def test_multi_dep_optional():
    @lambda_solid
    def ret_one():
        return 1

    @solid(output_defs=[OutputDefinition(name='skip', is_required=False)])
    def skip(_):
        return
        yield  # pylint: disable=unreachable

    @solid(output_defs=[OutputDefinition(name='skip', is_required=False)])
    def skip_downstream(_, skip_upstream):
        return
        yield  # pylint: disable=unreachable

    @solid
    def collect(_, items):
        return items

    @pipeline
    def test_remaining():
        collect([ret_one(), skip()])

    result = execute_pipeline(test_remaining)
    assert result.success
    assert result.result_for_solid('collect').output_value() == [1]

    @pipeline
    def test_all_skip():
        collect([skip(), skip(), skip()])

    result = execute_pipeline(test_all_skip)
    assert result.success
    assert result.result_for_solid('collect').skipped

    @pipeline
    def test_skipped_upstream():
        collect([ret_one(), skip_downstream(skip())])

    result = execute_pipeline(test_skipped_upstream)
    assert result.success
    assert result.result_for_solid('collect').output_value() == [1]