@Test
public void throwsIOExceptionForCircuitBreakerException() throws Exception {

    expect(mockBackend.execute(host, req, ctx))
        .andThrow(new CircuitBreakerException());
    replay(mockBackend);
    try {
        impl.execute(host, req, ctx);
        fail("should have thrown exception");
    } catch (IOException expected) {
    }
    verify(mockBackend);
}