Add module JUnit 5 (#182)

* Create new module JUnit 5

* Test multiple implementations using ArgumentsProvider

* Improve description

* Add a untested method

Author: mincong-h

README.md

@@ -27,7 +27,8 @@ Jetty | Jetty Server.
 JGit | Basic usages of [JGit][jgit].
 JMH | Java Microbenchmark Harness (JMH).
 JSON | JSON conversion libraries in Java.
-JUnit | JUnit testing framework.
+JUnit 4 | JUnit 4 testing framework.
+JUnit 5 | JUnit 5 testing framework.
 Logback | [Logback](http://logback.qos.ch/) logging framework.
 Maven | Basic functionality of Maven.
 Mongo | The MongoDB database

junit5/pom.xml

@@ -0,0 +1,37 @@
+<?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">
+    <parent>
+        <artifactId>java-examples-parent</artifactId>
+        <groupId>io.mincong</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>java-examples-junit5</artifactId>
+    <name>Java Examples - JUnit 5</name>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

junit5/src/main/java/io/mincong/junit5/ChatBot.java

@@ -0,0 +1,5 @@
+package io.mincong.junit5;
+
+public interface ChatBot {
+  String sayHello(String username);
+}

junit5/src/main/java/io/mincong/junit5/StringConcatenationChatBot.java

@@ -0,0 +1,19 @@
+package io.mincong.junit5;
+
+public class StringConcatenationChatBot implements ChatBot {
+
+  @Override
+  public String sayHello(String username) {
+    return "Hello, " + username;
+  }
+
+  /**
+   * In IntelliJ IDEA, run ChatBotTest with coverage and observe the test coverage here. You can see
+   * that this test is not tested. One advantage of using parameterized testing is that it can
+   * increase the test coverage easily with difference scenarios.
+   */
+  @SuppressWarnings("unused")
+  public String sayNo(String username) {
+    return "No, " + username;
+  }
+}

junit5/src/main/java/io/mincong/junit5/StringFormatChatBot.java

@@ -0,0 +1,8 @@
+package io.mincong.junit5;
+
+public class StringFormatChatBot implements ChatBot {
+  @Override
+  public String sayHello(String username) {
+    return String.format("Hello, %s", username);
+  }
+}

junit5/src/test/java/io/mincong/junit5/ChatBotTest.java

@@ -0,0 +1,39 @@
+package io.mincong.junit5;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+class ChatBotTest {
+  /**
+   * Use annotation {@link ParameterizedTest} to test multiple implementation of {@link ChatBot}. It
+   * ensures that all implementations respect the specification of the interface and returns the
+   * expected results regardless the internal implementation.
+   *
+   * @param bot the chat bot to test
+   */
+  @ParameterizedTest
+  @ArgumentsSource(ChatBotProvider.class)
+  void sayHello(ChatBot bot) {
+    assertThat(bot.sayHello("Foo")).isEqualTo("Hello, Foo");
+    assertThat(bot.sayHello("Bar")).isEqualTo("Hello, Bar");
+  }
+
+  public static class ChatBotProvider implements ArgumentsProvider {
+
+    /**
+     * This method creates multiple chat bot instances using different implementations and returns
+     * them as a stream of arguments for the parameterized test.
+     */
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+      return Stream.of(new StringFormatChatBot(), new StringConcatenationChatBot())
+          .map(Arguments::of);
+    }
+  }
+}

junit5/src/test/java/io/mincong/junit5/MathTest.java

@@ -0,0 +1,18 @@
+package io.mincong.junit5;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class MathTest {
+  @ParameterizedTest
+  @CsvSource({
+    "1,  2, 2",
+    "1, -1, 1",
+    "1,  1, 1",
+  })
+  void testMax(int a, int b, int max) {
+    assertThat(Math.max(a, b)).isEqualTo(max);
+  }
+}

pom.xml

@@ -61,6 +61,7 @@
     <module>jetty</module>
     <module>protobuf</module>
     <module>reliability</module>
+    <module>junit5</module>
   </modules>
 
   <dependencyManagement>