BAEL-1843 - JUnit4 -> JUnit5 migration guide (#4816)

* Added code for the migration from JUnit 4 to JUnit 5

* Add example for Rule migration support

* Add fix to access modifiers to test methods

* Remove wrong header

* Add junit5-migration module and its code snippets

* Add module configuration to pom

* Remove test classes that were added for the migration from JUnit 4 to JUnit 5 article (moved under correct module)

testing-modules/junit-5/pom.xml

@@ -33,6 +33,12 @@
             <version>${junit.vintage.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-migrationsupport</artifactId>
+            <version>${junit.vintage.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.apache.logging.log4j</groupId>
             <artifactId>log4j-core</artifactId>

testing-modules/junit-5/src/test/java/com/baeldung/AssertionUnitTest.java

@@ -11,14 +11,17 @@ import java.util.Optional;
 import java.util.function.BooleanSupplier;
 
 import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
 /**
  * Unit test that demonstrate the different assertions available within JUnit 4
  */
+@DisplayName("Test case for assertions")
 public class AssertionUnitTest {
 
     @Test
+    @DisplayName("Arrays should be equals")
     public void whenAssertingArraysEquality_thenEqual() {
         char[] expected = {'J', 'u', 'p', 'i', 't', 'e', 'r'};
         char[] actual = "Jupiter".toCharArray();
@@ -27,6 +30,7 @@ public class AssertionUnitTest {
     }
 
     @Test
+    @DisplayName("The area of two polygons should be equal")
     public void whenAssertingEquality_thenEqual() {
         float square = 2 * 2;
         float rectangle = 2 * 2;

testing-modules/junit-5/src/test/java/com/baeldung/NestedUnitTest.java

@@ -10,13 +10,13 @@ import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
 public class NestedUnitTest {
+
     Stack<Object> stack;
-    boolean isRun = false;
 
     @Test
     @DisplayName("is instantiated with new Stack()")
     void isInstantiatedWithNew() {
-        new Stack<Object>();
+        new Stack<>();
     }
 
     @Nested
@@ -25,7 +25,7 @@ public class NestedUnitTest {
 
         @BeforeEach
         void init() {
-            stack = new Stack<Object>();
+            stack = new Stack<>();
         }
 
         @Test

testing-modules/junit-5/src/test/java/com/baeldung/migration/junit5/AssumptionUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.migration.junit5;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assumptions.assumeFalse;
@@ -10,19 +10,19 @@ import org.junit.jupiter.api.Test;
 public class AssumptionUnitTest {
 
     @Test
-    void trueAssumption() {
-        assumeTrue(5 > 1);
+    public void trueAssumption() {
+        assumeTrue(5 > 1, () -> "5 is greater the 1");
         assertEquals(5 + 2, 7);
     }
 
     @Test
-    void falseAssumption() {
-        assumeFalse(5 < 1);
+    public void falseAssumption() {
+        assumeFalse(5 < 1, () -> "5 is less then 1");
         assertEquals(5 + 2, 7);
     }
 
     @Test
-    void assumptionThat() {
+    public void assumptionThat() {
         String someString = "Just a string";
         assumingThat(someString.equals("Just a string"), () -> assertEquals(2 + 2, 4));
     }