new utility for updated cached values in a multi-threaded environment.

[utils] / support / general / src / test / java / org / wamblee / cache / ComputedValueTest.java

diff --git a/support/general/src/test/java/org/wamblee/cache/ComputedValueTest.java b/support/general/src/test/java/org/wamblee/cache/ComputedValueTest.java
new file mode 100644 (file)
index 0000000..d13cd41
--- /dev/null
+++ b/support/general/src/test/java/org/wamblee/cache/ComputedValueTest.java
@@ -0,0 +1,131 @@
+/*
+ * Copyright 2005-2010 the original author or authors.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.wamblee.cache;
+
+import static org.mockito.Mockito.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import junit.framework.TestCase;
+
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+import org.wamblee.cache.ComputedValue.Computation;
+
+public class ComputedValueTest extends TestCase {
+
+    private Computation<Integer> computation;
+    private ComputedValue<Integer> guard;
+    
+
+    @Override
+    protected void setUp() throws Exception {
+        computation = mock(Computation.class);
+    }
+
+    public void testComputeOutOfDate() {
+        initGuard();
+    }
+
+    private void initGuard() {
+        guard = new ComputedValue<Integer>(this, computation);
+
+        assertNull(guard.getCached());
+        
+        when(computation.isOutOfDate()).thenReturn(true);
+        when(computation.compute()).thenReturn(10);
+       
+        int value = guard.get();
+        assertEquals(10, value);
+        verify(computation).compute();
+        reset(computation);
+    }
+    
+    public void testGetCached() { 
+        initGuard();
+        assertEquals(10, (int)guard.getCached());
+        verifyNoMoreInteractions(computation);
+    }
+
+    public void testNoComputationWhenNotOutOfDate() {
+        initGuard();
+        when(computation.isOutOfDate()).thenReturn(false);
+        assertEquals(10, (int) guard.get());
+        verify(computation, never()).compute();
+    }
+
+    public void testOnlyOneConcurrentComputation() throws Exception {
+        initGuard();
+        final int computeTime = 500;
+        when(computation.isOutOfDate()).thenReturn(true);
+        when(computation.compute()).thenAnswer(new Answer<Integer>() {
+            @Override
+            public Integer answer(InvocationOnMock aInvocation)
+                throws Throwable {
+                Thread.sleep(computeTime);
+                return 100;
+            }
+        });
+
+        final List<Integer> results = new ArrayList<Integer>();
+
+        Runnable task = new Runnable() {
+            @Override
+            public void run() {
+                int res = guard.get();
+                results.add(res);
+            }
+        };
+
+        // concurrent computation in two threads.
+        Thread t1 = new Thread(task);
+        Thread t2 = new Thread(task);
+        t1.start();
+        Thread.sleep(computeTime / 2);
+        // second task will return old value 10 because first one is still busy.
+        t2.start();
+        t1.join();
+        t2.join();
+        assertEquals(2, results.size());
+        assertEquals(10, (int) results.get(0));
+        assertEquals(100, (int) results.get(1));
+        verify(computation, times(2)).isOutOfDate();
+    }
+
+    public void testExceptionWhileComputing() {
+        initGuard();
+        when(computation.isOutOfDate()).thenReturn(true);
+        when(computation.compute()).thenThrow(new RuntimeException("xx"));
+        try {
+            guard.get();
+            fail();
+        } catch (RuntimeException e) {
+            assertEquals("xx", e.getMessage());
+        }
+    }
+
+    public void testExceptionWhileCheckingOutOfDate() {
+        initGuard();
+        when(computation.isOutOfDate()).thenThrow(new RuntimeException("xx"));
+        try {
+            guard.get();
+            fail();
+        } catch (RuntimeException e) {
+            assertEquals("xx", e.getMessage());
+        }
+    }
+}