'Test basic functionality of FormulaResponse
Specifically, if it can understand equivalence of formulae'

def test_grade(self):

    sample_dict = {'x': ((-10), 10), 'y': ((-10), 10)}
    problem = self.build_problem(sample_dict=sample_dict, num_samples=10, tolerance=0.01, answer='x+2*y')
    input_formula = '2*x    -    x    +    y    +    y'
    self.assert_grade(problem, input_formula, 'correct')
    input_formula = 'x    +    y'
    self.assert_grade(problem, input_formula, 'incorrect')
