BAEL-7006 Create example code for environment variables article

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesByAbstractionUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class EnvironmentVariablesByAbstractionUnitTest {
+
+    @FunctionalInterface
+    interface GetEnv {
+        String get(String name);
+    }
+
+    static class ReadsEnvironment {
+        private GetEnv getEnv;
+
+        public ReadsEnvironment(GetEnv getEnv) {
+            this.getEnv = getEnv;
+        }
+
+        public String whatOs() {
+            return getEnv.get("OS");
+        }
+    }
+
+    @Test
+    void givenFakeOs_thenCanReadIt() {
+        Map<String, String> fakeEnv = new HashMap<>();
+        fakeEnv.put("OS", "MacDowsNix");
+
+        ReadsEnvironment reader = new ReadsEnvironment(fakeEnv::get);
+        assertThat(reader.whatOs())
+          .isEqualTo("MacDowsNix");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSetByJUnitPioneerUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.Test;
+import org.junitpioneer.jupiter.ClearEnvironmentVariable;
+import org.junitpioneer.jupiter.SetEnvironmentVariable;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SetEnvironmentVariable(key = "pioneer", value = "is pioneering")
+class EnvironmentVariablesSetByJUnitPioneerUnitTest {
+
+    @Test
+    void givenEnvironmentVariableIsSetForClass_thenVariableCanBeRead() {
+        assertThat(System.getenv("pioneer")).isEqualTo("is pioneering");
+    }
+
+    @ClearEnvironmentVariable(key = "pioneer")
+    @Test
+    void givenEnvironmentVariableIsClear_thenItIsNotSet() {
+        assertThat(System.getenv("pioneer")).isNull();
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSetDirectlyUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+import static org.assertj.core.api.Assertions.assertThat;
+
+// This test can only work well in Java 15 and below
+class EnvironmentVariablesSetDirectlyUnitTest {
+    @BeforeAll
+    static void beforeAll() throws Exception {
+        Class<?> classOfMap = System.getenv().getClass();
+        Field field = classOfMap.getDeclaredField("m");
+        field.setAccessible(true);
+        Map<String, String> writeableEnvironmentVariables = (Map<String, String>)field.get(System.getenv());
+
+        writeableEnvironmentVariables.put("baeldung", "has set an environment variable");
+    }
+
+    @Test
+    void givenEnvironmentVariableWasSet_thenCanReadIt() {
+        assertThat(System.getenv("baeldung")).isEqualTo("has set an environment variable");
+    }
+
+    @Test
+    void givenEnvironmentVariableSetBySurefire_thenCanReadIt() {
+        assertThat(System.getenv("SET_BY_SUREFIRE")).isEqualTo("YES");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemLambdaUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.Test;
+
+import static com.github.stefanbirkner.systemlambda.SystemLambda.withEnvironmentVariable;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class EnvironmentVariablesSystemLambdaUnitTest {
+
+    @Test
+    void givenSetEnvironmentVariablesInTest_thenCanBeRead() throws Exception {
+        withEnvironmentVariable("system lambda", "in test")
+          .execute(() -> {
+              assertThat(System.getenv("system lambda")).isEqualTo("in test");
+          });
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemRulesUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.EnvironmentVariables;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EnvironmentVariablesSystemRulesUnitTest {
+    @Rule
+    public EnvironmentVariables environmentVariablesRule = new EnvironmentVariables();
+
+    @Before
+    public void before() {
+        environmentVariablesRule.set("system rules", "works");
+    }
+
+    @Test
+    public void givenEnvironmentVariable_thenCanReadIt() {
+        assertThat(System.getenv("system rules")).isEqualTo("works");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemStubsJUnit4UnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.Rule;
+import org.junit.Test;
+import uk.org.webcompere.systemstubs.rules.EnvironmentVariablesRule;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EnvironmentVariablesSystemStubsJUnit4UnitTest {
+    @Rule
+    public EnvironmentVariablesRule environmentVariablesRule =
+      new EnvironmentVariablesRule("system stubs", "initializes variable");
+
+    @Test
+    public void givenEnvironmentSetUpInObject_thenCanReadIt() {
+        assertThat(System.getenv("system stubs")).isEqualTo("initializes variable");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemStubsJUnit5UnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import uk.org.webcompere.systemstubs.environment.EnvironmentVariables;
+import uk.org.webcompere.systemstubs.jupiter.SystemStub;
+import uk.org.webcompere.systemstubs.jupiter.SystemStubsExtension;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(SystemStubsExtension.class)
+class EnvironmentVariablesSystemStubsJUnit5UnitTest {
+
+    @SystemStub
+    private EnvironmentVariables environmentVariables;
+
+    @BeforeEach
+    void beforeEach() {
+        environmentVariables.set("systemstubs", "creates stub objects");
+    }
+
+    @Test
+    void givenEnvironmentVariableHasBeenSet_thenCanReadIt() {
+        assertThat(System.getenv("systemstubs")).isEqualTo("creates stub objects");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemStubsNoFrameworkClassScopeEnvironmentUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import uk.org.webcompere.systemstubs.environment.EnvironmentVariables;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class EnvironmentVariablesSystemStubsNoFrameworkClassScopeEnvironmentUnitTest {
+    private static EnvironmentVariables environmentVariables = new EnvironmentVariables();
+
+    @BeforeAll
+    static void beforeAll() throws Exception {
+        environmentVariables.set("system stubs", "in test");
+        environmentVariables.setup();
+    }
+
+    @AfterAll
+    static void afterAll() throws Exception {
+        environmentVariables.teardown();
+    }
+
+    @Test
+    void givenSetEnvironmentVariablesBeforeAll_thenCanBeRead() throws Exception {
+        assertThat(System.getenv("system stubs")).isEqualTo("in test");
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemStubsNoFrameworkUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static uk.org.webcompere.systemstubs.SystemStubs.withEnvironmentVariables;
+
+class EnvironmentVariablesSystemStubsNoFrameworkUnitTest {
+
+    @Test
+    void givenSetEnvironmentVariablesInTest_thenCanBeRead() throws Exception {
+        withEnvironmentVariables("system stubs", "in test")
+          .execute(() -> {
+              assertThat(System.getenv("system stubs")).isEqualTo("in test");
+          });
+    }
+}

testing-modules/testing-libraries-2/src/test/java/com/baeldung/environmentvariablesfortest/EnvironmentVariablesSystemStubsTestNGUnitTest.java

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+package com.baeldung.environmentvariablesfortest;
+
+import org.testng.annotations.BeforeClass;
+import org.testng.annotations.Listeners;
+import org.testng.annotations.Test;
+import uk.org.webcompere.systemstubs.environment.EnvironmentVariables;
+import uk.org.webcompere.systemstubs.testng.SystemStub;
+import uk.org.webcompere.systemstubs.testng.SystemStubsListener;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@Listeners(SystemStubsListener.class)
+public class EnvironmentVariablesSystemStubsTestNGUnitTest {
+    @SystemStub
+    private EnvironmentVariables setEnvironment;
+
+    @BeforeClass
+    public void beforeAll() {
+        setEnvironment.set("testng", "has environment variables");
+    }
+
+    @Test
+    public void givenEnvironmentVariableWasSet_thenItCanBeRead() {
+        assertThat(System.getenv("testng"))
+          .isEqualTo("has environment variables");
+    }
+
+}