Added tests for lazy-loading pattern

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();
+  }
+
+}