Add proper unit tests for decorator pattern

decorator/pom.xml

@@ -14,5 +14,9 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+    </dependency>
   </dependencies>
 </project>

decorator/src/test/java/com/iluwatar/decorator/SmartTrollTest.java

@@ -0,0 +1,38 @@
+package com.iluwatar.decorator;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/7/15 - 7:47 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class SmartTrollTest {
+
+  @Test
+  public void testSmartTroll() throws Exception {
+    // Create a normal troll first, but make sure we can spy on it later on.
+    final Hostile simpleTroll = spy(new Troll());
+
+    // Now we want to decorate the troll to make it smarter ...
+    final Hostile smartTroll = new SmartTroll(simpleTroll);
+    assertEquals(30, smartTroll.getAttackPower());
+    verify(simpleTroll, times(1)).getAttackPower();
+
+    // Check if the smart troll actions are delegated to the decorated troll
+    smartTroll.attack();
+    verify(simpleTroll, times(1)).attack();
+
+    smartTroll.fleeBattle();
+    verify(simpleTroll, times(1)).fleeBattle();
+    verifyNoMoreInteractions(simpleTroll);
+
+  }
+
+}

decorator/src/test/java/com/iluwatar/decorator/TrollTest.java

@@ -0,0 +1,66 @@
+package com.iluwatar.decorator;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.FileDescriptor;
+import java.io.FileOutputStream;
+import java.io.PrintStream;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.internal.verification.VerificationModeFactory.times;
+
+/**
+ * Date: 12/7/15 - 7:26 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class TrollTest {
+
+  /**
+   * The mocked standard out stream, required since the actions don't have any influence on other
+   * objects, except for writing to the std-out using {@link System#out}
+   */
+  private final PrintStream stdOutMock = mock(PrintStream.class);
+
+  /**
+   * Keep the original std-out so it can be restored after the test
+   */
+  private final PrintStream stdOutOrig = System.out;
+
+  /**
+   * Inject the mocked std-out {@link PrintStream} into the {@link System} class before each test
+   */
+  @Before
+  public void setUp() {
+    System.setOut(this.stdOutMock);
+  }
+
+  /**
+   * Removed the mocked std-out {@link PrintStream} again from the {@link System} class
+   */
+  @After
+  public void tearDown() {
+    System.setOut(this.stdOutOrig);
+  }
+
+  @Test
+  public void testTrollActions() throws Exception {
+    final Troll troll = new Troll();
+    assertEquals(10, troll.getAttackPower());
+
+    troll.attack();
+    verify(this.stdOutMock, times(1)).println(eq("The troll swings at you with a club!"));
+
+    troll.fleeBattle();
+    verify(this.stdOutMock, times(1)).println(eq("The troll shrieks in horror and runs away!"));
+
+    verifyNoMoreInteractions(this.stdOutMock);
+  }
+
+}