def test_contract_filter_inline(n):
    assert -1 <= fulfill(invert)(n) <= 1
def test_no_vacuous_fulfill(f):
    with pytest.raises(InvalidArgument):
        fulfill(f)
from hypothesis import given
from hypothesis.errors import InvalidArgument
from hypothesis.strategies import builds, integers
from hypothesis.extra.dpcontracts import fulfill


def identity(x):
    return x


@require('division is undefined for zero', lambda args: args.n != 0)
def invert(n):
    return 1 / n


@given(builds(fulfill(invert), integers()))
def test_contract_filter_builds(x):
    assert -1 <= x <= 1


@given(integers())
def test_contract_filter_inline(n):
    assert -1 <= fulfill(invert)(n) <= 1


@pytest.mark.parametrize('f', [int, identity, lambda x: None])
def test_no_vacuous_fulfill(f):
    with pytest.raises(InvalidArgument):
        fulfill(f)