Add unit tests to MapperManager class (#9534)

plugin/datasource/src/test/java/com/alibaba/nacos/plugin/datasource/MapperManagerTest.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 1999-2022 Alibaba Group Holding Ltd.
+ *
+ * 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 com.alibaba.nacos.plugin.datasource;
+
+import com.alibaba.nacos.plugin.datasource.constants.DataSourceConstant;
+import com.alibaba.nacos.plugin.datasource.mapper.AbstractMapper;
+import com.alibaba.nacos.plugin.datasource.mapper.Mapper;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+
+public class MapperManagerTest {
+    
+    @Test
+    public void testInstance() {
+        MapperManager instance = MapperManager.instance();
+        Assert.assertNotNull(instance);
+    }
+    
+    @Test
+    public void testLoadInitial() throws NoSuchFieldException, IllegalAccessException {
+        MapperManager instance = MapperManager.instance();
+        instance.loadInitial();
+        Class<MapperManager> mapperManagerClass = MapperManager.class;
+        Field declaredField = mapperManagerClass.getDeclaredField("MAPPER_SPI_MAP");
+        declaredField.setAccessible(true);
+        Map<String, Map<String, Mapper>> map = (Map<String, Map<String, Mapper>>) declaredField.get(instance);
+        Assert.assertEquals(2, map.size());
+    }
+    
+    @Test
+    public void testJoin() {
+        MapperManager.join(new AbstractMapper() {
+            @Override
+            public String getTableName() {
+                return "test";
+            }
+            
+            @Override
+            public String getDataSource() {
+                return DataSourceConstant.MYSQL;
+            }
+        });
+        MapperManager instance = MapperManager.instance();
+        Mapper mapper = instance.findMapper(DataSourceConstant.MYSQL, "test");
+        Assert.assertNotNull(mapper);
+    }
+    
+    @Test
+    public void testFindMapper() {
+        testJoin();
+        MapperManager instance = MapperManager.instance();
+        Mapper mapper = instance.findMapper(DataSourceConstant.MYSQL, "test");
+        Assert.assertNotNull(mapper);
+    }
+}