Add proper unit tests for facade pattern

facade/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>

facade/src/test/java/com/iluwatar/facade/DwarvenGoldmineFacadeTest.java

@@ -0,0 +1,103 @@
+package com.iluwatar.facade;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.PrintStream;
+
+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: 12/9/15 - 9:40 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class DwarvenGoldmineFacadeTest {
+
+  /**
+   * The mocked standard out {@link PrintStream}, required since the actions on the gold mine facade
+   * don't have any influence on any other accessible objects, except for writing to 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 a complete day cycle in the gold mine by executing all three different steps: {@link
+   * DwarvenGoldmineFacade#startNewDay()}, {@link DwarvenGoldmineFacade#digOutGold()} and {@link
+   * DwarvenGoldmineFacade#endDay()}.
+   *
+   * See if the workers are doing what's expected from them on each step.
+   */
+  @Test
+  public void testFullWorkDay() {
+    final DwarvenGoldmineFacade goldMine = new DwarvenGoldmineFacade();
+    goldMine.startNewDay();
+
+    // On the start of a day, all workers should wake up ...
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf gold digger wakes up."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf cart operator wakes up."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarven tunnel digger wakes up."));
+
+    // ... and go to the mine
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf gold digger goes to the mine."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf cart operator goes to the mine."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarven tunnel digger goes to the mine."));
+
+    // No other actions were invoked, so the workers shouldn't have done (printed) anything else
+    verifyNoMoreInteractions(this.stdOutMock);
+
+    // Now do some actual work, start digging gold!
+    goldMine.digOutGold();
+
+    // Since we gave the dig command, every worker should be doing it's job ...
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf gold digger digs for gold."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf cart operator moves gold chunks out of the mine."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarven tunnel digger creates another promising tunnel."));
+
+    // Again, they shouldn't be doing anything else.
+    verifyNoMoreInteractions(this.stdOutMock);
+
+    // Enough gold, lets end the day.
+    goldMine.endDay();
+
+    // Check if the workers go home ...
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf gold digger goes home."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf cart operator goes home."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarven tunnel digger goes home."));
+
+    // ... and go to sleep. We need well rested workers the next day :)
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf gold digger goes to sleep."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarf cart operator goes to sleep."));
+    verify(this.stdOutMock, times(1)).println(eq("Dwarven tunnel digger goes to sleep."));
+
+    // Every worker should be sleeping now, no other actions allowed
+    verifyNoMoreInteractions(this.stdOutMock);
+  }
+
+}