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());
+  }
+
+}

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

@@ -0,0 +1,26 @@
+package com.iluwatar.lazy.loading;
+
+import java.lang.reflect.Field;
+
+/**
+ * Date: 12/19/15 - 12:05 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class HolderNaiveTest extends AbstractHolderTest {
+
+  private final HolderNaive holder = new HolderNaive();
+
+  @Override
+  Heavy getInternalHeavyValue() throws Exception {
+    final Field holderField = HolderNaive.class.getDeclaredField("heavy");
+    holderField.setAccessible(true);
+    return (Heavy) holderField.get(this.holder);
+  }
+
+  @Override
+  Heavy getHeavy() {
+    return holder.getHeavy();
+  }
+
+}

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

@@ -1,45 +1,26 @@
 package com.iluwatar.lazy.loading;
 
-import org.junit.Test;
-
 import java.lang.reflect.Field;
 
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-
 /**
- * Using reflection this test shows that the heavy field is not instantiated until the method
- * getHeavy is called
+ * Date: 12/19/15 - 12:19 PM
  *
- * Created by jones on 11/10/2015.
+ * @author Jeroen Meulemeester
  */
-public class HolderThreadSafeTest {
+public class HolderThreadSafeTest extends AbstractHolderTest {
 
-  @Test
-  public void test() throws IllegalAccessException {
-    HolderThreadSafe hts = new HolderThreadSafe();
+  private final HolderThreadSafe holder = new HolderThreadSafe();
 
-    {
-      // first call is null
-      Field[] ff = HolderThreadSafe.class.getDeclaredFields();
-      for (Field f : ff) {
-        f.setAccessible(true);
-      }
-
-      assertNull(ff[0].get(hts));
-    }
-
-    // now it is lazily loaded
-    hts.getHeavy();
-
-    {
-      // now it is not null - call via reflection so that the test is the same before and after
-      Field[] ff = HolderThreadSafe.class.getDeclaredFields();
-      for (Field f : ff) {
-        f.setAccessible(true);
-      }
-
-      assertNotNull(ff[0].get(hts));
-    }
+  @Override
+  Heavy getInternalHeavyValue() throws Exception {
+    final Field holderField = HolderThreadSafe.class.getDeclaredField("heavy");
+    holderField.setAccessible(true);
+    return (Heavy) holderField.get(this.holder);
   }
-}
+
+  @Override
+  Heavy getHeavy() throws Exception {
+    return this.holder.getHeavy();
+  }
+
+}

lazy-loading/src/test/java/com/iluwatar/lazy/loading/Java8HolderTest.java

@@ -0,0 +1,40 @@
+package com.iluwatar.lazy.loading;
+
+import java.lang.reflect.Field;
+import java.util.function.Supplier;
+
+/**
+ * Date: 12/19/15 - 12:27 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class Java8HolderTest extends AbstractHolderTest {
+
+  private final Java8Holder holder = new Java8Holder();
+
+
+  @Override
+  Heavy getInternalHeavyValue() throws Exception {
+    final Field holderField = Java8Holder.class.getDeclaredField("heavy");
+    holderField.setAccessible(true);
+
+    final Supplier<Heavy> supplier = (Supplier<Heavy>) holderField.get(this.holder);
+    final Class<? extends Supplier> supplierClass = supplier.getClass();
+
+    // This is a little fishy, but I don't know another way to test this:
+    // The lazy holder is at first a lambda, but gets replaced with a new supplier after loading ...
+    if (supplierClass.isLocalClass()) {
+      final Field instanceField = supplierClass.getDeclaredField("heavyInstance");
+      instanceField.setAccessible(true);
+      return (Heavy) instanceField.get(supplier);
+    } else {
+      return null;
+    }
+  }
+
+  @Override
+  Heavy getHeavy() throws Exception {
+    return holder.getHeavy();
+  }
+
+}