package com.atlassian.vcache.internal.core.metrics;
   
   import com.atlassian.vcache.internal.RequestContext;
   import com.atlassian.vcache.internal.RequestMetrics;
   import org.junit.Before;
   import org.junit.Test;
   import org.junit.runner.RunWith;
   import org.mockito.Mock;
   import org.mockito.runners.MockitoJUnitRunner;
  
  import java.util.function.Predicate;
  import java.util.function.Supplier;
  
  import static org.hamcrest.CoreMatchers.instanceOf;
  import static org.junit.Assert.assertThat;
  import static org.mockito.Matchers.any;
  import static org.mockito.Mockito.when;
  
  @RunWith(MockitoJUnitRunner.class)
  public class SamplingMetricsCollectorTest {
  
      private SamplingMetricsCollector collector;
  
      @Mock
      private RequestContext requestContext;
  
      @Mock
      private Predicate<RequestContext> collectMetrics;
  
      @Before
      public void setUp() throws Exception {
          collector = new SamplingMetricsCollector(() -> requestContext, collectMetrics);
  
          // Always call the supplier
          when(requestContext.computeIfAbsent(any(), any())).thenAnswer(invocationOnMock ->
                  ((Supplier<RequestMetrics>)invocationOnMock.getArguments()[1]).get());
      }
  
      @Test
      public void shouldReturnEmptyMetricsIfNotCollecting() throws Exception {
          when(collectMetrics.test(requestContext)).thenReturn(false);
          assertThat(collector.obtainMetrics(requestContext), instanceOf(EmptyRequestMetrics.class));
      }
  
      @Test
      public void shouldReturnRealMetricsIfCollecting() throws Exception {
          when(collectMetrics.test(requestContext)).thenReturn(true);
          assertThat(collector.obtainMetrics(requestContext), instanceOf(DefaultRequestMetrics.class));
      }
  }