testGetDefaultRenderer() {
    const rx1 = registry.getDefaultRenderer(FakeComponentX);
    const rx2 = registry.getDefaultRenderer(FakeComponentX);
    assertTrue(
        'FakeComponentX\'s default renderer must be a FakeRenderer',
        rx1 instanceof FakeRenderer);
    assertNotEquals(
        'Each call to getDefaultRenderer must create a new ' +
            'FakeRenderer',
        rx1, rx2);

    const ry = registry.getDefaultRenderer(FakeComponentY);
    assertTrue(
        'FakeComponentY must inherit its default renderer from ' +
            'its superclass',
        ry instanceof FakeRenderer);

    const rz1 = registry.getDefaultRenderer(FakeComponentZ);
    const rz2 = registry.getDefaultRenderer(FakeComponentZ);
    assertTrue(
        'FakeComponentZ\' default renderer must be a ' +
            'FakeSingletonRenderer',
        rz1 instanceof FakeSingletonRenderer);
    assertEquals(
        'Each call to getDefaultRenderer must return the ' +
            'singleton instance of FakeSingletonRenderer',
        rz1, rz2);

    assertNull(
        'getDefaultRenderer must return null for unknown component',
        registry.getDefaultRenderer(UnknownComponent));
  }
@suppress {checkTypes} suppression added to
                               enable type checking