Add unit test for PipelineJobCenter (#28879)

* 28542-Add-unit-test-for-PipelineJobCenter

* 28542-Add-unit-test-for-PipelineJobCenter

* Made all the changes as mentioned in review comments.

* Formatted the code as per code of conduct and made the changes as mentioned in the review comments.

* Corrected the checkstyle errors

* Updated method name

kernel/data-pipeline/core/src/test/java/org/apache/shardingsphere/data/pipeline/core/job/PipelineJobCenterTest.java

@@ -0,0 +1,81 @@
+/*
+ * 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 org.apache.shardingsphere.data.pipeline.core.job;
+
+import org.apache.shardingsphere.data.pipeline.common.context.PipelineJobItemContext;
+import org.apache.shardingsphere.data.pipeline.common.job.PipelineJob;
+import org.apache.shardingsphere.data.pipeline.core.task.runner.PipelineTasksRunner;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+class PipelineJobCenterTest {
+
+    @Test
+    void assertPipelineJobCenter() {
+        PipelineJob pipelineJob = mock(PipelineJob.class);
+        PipelineJobCenter.addJob("Job1", pipelineJob);
+        assertTrue(PipelineJobCenter.isJobExisting("Job1"));
+        assertFalse(PipelineJobCenter.isJobExisting("Job2"));
+        assertNotNull(PipelineJobCenter.getJob("Job1"));
+        assertEquals(pipelineJob, PipelineJobCenter.getJob("Job1"));
+        assertNull(PipelineJobCenter.getJob("Job2"));
+        PipelineJobCenter.stop("Job1");
+    }
+
+    @Test
+    void assertGetJobItemContext() {
+        PipelineJob pipelineJob = mock(PipelineJob.class);
+        PipelineTasksRunner pipelineTasksRunner = mock(PipelineTasksRunner.class);
+        PipelineJobItemContext pipelineJobItemContext = mock(PipelineJobItemContext.class);
+        when(pipelineJob.getTasksRunner(anyInt())).thenReturn(Optional.of(pipelineTasksRunner));
+        when(pipelineTasksRunner.getJobItemContext()).thenReturn(pipelineJobItemContext);
+        PipelineJobCenter.addJob("Job1", pipelineJob);
+        Optional<PipelineJobItemContext> result = PipelineJobCenter.getJobItemContext("Job1", 1);
+        Optional<PipelineJobItemContext> optionalPipelineJobItemContext = Optional.ofNullable(pipelineJobItemContext);
+        assertTrue(result.isPresent());
+        assertEquals(Optional.empty(), PipelineJobCenter.getJobItemContext("Job2", 1));
+        assertEquals(optionalPipelineJobItemContext, result);
+        PipelineJobCenter.stop("Job1");
+    }
+
+    @Test
+    void assertGetShardingItems() {
+        PipelineJob pipelineJob = mock(PipelineJob.class);
+        PipelineJobCenter.addJob("Job1", pipelineJob);
+        when(pipelineJob.getShardingItems()).thenReturn(Arrays.asList(1, 2, 3));
+        Collection<Integer> shardingItems = pipelineJob.getShardingItems();
+        Assertions.assertFalse(shardingItems.isEmpty());
+        Assertions.assertEquals(Arrays.asList(1, 2, 3), PipelineJobCenter.getShardingItems("Job1"));
+        assertEquals(Collections.EMPTY_LIST, PipelineJobCenter.getShardingItems("Job2"));
+        PipelineJobCenter.stop("Job1");
+    }
+}