def Call_if_with_a_nonnumber_is_an_error(): assert_fails( "Only numbers may be passed to an if, but I was passed " + "'('string', 'x')'", evald, 'if("x", {}, {});')
def assert_prog_fails(program, error, env=None): assert_fails(error, evald, program, env)
def Calling_set_with_nonstring_is_an_error(): assert_fails( "set() takes a string as its first argument, but was: " + "('number', 3.0)", evald, "x = 3; set(x, 4);")