assertTrue(
          "stream not closed when copying from source with option: " + option,
          !okSink.wasStreamOpened() || okSink.wasStreamClosed());
    }
  }

  public void testClosesOnErrors_whenWriteThrows() {
    TestCharSink failSink = new TestCharSink(WRITE_THROWS);
    assertThrows(IOException.class, () -> new TestCharSource(STRING).copyTo(failSink));
    assertTrue(failSink.wasStreamClosed());
  }