def test_not_violated_if_variable_equal(self):
# Arrange
expected_value = 1
variable = Variable('1', Domain([expected_value]))
constraint = EqualConstraint(variable, expected_value)
assignment = Assignment()
assignment.set(variable.name, expected_value)
# Act
result = constraint.is_violated(assignment)
# Assert
self.assertFalse(result)
def test_unset_removes_assignment(self):
# Arrange
variable_name = 'A'
assignment = Assignment()
assignment.set(variable_name, 10)
# Act
assignment.unset(variable_name)
# Assert
self.assertEqual(0, assignment.count())
self.assertFalse(assignment.is_set(variable_name))
self.assertIsNone(assignment.get(variable_name))
def test_set_adds_assignment(self):
# Arrange
assignment = Assignment()
variable_name = 'A'
variable_value = 10
# Act
assignment.set(variable_name, variable_value)
# Assert
self.assertEqual(1, assignment.count())
self.assertTrue(assignment.is_set(variable_name))
self.assertEqual(variable_value, assignment.get(variable_name))
def test_not_violated_if_all_variables_different(self):
# Arrange
assignment = Assignment()
variables = []
for i in range(9):
variable = Variable(str(i), Domain(list(range(1, 10))))
variables.append(variable)
assignment.set(variable.name, i + 1)
constraint = AllDiffConstraint(variables)
# Act
result = constraint.is_violated(assignment)
# Assert
self.assertFalse(result)
def test_not_consistent_if_assignment_violates_constraint(self):
# Arrange
variables = [
Variable('1', Domain([1, 2, 3])),
Variable('2', Domain([1, 2]))
]
constraints = [EqualConstraint(variables[0], 2)]
csp = ConstraintSatisfactionProblem(variables, constraints)
assignment = Assignment()
assignment.set(variables[0].name, 3)
# Act
consistent = csp.consistent(assignment)
# Assert
self.assertFalse(consistent)
def test_consistent_for_partial_assignment(self):
# Arrange
variables = [
Variable('1', Domain([1, 2, 3])),
Variable('2', Domain([1, 2]))
]
constraints = [EqualConstraint(variables[0], 2)]
csp = ConstraintSatisfactionProblem(variables, constraints)
assignment = Assignment()
assignment.set(variables[0].name, 2)
# Act
consistent = csp.consistent(assignment)
# Assert
self.assertTrue(consistent)
def test_not_violated_if_some_variables_not_set(self):
# Arrange
assignment = Assignment()
variables = []
for i in range(9):
variable = Variable(str(i), Domain(list(range(1, 10))))
variables.append(variable)
if i < 4:
# Only assign some of the values
assignment.set(variable.name, i + 1)
constraint = AllDiffConstraint(variables)
# Act
result = constraint.is_violated(assignment)
# Assert
self.assertFalse(result)
def test_select_unassigned_variable_returns_valid_variable(self):
# Arrange
variables = [
Variable('1', Domain([1, 2, 3])),
Variable('2', Domain([1, 2]))
]
constraints = [EqualConstraint(variables[0], 2)]
csp = ConstraintSatisfactionProblem(variables, constraints)
assignment = Assignment()
assignment.set(variables[0].name, 2)
# Act
variable = csp.select_unassigned_variable(assignment)
# Assert
self.assertIsNotNone(variable)
self.assertEqual(variables[1].name, variable.name)
def test_violated_if_at_least_one_variable_not_different(self):
# Arrange
assignment = Assignment()
variables = []
for i in range(8):
variable = Variable(str(i), Domain(list(range(1, 10))))
variables.append(variable)
assignment.set(variable.name, i + 1)
non_unique_variable = Variable('8', Domain(list(range(1, 10))))
variables.append(non_unique_variable)
assignment.set(non_unique_variable.name, 1)
constraint = AllDiffConstraint(variables)
# Act
result = constraint.is_violated(assignment)
# Assert
self.assertTrue(result)
def test_select_unassigned_variable_raises_exception_if_variable_not_available(
self):
# Arrange
exception_thrown = False
variables = [Variable('1', Domain([1]))]
constraints = []
csp = ConstraintSatisfactionProblem(variables, constraints)
assignment = Assignment()
assignment.set(variables[0].name, 1)
# Act
try:
csp.select_unassigned_variable(assignment)
except:
exception_thrown = True
# Assert
self.assertTrue(exception_thrown)
