Added tests for lazy-loading pattern

lazy-loading/src/test/java/com/iluwatar/lazy/loading/AbstractHolderTest.java

@@ -0,0 +1,41 @@
+package com.iluwatar.lazy.loading;
+
+import org.junit.Test;
+
+import static junit.framework.Assert.assertNotNull;
+import static junit.framework.Assert.assertSame;
+import static junit.framework.TestCase.assertNull;
+
+/**
+ * Date: 12/19/15 - 11:58 AM
+ *
+ * @author Jeroen Meulemeester
+ */
+public abstract class AbstractHolderTest {
+
+  /**
+   * Get the internal state of the holder value
+   *
+   * @return The internal value
+   */
+  abstract Heavy getInternalHeavyValue() throws Exception;
+
+  /**
+   * Request a lazy loaded {@link Heavy} object from the holder.
+   *
+   * @return The lazy loaded {@link Heavy} object
+   */
+  abstract Heavy getHeavy() throws Exception;
+
+  /**
+   * This test shows that the heavy field is not instantiated until the method getHeavy is called
+   */
+  @Test(timeout = 3000)
+  public void testGetHeavy() throws Exception {
+    assertNull(getInternalHeavyValue());
+    assertNotNull(getHeavy());
+    assertNotNull(getInternalHeavyValue());
+    assertSame(getHeavy(), getInternalHeavyValue());
+  }
+
+}