def test_givenACallableWhichTakesMoreThanOneParameter_whenMappingOrFiltering_thenExpandTupleToMultipleParameters(
self):
tupleNullable = Nullable((1, 2))
sum = tupleNullable.map(lambda x, y: x + y)
self.assertEqual(3, sum.get())
class NullableTest(unittest.TestCase):
def setUp(self):
self.null = Nullable(None)
self.non_null = Nullable(ITEM)
def test_whenCheckingIsPresent_thenChecksIfItemValueIsNone(self):
self.assertFalse(self.null.isPresent())
self.assertTrue(self.non_null.isPresent())
def test_whenGettingValue_thenReturnStoredItemValueOrThrowException(self):
self.assertEqual(ITEM, self.non_null.get())
with self.assertRaises(EmptyNullableException):
self.null.get()
def test_whenUsingOrElse_thenReturnsDefaultValueForMissingItem(self):
default_value = object()
self.assertEqual(ITEM, self.non_null.orElse(default_value))
self.assertEqual(default_value, self.null.orElse(default_value))
def test_whenUsingOrElseThrow_thenRaiseExceptionForMissingItem(self):
an_exception = Exception
self.assertEqual(ITEM, self.non_null.orElseThrow(an_exception))
with self.assertRaises(an_exception):
self.null.orElseThrow(an_exception)
def test_givenExceptionFactory_whenUsingOrElseThrow_thenInvokeTheCallableToGetTheThrownException(
self):
callable_which_returns_an_exception = MagicMock()
callable_which_returns_an_exception.return_value = Exception()
with self.assertRaises(Exception):
self.null.orElseThrow(callable_which_returns_an_exception)
self.assertTrue(callable_which_returns_an_exception.called)
def test_whenUsingOrElseFetch_thenInvokeTheCallableForMissingValues(self):
default_value = object()
callable = lambda: default_value
self.assertEqual(ITEM, self.non_null.get())
self.assertEqual(default_value, self.null.orElseFetch(callable))
def test_whenFiltering_thenCreateANullableWithFilteredItem(self):
criterion = lambda x: x is ITEM
unsatisfied_criterion = lambda x: False
filtered = self.non_null.filter(criterion)
unsatisfied_filter = self.non_null.filter(unsatisfied_criterion)
self.assertEqual(ITEM, filtered.get())
self.assertFalse(unsatisfied_filter.isPresent())
def test_givenMissingItem_whenFiltering_thenReturnEmptyNullable(self):
criterion = lambda x: False
filtered = self.null.filter(criterion)
self.assertFalse(filtered.isPresent())
def test_whenMapping_thenCreateANullableIfValueIsPresent(self):
mapped_value = object()
mapping_function = lambda x: mapped_value
mapped_null = self.null.map(mapping_function)
mapped_non_null = self.non_null.map(mapping_function)
self.assertTrue(mapped_non_null.isPresent())
self.assertFalse(mapped_null.isPresent())
def test_givenMissingItem_whenMapping_thenCallbackIsNeverInvoked(self):
mapping_function = MagicMock()
self.null.map(mapping_function)
self.assertFalse(mapping_function.called)
def test_whenEvaluatingToBoolean_thenReturnIfItemIsPresent(self):
self.assertTrue(self.non_null)
self.assertFalse(self.null)
def test_whenUsingIfPresent_thenInvokeOnlyWhenItemIsPresent(self):
mock = MagicMock()
callback = lambda x: mock()
self.null.ifPresent(callback)
self.assertFalse(mock.called)
self.non_null.ifPresent(callback)
self.assertTrue(mock.called)
def test_givenACallableWhichTakesMoreThanOneParameter_whenMappingOrFiltering_thenExpandTupleToMultipleParameters(
self):
tupleNullable = Nullable((1, 2))
sum = tupleNullable.map(lambda x, y: x + y)
self.assertEqual(3, sum.get())