Test multiple implementations using ArgumentsProvider

Author: mincong-h

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 +1,9 @@
+package io.mincong.junit5;
+
+public class StringConcatenationChatBot implements ChatBot {
+
+  @Override
+  public String sayHello(String username) {
+    return "Hello, " + 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);
+    }
+  }
+}