core/src/test/java/io/grpc/ManagedChannelProviderTest.java

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package io.grpc;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertSame;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

import java.util.ServiceConfigurationError;

/** Unit tests for {@link ManagedChannelProvider}. */
@RunWith(JUnit4.class)
public class ManagedChannelProviderTest {
  private final String serviceFile = "META-INF/services/io.grpc.ManagedChannelProvider";

  @Test(expected = ManagedChannelProvider.ProviderNotFoundException.class)
  public void noProvider() {
    ManagedChannelProvider.provider();
  }

  @Test
  public void multipleProvider() {
    ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
        "io/grpc/ManagedChannelProviderTest-multipleProvider.txt");
    assertSame(Available7Provider.class, ManagedChannelProvider.load(cl).getClass());
  }

  @Test
  public void unavailableProvider() {
    ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
        "io/grpc/ManagedChannelProviderTest-unavailableProvider.txt");
    assertNull(ManagedChannelProvider.load(cl));
  }

  @Test
  public void getCandidatesViaHardCoded_usesProvidedClassLoader() {
    final RuntimeException toThrow = new RuntimeException();
    try {
      ManagedChannelProvider.getCandidatesViaHardCoded(new ClassLoader() {
        @Override
        public Class<?> loadClass(String name) {
          throw toThrow;
        }
      });
      fail("Expected exception");
    } catch (RuntimeException ex) {
      assertSame(toThrow, ex);
    }
  }

  @Test
  public void getCandidatesViaHardCoded_ignoresMissingClasses() {
    Iterable<ManagedChannelProvider> i =
        ManagedChannelProvider.getCandidatesViaHardCoded(new ClassLoader() {
          @Override
          public Class<?> loadClass(String name) throws ClassNotFoundException {
            throw new ClassNotFoundException();
          }
        });
    assertFalse("Iterator should be empty", i.iterator().hasNext());
  }

  @Test
  public void create_throwsErrorOnMisconfiguration() throws Exception {
    class PrivateClass {}

    try {
      ManagedChannelProvider.create(PrivateClass.class);
      fail("Expected exception");
    } catch (ServiceConfigurationError e) {
      assertTrue("Expected ClassCastException cause: " + e.getCause(),
          e.getCause() instanceof ClassCastException);
    }
  }

  private static class BaseProvider extends ManagedChannelProvider {
    private final boolean isAvailable;
    private final int priority;

    public BaseProvider(boolean isAvailable, int priority) {
      this.isAvailable = isAvailable;
      this.priority = priority;
    }

    @Override
    protected boolean isAvailable() {
      return isAvailable;
    }

    @Override
    protected int priority() {
      return priority;
    }

    @Override
    protected ManagedChannelBuilder<?> builderForAddress(String host, int port) {
      throw new UnsupportedOperationException();
    }

    @Override
    protected ManagedChannelBuilder<?> builderForTarget(String target) {
      throw new UnsupportedOperationException();
    }
  }

  public static class Available0Provider extends BaseProvider {
    public Available0Provider() {
      super(true, 0);
    }
  }

  public static class Available5Provider extends BaseProvider {
    public Available5Provider() {
      super(true, 5);
    }
  }

  public static class Available7Provider extends BaseProvider {
    public Available7Provider() {
      super(true, 7);
    }
  }

  public static class UnavailableProvider extends BaseProvider {
    public UnavailableProvider() {
      super(false, 10);
    }

    @Override
    protected int priority() {
      throw new RuntimeException("purposefully broken");
    }
  }
}