content: /*
   * 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.calcite.avatica.metrics;
  
  import org.apache.calcite.avatica.metrics.noop.NoopMetricsSystem;
  import org.apache.calcite.avatica.metrics.noop.NoopMetricsSystemConfiguration;
  
  import org.junit.Test;
  import org.mockito.Mockito;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  import static org.junit.Assert.assertEquals;
  
  /**
   * Test class for {@link MetricsSystemLoader}.
   */
  public class MetricsSystemLoaderTest {
  
    @Test public void testSingleInstance() {
      final List<MetricsSystemFactory> factories =
          Collections.<MetricsSystemFactory>singletonList(new MarkedNoopMetricsSystemFactory());
      MetricsSystemLoader loader = Mockito.mock(MetricsSystemLoader.class);
  
      Mockito.when(loader.getFactories()).thenReturn(factories);
      Mockito.when(loader._load(Mockito.any(MetricsSystemConfiguration.class))).thenCallRealMethod();
  
      // One MetricsSystemFactory should return the MetricsSystem it creates
      MetricsSystem system = loader._load(NoopMetricsSystemConfiguration.getInstance());
      assertEquals(MarkedMetricsSystem.INSTANCE, system);
    }
  
    @Test public void testMultipleInstances() {
      // The type of the factories doesn't matter (we can send duplicates for testing purposes)
      final List<MetricsSystemFactory> factories =
          Arrays.<MetricsSystemFactory>asList(new MarkedNoopMetricsSystemFactory(),
              new MarkedNoopMetricsSystemFactory());
      MetricsSystemLoader loader = Mockito.mock(MetricsSystemLoader.class);
  
      Mockito.when(loader.getFactories()).thenReturn(factories);
      Mockito.when(loader._load(Mockito.any(MetricsSystemConfiguration.class))).thenCallRealMethod();
  
      // We had two factories loaded, therefore we'll fall back to the NoopMetricsSystem
      MetricsSystem system = loader._load(NoopMetricsSystemConfiguration.getInstance());
      assertEquals(NoopMetricsSystem.getInstance(), system);
    }
  
    @Test public void testNoInstances() {
      // The type of the factories doesn't matter (we can send duplicates for testing purposes)
      final List<MetricsSystemFactory> factories = Collections.emptyList();
      MetricsSystemLoader loader = Mockito.mock(MetricsSystemLoader.class);
  
      Mockito.when(loader.getFactories()).thenReturn(factories);
      Mockito.when(loader._load(Mockito.any(MetricsSystemConfiguration.class))).thenCallRealMethod();
  
      // We had no factories loaded, therefore we'll fall back to the NoopMetricsSystem
      MetricsSystem system = loader._load(NoopMetricsSystemConfiguration.getInstance());
      assertEquals(NoopMetricsSystem.getInstance(), system);
    }
  
    /**
     * A test factory implementation which can return a recognized MetricsSystem implementation.
     */
    private static class MarkedNoopMetricsSystemFactory implements MetricsSystemFactory {
      public MarkedMetricsSystem create(MetricsSystemConfiguration<?> config) {
        return MarkedMetricsSystem.INSTANCE;
      }
    }
  
    /**
     * A metrics system implementation that is identifiable for testing.
     */
    private static class MarkedMetricsSystem implements MetricsSystem {
      private static final MarkedMetricsSystem INSTANCE = new MarkedMetricsSystem();
  
      private MarkedMetricsSystem() {}
  
      @Override public Timer getTimer(String name) {
        return null;
      }
  
      @Override public Histogram getHistogram(String name) {
        return null;
      }
  
      @Override public Meter getMeter(String name) {
        return null;
      }
  
      @Override public Counter getCounter(String name) {
        return null;
      }
  
      @Override public <T> void register(String name, Gauge<T> gauge) {}
    }
  }
  
  // End MetricsSystemLoaderTest.java
  