How to use the deal.inv function in deal

def test_scheme_contract_is_satisfied_when_setting_arg(scheme):
    @deal.inv(scheme)
    class User:
        name = ''

    user = User()

    user.name = 'Chris'

    with pytest.raises(deal.InvContractError):
        user.name = 123

    try:
        user.name = 123
    except deal.InvContractError as e:
        assert e.args[0] == {'name': ['Not a valid string.']}

def test_instance(self):
        class A:
            x = 2
        PatchedA = deal.inv(lambda obj: obj.x > 0)(A)  # noQA
        a = PatchedA()
        with self.subTest(text='isinstance'):
            self.assertIsInstance(a, PatchedA)
            self.assertIsInstance(a, A)

        PatchedA2 = deal.inv(lambda obj: obj.x > 0)(PatchedA)  # noQA
        a = PatchedA2()
        with self.subTest(text='isinstance'):
            self.assertIsInstance(a, PatchedA)
            self.assertIsInstance(a, PatchedA2)
            self.assertIsInstance(a, A)
        with self.subTest(text='class name'):
            self.assertEqual(a.__class__.__name__.count('Invarianted'), 1)

def test_patched_invariants_instance():
    class A:
        x = 2

    PatchedA = deal.inv(lambda obj: obj.x > 0)(A)  # noQA
    a = PatchedA()
    assert isinstance(a, PatchedA)
    assert isinstance(a, A)

    PatchedA2 = deal.inv(lambda obj: obj.x > 0)(PatchedA)  # noQA
    a = PatchedA2()
    assert isinstance(a, PatchedA)
    assert isinstance(a, PatchedA2)
    assert isinstance(a, A)

    assert a.__class__.__name__.count('Invarianted') == 1

def test_scheme_contract_is_satisfied_within_chain(scheme):
    @deal.inv(lambda user: user.name != 'Oleg')
    @deal.inv(scheme)
    @deal.inv(lambda user: user.name != 'Chris')
    class User:
        name = ''

    user = User()
    user.name = 'Gram'

    user = User()
    with pytest.raises(deal.InvContractError):
        user.name = 'Oleg'

    user = User()
    with pytest.raises(deal.InvContractError):
        user.name = 123

    user = User()

def test_invariant_chain(self):
        @deal.inv(lambda user: user.name != 'Oleg')
        @deal.inv(self.Scheme)
        @deal.inv(lambda user: user.name != 'Chris')
        class User:
            name = ''

        user = User()
        with self.subTest('simple call'):
            user.name = 'Gram'

        user = User()
        with self.subTest('not passed first validation'):
            with pytest.raises(deal.InvContractError):
                user.name = 'Oleg'

        user = User()
        with self.subTest('not passed second validation'):
            with pytest.raises(deal.InvContractError):

def test_instance(self):
        class A:
            x = 2
        PatchedA = deal.inv(lambda obj: obj.x > 0)(A)  # noQA
        a = PatchedA()
        with self.subTest(text='isinstance'):
            self.assertIsInstance(a, PatchedA)
            self.assertIsInstance(a, A)

        PatchedA2 = deal.inv(lambda obj: obj.x > 0)(PatchedA)  # noQA
        a = PatchedA2()
        with self.subTest(text='isinstance'):
            self.assertIsInstance(a, PatchedA)
            self.assertIsInstance(a, PatchedA2)
            self.assertIsInstance(a, A)
        with self.subTest(text='class name'):
            self.assertEqual(a.__class__.__name__.count('Invarianted'), 1)

def test_setattr(self):
        @deal.inv(lambda obj: obj.x > 0)
        class A:
            x = 2

        a = A()
        with self.subTest(text='good'):
            a.x = 4
        with self.subTest(text='error'):
            with pytest.raises(deal.InvContractError):
                a.x = -2

def test_patched_invariants_instance():
    class A:
        x = 2

    PatchedA = deal.inv(lambda obj: obj.x > 0)(A)  # noQA
    a = PatchedA()
    assert isinstance(a, PatchedA)
    assert isinstance(a, A)

    PatchedA2 = deal.inv(lambda obj: obj.x > 0)(PatchedA)  # noQA
    a = PatchedA2()
    assert isinstance(a, PatchedA)
    assert isinstance(a, PatchedA2)
    assert isinstance(a, A)

    assert a.__class__.__name__.count('Invarianted') == 1