                files = listOf(
+                        FileLike("file1", "content1"),
+                        FileLike("file2", javaClass.getResource("KhttpTest.class").openStream().readBytes())))
+
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+
+        val files = response.jsonObject.getJSONObject("files")
+
+        assertEquals("content1", files["file1"])
+    }
+
+    @Test
+    fun whenHttpPostRequestIsMadeWithInputStream_thenBodyIsReturned() {
+        val response = khttp.post(
+                url = "http://httpbin.org/post",
+                params = mapOf("p1" to "1", "p2" to "2"),
+                data = ByteArrayInputStream("content!".toByteArray()))
+
+        val args = response.jsonObject.getJSONObject("args")
+
+        assertEquals("1", args["p1"])
+        assertEquals("2", args["p2"])
+
+        assertEquals("content!", response.jsonObject["data"])
+    }
+
+    @Test
+    fun whenHttpPostStreamingRequestIsMade_thenBodyIsReturnedInChunks() {
+        val response = khttp.post(
+                url = "http://httpbin.org/post",
+                stream = true,
+                json = mapOf("pr1" to "1", "pr2" to "2"))
+
+        val baos = ByteArrayOutputStream()
+        response.contentIterator(chunkSize = 10).forEach { arr : ByteArray -> baos.write(arr) }
+        val json = JSONObject(String(baos.toByteArray())).getJSONObject("json")
+
+        assertEquals("1", json["pr1"])
+        assertEquals("2", json["pr2"])
+    }
+
+    @Test
+    fun whenHttpRequestFails_thenExceptionIsThrown() {
+        try {
+            khttp.get(url = "http://localhost/nothing/to/see/here")
+
+            fail("Should have thrown an exception")
+        } catch (e : ConnectException) {
+            //Ok
+        }
+    }
+
+    @Test
+    fun whenHttpNotFound_thenExceptionIsThrown() {
+        val response = khttp.get(url = "http://httpbin.org/nothing/to/see/here")
+
+        assertEquals(404, response.statusCode)
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/kodein/KodeinUnitTest.kt

@@ -0,0 +1,191 @@
+package com.baeldung.kotlin.kodein
+
+import com.github.salomonbrys.kodein.*
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Test
+
+class KodeinUnitTest {
+
+    class InMemoryDao : Dao
+
+    @Test
+    fun whenSingletonBinding_thenSingleInstanceIsCreated() {
+        var created = false
+        val kodein = Kodein {
+            bind<Dao>() with singleton {
+                created = true
+                MongoDao()
+            }
+        }
+
+        assertThat(created).isFalse()
+
+        val dao1: Dao = kodein.instance()
+
+        assertThat(created).isTrue()
+
+        val dao2: Dao = kodein.instance()
+
+        assertThat(dao1).isSameAs(dao2)
+    }
+
+    @Test
+    fun whenFactoryBinding_thenNewInstanceIsCreated() {
+        val kodein = Kodein {
+            bind<Dao>() with singleton { MongoDao() }
+            bind<Service>() with factory { tag: String -> Service(instance(), tag) }
+        }
+        val service1: Service = kodein.with("myTag").instance()
+        val service2: Service = kodein.with("myTag").instance()
+
+        assertThat(service1).isNotSameAs(service2)
+    }
+
+    @Test
+    fun whenProviderBinding_thenNewInstanceIsCreated() {
+        val kodein = Kodein {
+            bind<Dao>() with provider { MongoDao() }
+        }
+        val dao1: Dao = kodein.instance()
+        val dao2: Dao = kodein.instance()
+
+        assertThat(dao1).isNotSameAs(dao2)
+    }
+
+    @Test
+    fun whenTaggedBinding_thenMultipleInstancesOfSameTypeCanBeRegistered() {
+        val kodein = Kodein {
+            bind<Dao>("dao1") with singleton { MongoDao() }
+            bind<Dao>("dao2") with singleton { MongoDao() }
+        }
+        val dao1: Dao = kodein.instance("dao1")
+        val dao2: Dao = kodein.instance("dao2")
+
+        assertThat(dao1).isNotSameAs(dao2)
+    }
+
+    @Test
+    fun whenEagerSingletonBinding_thenCreationIsEager() {
+        var created = false
+        val kodein = Kodein {
+            bind<Dao>() with eagerSingleton {
+                created = true
+                MongoDao()
+            }
+        }
+
+        assertThat(created).isTrue()
+        val dao1: Dao = kodein.instance()
+        val dao2: Dao = kodein.instance()
+
+        assertThat(dao1).isSameAs(dao2)
+    }
+
+    @Test
+    fun whenMultitonBinding_thenInstancesAreReused() {
+        val kodein = Kodein {
+            bind<Dao>() with singleton { MongoDao() }
+            bind<Service>() with multiton { tag: String -> Service(instance(), tag) }
+        }
+        val service1: Service = kodein.with("myTag").instance()
+        val service2: Service = kodein.with("myTag").instance()
+
+        assertThat(service1).isSameAs(service2)
+    }
+
+    @Test
+    fun whenInstanceBinding_thenItIsReused() {
+        val dao = MongoDao()
+        val kodein = Kodein {
+            bind<Dao>() with instance(dao)
+        }
+        val fromContainer: Dao = kodein.instance()
+
+        assertThat(dao).isSameAs(fromContainer)
+    }
+
+    @Test
+    fun whenConstantBinding_thenItIsAvailable() {
+        val kodein = Kodein {
+            constant("magic") with 42
+        }
+        val fromContainer: Int = kodein.instance("magic")
+
+        assertThat(fromContainer).isEqualTo(42)
+    }
+
+    @Test
+    fun whenUsingModules_thenTransitiveDependenciesAreSuccessfullyResolved() {
+        val jdbcModule = Kodein.Module {
+            bind<Dao>() with singleton { JdbcDao() }
+        }
+        val kodein = Kodein {
+            import(jdbcModule)
+            bind<Controller>() with singleton { Controller(instance()) }
+            bind<Service>() with singleton { Service(instance(), "myService") }
+        }
+
+        val dao: Dao = kodein.instance()
+        assertThat(dao).isInstanceOf(JdbcDao::class.java)
+    }
+
+    @Test
+    fun whenComposition_thenBeansAreReUsed() {
+        val persistenceContainer = Kodein {
+            bind<Dao>() with singleton { MongoDao() }
+        }
+        val serviceContainer = Kodein {
+            extend(persistenceContainer)
+            bind<Service>() with singleton { Service(instance(), "myService") }
+        }
+        val fromPersistence: Dao = persistenceContainer.instance()
+        val fromService: Dao = serviceContainer.instance()
+
+        assertThat(fromPersistence).isSameAs(fromService)
+    }
+
+    @Test
+    fun whenOverriding_thenRightBeanIsUsed() {
+        val commonModule = Kodein.Module {
+            bind<Dao>() with singleton { MongoDao() }
+            bind<Service>() with singleton { Service(instance(), "myService") }
+        }
+        val testContainer = Kodein {
+            import(commonModule)
+            bind<Dao>(overrides = true) with singleton { InMemoryDao() }
+        }
+        val dao: Dao = testContainer.instance()
+
+        assertThat(dao).isInstanceOf(InMemoryDao::class.java)
+    }
+
+    @Test
+    fun whenMultiBinding_thenWorks() {
+        val kodein = Kodein {
+            bind() from setBinding<Dao>()
+            bind<Dao>().inSet() with singleton { MongoDao() }
+            bind<Dao>().inSet() with singleton { JdbcDao() }
+        }
+        val daos: Set<Dao> = kodein.instance()
+
+        assertThat(daos.map { it.javaClass as Class<*> }).containsOnly(MongoDao::class.java, JdbcDao::class.java)
+    }
+
+    @Test
+    fun whenInjector_thenWorks() {
+        class Controller2 {
+            private val injector = KodeinInjector()
+            val service: Service by injector.instance()
+            fun injectDependencies(kodein: Kodein) = injector.inject(kodein)
+        }
+
+        val kodein = Kodein {
+            bind<Dao>() with singleton { MongoDao() }
+            bind<Service>() with singleton { Service(instance(), "myService") }
+        }
+        val controller = Controller2()
+        controller.injectDependencies(kodein)
+
+        assertThat(controller.service).isNotNull
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/mockito/LendBookManagerTest.kt

@@ -0,0 +1,30 @@
+package com.baeldung.kotlin;
+
+import org.junit.Test
+import org.mockito.Mockito
+
+class LibraryManagementTest {
+    @Test(expected = IllegalStateException::class)
+    fun whenBookIsNotAvailable_thenAnExceptionIsThrown() {
+        val mockBookService = Mockito.mock(BookService::class.java)
+
+        Mockito.`when`(mockBookService.inStock(100)).thenReturn(false)
+
+        val manager = LendBookManager(mockBookService)
+
+        manager.checkout(100, 1)
+    }
+
+    @Test
+    fun whenBookIsAvailable_thenLendMethodIsCalled() {
+        val mockBookService = Mockito.mock(BookService::class.java)
+
+        Mockito.`when`(mockBookService.inStock(100)).thenReturn(true)
+
+        val manager = LendBookManager(mockBookService)
+
+        manager.checkout(100, 1)
+
+        Mockito.verify(mockBookService).lend(100, 1)
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/mockito/LendBookManagerTestMockitoKotlin.kt

@@ -0,0 +1,32 @@
+package com.baeldung.kotlin;
+
+import com.nhaarman.mockito_kotlin.mock
+import com.nhaarman.mockito_kotlin.verify
+import com.nhaarman.mockito_kotlin.whenever
+import org.junit.Test
+
+class LibraryManagementTestMockitoKotlin {
+    @Test(expected = IllegalStateException::class)
+    fun whenBookIsNotAvailable_thenAnExceptionIsThrown() {
+        val mockBookService = mock<BookService>() 
+
+        whenever(mockBookService.inStock(100)).thenReturn(false)
+
+        val manager = LendBookManager(mockBookService)
+
+        manager.checkout(100, 1)
+    }
+
+    @Test
+    fun whenBookIsAvailable_thenLendMethodIsCalled() {
+        val mockBookService : BookService = mock()
+
+        whenever(mockBookService.inStock(100)).thenReturn(true)
+
+        val manager = LendBookManager(mockBookService)
+
+        manager.checkout(100, 1)
+
+        verify(mockBookService).lend(100, 1)
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/rxkotlin/RxKotlinTest.kt

@@ -0,0 +1,157 @@
+package com.baeldung.kotlin.rxkotlin
+
+import io.reactivex.Maybe
+import io.reactivex.Observable
+import io.reactivex.functions.BiFunction
+import io.reactivex.rxkotlin.*
+import io.reactivex.subjects.PublishSubject
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+
+class RxKotlinTest {
+
+    @Test
+    fun whenBooleanArrayToObserver_thenBooleanObserver() {
+        val observable = listOf(true, false, false).toObservable()
+        observable.test().assertValues(true, false, false)
+    }
+
+    @Test
+    fun whenBooleanArrayToFlowable_thenBooleanFlowable() {
+        val flowable = listOf(true, false, false).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(true, false), listOf(false))
+    }
+
+    @Test
+    fun whenIntArrayToObserver_thenIntObserver() {
+        val observable = listOf(1, 1, 2, 3).toObservable()
+        observable.test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenIntArrayToFlowable_thenIntFlowable() {
+        val flowable = listOf(1, 1, 2, 3).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(1, 1), listOf(2, 3))
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleNoDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMap()
+        assertEquals(mapOf(Pair("a", 4), Pair("b", 2), Pair("c", 3)), map.blockingGet())
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleWithDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMultimap()
+        assertEquals(
+                mapOf(Pair("a", listOf(1, 4)), Pair("b", listOf(2)), Pair("c", listOf(3))),
+                map.blockingGet())
+    }
+
+    @Test
+    fun whenMergeAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.mergeAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenConcatAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.concatAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenSwitchLatest_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.switchLatest()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenMergeAllMaybes_thenObservable() {
+        val subject = PublishSubject.create<Maybe<Int>>()
+        val observable = subject.mergeAllMaybes()
+        val testObserver = observable.test()
+        subject.onNext(Maybe.just(1))
+        subject.onNext(Maybe.just(2))
+        subject.onNext(Maybe.empty())
+        testObserver.assertValues(1, 2)
+        subject.onNext(Maybe.error(Exception("")))
+        subject.onNext(Maybe.just(3))
+        testObserver.assertValues(1, 2).assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMerge_thenStream() {
+        val observables = mutableListOf(Observable.just("first", "second"))
+        val observable = observables.merge()
+        observables.add(Observable.just("third", "fourth"))
+        observables.add(Observable.error(Exception("e")))
+        observables.add(Observable.just("fifth"))
+
+        observable.test().assertValues("first", "second", "third", "fourth").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMergeDelayError_thenStream() {
+        val observables = mutableListOf<Observable<String>>(Observable.error(Exception("e1")))
+        val observable = observables.mergeDelayError()
+        observables.add(Observable.just("1", "2"))
+        observables.add(Observable.error(Exception("e2")))
+        observables.add(Observable.just("3"))
+
+        observable.test().assertValues("1", "2", "3").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenCast_thenUniformType() {
+        val observable = Observable.just<Number>(1, 1, 2, 3)
+        observable.cast<Int>().test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenOfType_thenFilter() {
+        val observable = Observable.just(1, "and", 2, "and")
+        observable.ofType<Int>().test().assertValues(1, 2)
+    }
+
+    @Test
+    fun whenFunction_thenCompletable() {
+        var value = 0
+        val completable = { value = 3 }.toCompletable()
+        assertFalse(completable.test().isCancelled)
+        assertEquals(3, value)
+    }
+
+    @Test
+    fun whenHelper_thenMoreIdiomaticKotlin() {
+        val zipWith = Observable.just(1).zipWith(Observable.just(2)) { a, b -> a + b }
+        zipWith.subscribeBy(onNext = { println(it) })
+        val zip = Observables.zip(Observable.just(1), Observable.just(2)) { a, b -> a + b }
+        zip.subscribeBy(onNext = { println(it) })
+        val zipOrig = Observable.zip(Observable.just(1), Observable.just(2), BiFunction<Int, Int, Int> { a, b -> a + b })
+        zipOrig.subscribeBy(onNext = { println(it) })
+    }
+}

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/spek/CalculatorSubjectTest5.kt

@@ -0,0 +1,19 @@
+package com.baeldung.kotlin.spek
+
+import com.baeldung.kotlin.junit5.Calculator
+import org.jetbrains.spek.api.dsl.describe
+import org.jetbrains.spek.api.dsl.it
+import org.jetbrains.spek.subject.SubjectSpek
+import org.junit.jupiter.api.Assertions.assertEquals
+
+class CalculatorSubjectTest5 : SubjectSpek<Calculator>({
+    subject { Calculator() }
+    describe("A calculator") {
+        describe("Addition") {
+            val result = subject.add(3, 5)
+            it("Produces the correct answer") {
+                assertEquals(8, result)
+            }
+        }
+    }
+})

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/spek/CalculatorTest5.kt

@@ -0,0 +1,32 @@
+package com.baeldung.kotlin.spek
+
+import com.baeldung.kotlin.junit5.Calculator
+import org.jetbrains.spek.api.Spek
+import org.jetbrains.spek.api.dsl.describe
+import org.jetbrains.spek.api.dsl.given
+import org.jetbrains.spek.api.dsl.it
+import org.jetbrains.spek.api.dsl.on
+import org.junit.jupiter.api.Assertions.assertEquals
+
+class CalculatorTest5 : Spek({
+    given("A calculator") {
+        val calculator = Calculator()
+        on("Adding 3 and 5") {
+            val result = calculator.add(3, 5)
+            it("Produces 8") {
+                assertEquals(8, result)
+            }
+        }
+    }
+
+    describe("A calculator") {
+        val calculator = Calculator()
+        describe("Addition") {
+            val result = calculator.add(3, 5)
+            it("Produces the correct answer") {
+                assertEquals(8, result)
+            }
+        }
+    }
+
+})

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/spek/DataDrivenTest5.kt

@@ -0,0 +1,21 @@
+package com.baeldung.kotlin.spek
+
+import org.jetbrains.spek.api.Spek
+import org.jetbrains.spek.api.dsl.describe
+import org.jetbrains.spek.api.dsl.it
+import org.junit.jupiter.api.Assertions
+
+class DataDrivenTest5 : Spek({
+    describe("A data driven test") {
+        mapOf(
+                "hello" to "HELLO",
+                "world" to "WORLD"
+        ).forEach { input, expected ->
+            describe("Capitalising $input") {
+                it("Correctly returns $expected") {
+                    Assertions.assertEquals(expected, input.toUpperCase())
+                }
+            }
+        }
+    }
+})

kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/spek/GroupTest5.kt

@@ -0,0 +1,62 @@
+package com.baeldung.kotlin.spek
+
+import org.jetbrains.spek.api.Spek
+import org.jetbrains.spek.api.dsl.describe
+import org.jetbrains.spek.api.dsl.it
+
+class GroupTest5 : Spek({
+    describe("Outer group") {
+        beforeEachTest {
+            System.out.println("BeforeEachTest 0")
+        }
+        beforeGroup {
+            System.out.println("BeforeGroup 0")
+        }
+        afterEachTest {
+            System.out.println("AfterEachTest 0")
+        }
+        afterGroup {
+            System.out.println("AfterGroup 0")
+        }
+        describe("Inner group 1") {
+            beforeEachTest {
+                System.out.println("BeforeEachTest 1")
+            }
+            beforeGroup {
+                System.out.println("BeforeGroup 1")
+            }
+            afterEachTest {
+                System.out.println("AfterEachTest 1")
+            }
+            afterGroup {
+                System.out.println("AfterGroup 1")
+            }
+            it("Test 1") {
+                System.out.println("Test 1")
+            }
+            it("Test 2") {
+                System.out.println("Test 2")
+            }
+        }
+        describe("Inner group 2") {
+            beforeEachTest {
+                System.out.println("BeforeEachTest 2")
+            }
+            beforeGroup {
+                System.out.println("BeforeGroup 2")
+            }
+            afterEachTest {
+                System.out.println("AfterEachTest 2")
+            }
+            afterGroup {
+                System.out.println("AfterGroup 2")
+            }
+            it("Test 3") {
+                System.out.println("Test 3")
+            }
+            it("Test 4") {
+                System.out.println("Test 4")
+            }
+        }
+    }
+})