def test_expression_with_string_and_replacements(self):
fit = Fit(model=self.get_model())
fit.expression = 'exp'
a, k, t, tau = fit.model.get_symbols('a', 'k', 't', 'τ')
fit.replacements = (k, 1 / tau)
expression = a * sympy.functions.exp(-t / tau)
eq_(fit.expression, expression)
def test_expression_with_replacements(self):
fit = Fit(model=self.get_model())
fit.replacements = 'tau'
fit.expression = fit.model.expressions['exp']
a, t, tau = fit.model.get_symbols('a', 't', 'τ')
expression = a * sympy.functions.exp(-t / tau)
eq_(fit.expression, expression)
