diff --git a/observer/pom.xml b/observer/pom.xml
index 681c19571..629c07845 100644
--- a/observer/pom.xml
+++ b/observer/pom.xml
@@ -14,5 +14,10 @@
       <artifactId>junit</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>
diff --git a/observer/src/test/java/com/iluwatar/observer/HobbitsTest.java b/observer/src/test/java/com/iluwatar/observer/HobbitsTest.java
new file mode 100644
index 000000000..3571ced63
--- /dev/null
+++ b/observer/src/test/java/com/iluwatar/observer/HobbitsTest.java
@@ -0,0 +1,37 @@
+package com.iluwatar.observer;
+
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+/**
+ * Date: 12/27/15 - 12:07 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+@RunWith(Parameterized.class)
+public class HobbitsTest extends WeatherObserverTest<Hobbits> {
+
+  @Parameterized.Parameters
+  public static Collection<Object[]> data() {
+    final ArrayList<Object[]> testData = new ArrayList<>();
+    testData.add(new Object[]{WeatherType.SUNNY, "The happy hobbits bade in the warm sun."});
+    testData.add(new Object[]{WeatherType.RAINY, "The hobbits look for cover from the rain."});
+    testData.add(new Object[]{WeatherType.WINDY, "The hobbits hold their hats tightly in the windy weather."});
+    testData.add(new Object[]{WeatherType.COLD, "The hobbits are shivering in the cold weather."});
+    return testData;
+  }
+
+  /**
+   * Create a new test with the given weather and expected response
+   *
+   * @param weather  The weather that should be unleashed on the observer
+   * @param response The expected response from the observer
+   */
+  public HobbitsTest(final WeatherType weather, final String response) {
+    super(weather, response, Hobbits::new);
+  }
+
+}
diff --git a/observer/src/test/java/com/iluwatar/observer/OrcsTest.java b/observer/src/test/java/com/iluwatar/observer/OrcsTest.java
new file mode 100644
index 000000000..a59288ab2
--- /dev/null
+++ b/observer/src/test/java/com/iluwatar/observer/OrcsTest.java
@@ -0,0 +1,37 @@
+package com.iluwatar.observer;
+
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+/**
+ * Date: 12/27/15 - 12:07 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+@RunWith(Parameterized.class)
+public class OrcsTest extends WeatherObserverTest<Orcs> {
+
+  @Parameterized.Parameters
+  public static Collection<Object[]> data() {
+    final ArrayList<Object[]> testData = new ArrayList<>();
+    testData.add(new Object[]{WeatherType.SUNNY, "The sun hurts the orcs' eyes."});
+    testData.add(new Object[]{WeatherType.RAINY, "The orcs are dripping wet."});
+    testData.add(new Object[]{WeatherType.WINDY, "The orc smell almost vanishes in the wind."});
+    testData.add(new Object[]{WeatherType.COLD, "The orcs are freezing cold."});
+    return testData;
+  }
+
+  /**
+   * Create a new test with the given weather and expected response
+   *
+   * @param weather  The weather that should be unleashed on the observer
+   * @param response The expected response from the observer
+   */
+  public OrcsTest(final WeatherType weather, final String response) {
+    super(weather, response, Orcs::new);
+  }
+
+}
diff --git a/observer/src/test/java/com/iluwatar/observer/StdOutTest.java b/observer/src/test/java/com/iluwatar/observer/StdOutTest.java
new file mode 100644
index 000000000..013dd67f7
--- /dev/null
+++ b/observer/src/test/java/com/iluwatar/observer/StdOutTest.java
@@ -0,0 +1,54 @@
+package com.iluwatar.observer;
+
+import org.junit.After;
+import org.junit.Before;
+
+import java.io.PrintStream;
+
+import static org.mockito.Mockito.mock;
+
+/**
+ * Date: 12/27/15 - 12:16 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public abstract class StdOutTest {
+
+  /**
+   * The mocked standard out {@link PrintStream}, required since changes in the weather doesn't has
+   * 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);
+  }
+
+  /**
+   * Get the mocked stdOut {@link PrintStream}
+   *
+   * @return The stdOut print stream mock, renewed before each test
+   */
+  final PrintStream getStdOutMock() {
+    return this.stdOutMock;
+  }
+
+}
diff --git a/observer/src/test/java/com/iluwatar/observer/WeatherObserverTest.java b/observer/src/test/java/com/iluwatar/observer/WeatherObserverTest.java
new file mode 100644
index 000000000..e4d6a4430
--- /dev/null
+++ b/observer/src/test/java/com/iluwatar/observer/WeatherObserverTest.java
@@ -0,0 +1,59 @@
+package com.iluwatar.observer;
+
+import org.junit.Test;
+
+import java.util.function.Supplier;
+
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+/**
+ * Date: 12/27/15 - 11:44 AM
+ *
+ * @author Jeroen Meulemeester
+ */
+public abstract class WeatherObserverTest<O extends WeatherObserver> extends StdOutTest {
+
+  /**
+   * The observer instance factory
+   */
+  private final Supplier<O> factory;
+
+  /**
+   * The weather type currently tested
+   */
+  private final WeatherType weather;
+
+  /**
+   * The expected response from the observer
+   */
+  private final String response;
+
+  /**
+   * Create a new test instance using the given parameters
+   *
+   * @param weather  The weather currently being tested
+   * @param response The expected response from the observer
+   * @param factory  The factory, used to create an instance of the tested observer
+   */
+  WeatherObserverTest(final WeatherType weather, final String response, final Supplier<O> factory) {
+    this.weather = weather;
+    this.response = response;
+    this.factory = factory;
+  }
+
+  /**
+   * Verify if the weather has the expected influence on the observer
+   */
+  @Test
+  public void testObserver() {
+    final O observer = this.factory.get();
+    verifyZeroInteractions(getStdOutMock());
+
+    observer.update(this.weather);
+    verify(getStdOutMock()).println(this.response);
+    verifyNoMoreInteractions(getStdOutMock());
+  }
+
+}
\ No newline at end of file
diff --git a/observer/src/test/java/com/iluwatar/observer/WeatherTest.java b/observer/src/test/java/com/iluwatar/observer/WeatherTest.java
new file mode 100644
index 000000000..a195be526
--- /dev/null
+++ b/observer/src/test/java/com/iluwatar/observer/WeatherTest.java
@@ -0,0 +1,61 @@
+package com.iluwatar.observer;
+
+import org.junit.Test;
+import org.mockito.InOrder;
+
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+/**
+ * Date: 12/27/15 - 11:08 AM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class WeatherTest extends StdOutTest {
+
+  /**
+   * Add a {@link WeatherObserver}, verify if it gets notified of a weather change, remove the
+   * observer again and verify that there are no more notifications.
+   */
+  @Test
+  public void testAddRemoveObserver() {
+    final WeatherObserver observer = mock(WeatherObserver.class);
+
+    final Weather weather = new Weather();
+    weather.addObserver(observer);
+    verifyZeroInteractions(observer);
+
+    weather.timePasses();
+    verify(getStdOutMock()).println("The weather changed to rainy.");
+    verify(observer).update(WeatherType.RAINY);
+
+    weather.removeObserver(observer);
+    weather.timePasses();
+    verify(getStdOutMock()).println("The weather changed to windy.");
+
+    verifyNoMoreInteractions(observer, getStdOutMock());
+  }
+
+  /**
+   * Verify if the weather passes in the order of the {@link WeatherType}s
+   */
+  @Test
+  public void testTimePasses() {
+    final WeatherObserver observer = mock(WeatherObserver.class);
+    final Weather weather = new Weather();
+    weather.addObserver(observer);
+
+    final InOrder inOrder = inOrder(observer, getStdOutMock());
+    final WeatherType[] weatherTypes = WeatherType.values();
+    for (int i = 1; i < 20; i++) {
+      weather.timePasses();
+      inOrder.verify(observer).update(weatherTypes[i % weatherTypes.length]);
+    }
+
+    verifyNoMoreInteractions(observer);
+  }
+
+}
\ No newline at end of file