/**
    * 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.hadoop.hbase.metrics;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertNotEquals;
  import static org.mockito.Mockito.mock;
  
  import org.apache.hadoop.hbase.testclassification.SmallTests;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  
  import com.google.common.collect.Lists;
  
  /**
   * Test class for {@link MetricRegistriesLoader}.
   */
  @Category(SmallTests.class)
  public class TestMetricRegistriesLoader {
  
    @Test
    public void testLoadSinleInstance() {
      MetricRegistries loader = mock(MetricRegistries.class);
      MetricRegistries instance = MetricRegistriesLoader.load(Lists.newArrayList(loader));
      assertEquals(loader, instance);
    }
  
    @Test
    public void testLoadMultipleInstances() {
      MetricRegistries loader1 = mock(MetricRegistries.class);
      MetricRegistries loader2 = mock(MetricRegistries.class);
      MetricRegistries loader3 = mock(MetricRegistries.class);
      MetricRegistries instance = MetricRegistriesLoader.load(Lists.newArrayList(loader1, loader2,
          loader3));
  
      // the load() returns the first instance
      assertEquals(loader1, instance);
      assertNotEquals(loader2, instance);
      assertNotEquals(loader3, instance);
    }
  }