test: Add test case for RunsOldestTaskPolicy #1335 (#1347)

* test: Add test case for RunsOldestTaskPolicy #1335

* make test viewable by codecov #1335

infra/common/src/test/java/cn/hippo4j/common/executor/support/RunsOldestTaskPolicyTest.java

@@ -0,0 +1,100 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 cn.hippo4j.common.executor.support;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@RunWith(MockitoJUnitRunner.class)
+public class RunsOldestTaskPolicyTest {
+
+    private final RunsOldestTaskPolicy runsOldestTaskPolicy = new RunsOldestTaskPolicy();
+
+    @Mock
+    private Runnable runnable;
+
+    @Mock
+    private Runnable runnableInTheQueue;
+
+    @Mock
+    private ThreadPoolExecutor threadPoolExecutor;
+
+    @Mock
+    private BlockingQueue<Runnable> workQueue;
+
+    @Test
+    public void testRejectedExecutionWhenExecutorIsShutDown() {
+        when(threadPoolExecutor.isShutdown()).thenReturn(true);
+
+        runsOldestTaskPolicy.rejectedExecution(runnable, threadPoolExecutor);
+
+        verify(threadPoolExecutor, never()).execute(runnable);
+        verify(runnable, never()).run();
+    }
+
+    @Test
+    public void testRejectedExecutionWhenATaskIsInTheQueueTheExecutorShouldNotExecute() {
+        when(threadPoolExecutor.isShutdown()).thenReturn(false);
+        when(threadPoolExecutor.getQueue()).thenReturn(workQueue);
+        when(workQueue.poll()).thenReturn(runnableInTheQueue);
+        when(workQueue.offer(runnable)).thenReturn(true);
+
+        runsOldestTaskPolicy.rejectedExecution(runnable, threadPoolExecutor);
+
+        verify(runnableInTheQueue).run();
+        verify(threadPoolExecutor, never()).execute(runnable);
+        verify(runnable, never()).run();
+    }
+
+    @Test
+    public void testRejectedExecutionWhenATaskIsInTheQueueTheExecutorShouldExecute() {
+        when(threadPoolExecutor.isShutdown()).thenReturn(false);
+        when(threadPoolExecutor.getQueue()).thenReturn(workQueue);
+        when(workQueue.poll()).thenReturn(runnableInTheQueue);
+        when(workQueue.offer(runnable)).thenReturn(false);
+
+        runsOldestTaskPolicy.rejectedExecution(runnable, threadPoolExecutor);
+
+        verify(runnableInTheQueue).run();
+        verify(threadPoolExecutor).execute(runnable);
+        verify(runnable, never()).run();
+    }
+
+    @Test
+    public void testRejectedExecutionWhenATaskIsInTheQueueAndThePollReturnANullValue() {
+        when(threadPoolExecutor.isShutdown()).thenReturn(false);
+        when(threadPoolExecutor.getQueue()).thenReturn(workQueue);
+        when(workQueue.poll()).thenReturn(null);
+        when(workQueue.offer(runnable)).thenReturn(false);
+
+        runsOldestTaskPolicy.rejectedExecution(runnable, threadPoolExecutor);
+
+        verify(runnableInTheQueue, never()).run();
+        verify(threadPoolExecutor).execute(runnable);
+        verify(runnable, never()).run();
+    }
+}