Add JUnit 5 examples

junit5/pom.xml

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+<?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>
+
+    <groupId>com.baeldung</groupId>
+    <artifactId>junit5</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <name>junit5</name>
+    <description>Intro to JUnit 5</description>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <java.version>1.8</java.version>
+        <!-- Due to a bug in surefire-junit5-5.0.0-ALPHA we use the latest snapshot instead -->
+        <junit.gen5.version>5.0.0-SNAPSHOT</junit.gen5.version>
+    </properties>
+
+    <repositories>
+        <repository>
+            <id>snapshots-repo</id>
+            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
+            <releases>
+                <enabled>false</enabled>
+            </releases>
+            <snapshots>
+                <!-- Do NOT cache JUnit 5 snapshot JARs. -->
+                <updatePolicy>always</updatePolicy>
+                <enabled>true</enabled>
+            </snapshots>
+        </repository>
+    </repositories>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>snapshots-repo</id>
+            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
+            <releases>
+                <enabled>false</enabled>
+            </releases>
+            <snapshots>
+                <!-- Do NOT cache JUnit 5 snapshot JARs. -->
+                <updatePolicy>always</updatePolicy>
+                <enabled>true</enabled>
+            </snapshots>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.1</version>
+                <configuration>
+                    <source>${java.version}</source>
+                    <target>${java.version}</target>
+                </configuration>
+            </plugin>
+            <plugin>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.19</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.junit</groupId>
+                        <artifactId>surefire-junit5</artifactId>
+                        <version>${junit.gen5.version}</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit</groupId>
+            <artifactId>junit5-api</artifactId>
+            <version>${junit.gen5.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

junit5/src/test/java/com/baeldung/AssumptionTest.java

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+package com.baeldung;
+
+import org.junit.gen5.api.Test;
+
+import static org.junit.gen5.api.Assertions.assertEquals;
+import static org.junit.gen5.api.Assumptions.*;
+
+public class AssumptionTest {
+
+    @Test
+    void trueAssumption() {
+        assumeTrue(5 > 1);
+        assertEquals(5 + 2, 7);
+    }
+
+    @Test
+    void falseAssumption() {
+        assumeFalse(5 < 1);
+        assertEquals(5 + 2, 7);
+    }
+
+    @Test
+    void assumptionThat() {
+        String someString = "Just a string";
+        assumingThat(
+                someString.equals("Just a string"),
+                () -> assertEquals(2 + 2, 4)
+        );
+    }
+}

junit5/src/test/java/com/baeldung/ExceptionTest.java

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+package com.baeldung;
+
+import org.junit.gen5.api.Test;
+
+import static org.junit.gen5.api.Assertions.assertEquals;
+import static org.junit.gen5.api.Assertions.expectThrows;
+
+public class ExceptionTest {
+
+    @Test
+    void shouldThrowException() {
+        Throwable exception = expectThrows(UnsupportedOperationException.class,
+                () -> {
+                    throw new UnsupportedOperationException("Not supported");
+                });
+        assertEquals(exception.getMessage(), "Not supported");
+    }
+}

junit5/src/test/java/com/baeldung/FirstTest.java

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+package com.baeldung;
+
+import org.junit.gen5.api.Disabled;
+import org.junit.gen5.api.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.gen5.api.Assertions.*;
+
+class FirstTest {
+
+    @Test
+    void lambdaExpressions() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3);
+        assertTrue(numbers
+                .stream()
+                .mapToInt(i -> i)
+                .sum() > 5, "Sum should be greater than 5");
+    }
+
+    @Test
+    void groupAssertions() {
+        int[] numbers = {0, 1, 2, 3, 4};
+        assertAll("numbers",
+                () -> assertEquals(numbers[0], 1),
+                () -> assertEquals(numbers[3], 3),
+                () -> assertEquals(numbers[4], 1)
+        );
+    }
+
+    @Test
+    @Disabled
+    void disabledTest() {
+        assertTrue(false);
+    }
+}

junit5/src/test/java/com/baeldung/NestedTest.java

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+package com.baeldung;
+
+import org.junit.gen5.api.*;
+
+import java.util.EmptyStackException;
+import java.util.Stack;
+
+public class NestedTest {
+    Stack<Object> stack;
+    boolean isRun = false;
+
+    @Test
+    @DisplayName("is instantiated with new Stack()")
+    void isInstantiatedWithNew() {
+        new Stack<Object>();
+    }
+
+    @Nested
+    @DisplayName("when new")
+    class WhenNew {
+
+        @BeforeEach
+        void init() {
+            stack = new Stack<Object>();
+        }
+
+        @Test
+        @DisplayName("is empty")
+        void isEmpty() {
+            Assertions.assertTrue(stack.isEmpty());
+        }
+
+        @Test
+        @DisplayName("throws EmptyStackException when popped")
+        void throwsExceptionWhenPopped() {
+            Assertions.expectThrows(EmptyStackException.class, () -> stack.pop());
+        }
+
+        @Test
+        @DisplayName("throws EmptyStackException when peeked")
+        void throwsExceptionWhenPeeked() {
+            Assertions.expectThrows(EmptyStackException.class, () -> stack.peek());
+        }
+
+        @Nested
+        @DisplayName("after pushing an element")
+        class AfterPushing {
+
+            String anElement = "an element";
+
+            @BeforeEach
+            void init() {
+                stack.push(anElement);
+            }
+
+            @Test
+            @DisplayName("it is no longer empty")
+            void isEmpty() {
+                Assertions.assertFalse(stack.isEmpty());
+            }
+
+            @Test
+            @DisplayName("returns the element when popped and is empty")
+            void returnElementWhenPopped() {
+                Assertions.assertEquals(anElement, stack.pop());
+                Assertions.assertTrue(stack.isEmpty());
+            }
+
+            @Test
+            @DisplayName("returns the element when peeked but remains not empty")
+            void returnElementWhenPeeked() {
+                Assertions.assertEquals(anElement, stack.peek());
+                Assertions.assertFalse(stack.isEmpty());
+            }
+        }
+    }
+}

junit5/src/test/java/com/baeldung/TaggedTest.java

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+package com.baeldung;
+
+import org.junit.gen5.api.Tag;
+import org.junit.gen5.api.Test;
+
+import static org.junit.gen5.api.Assertions.assertEquals;
+
+@Tag("Test case")
+public class TaggedTest {
+
+    @Test
+    @Tag("Method")
+    void testMethod() {
+        assertEquals(2 + 2, 4);
+    }
+}