def test_parse_raises_error_on_invalid_expression():
"""
Test that attempting to parse an invalid expression allows a ``CalcError``
to propagate correctly.
"""
input_text = "+1"
calc = Calc(text=input_text)
with pytest.raises(CalcError):
calc.parse()
def test_parse_sets_eof():
"""
Test that successfully parsing an arithmetic expression sets the
``current_token`` attribute of a :class:`Calc` to EOF.
"""
input_text = "1+1"
calc = Calc(text=input_text)
calc.parse()
assert calc.current_token.type == EOF
def test_calc_raises_error_on_invalid_tokens():
"""
Test that invalid tokens cause a ``CalcError`` and that the exception stack
trace contains useful information.
"""
input_text = "lumberjack" # Now with 100% more Monty Python references.
calc = Calc(text=input_text)
with pytest.raises(CalcError) as err:
calc.parse()
assert "Invalid token at position 0" in str(err.value)
def test_calc_raises_error_on_unexepected_syntax():
"""
Test that unexpected syntax causes a ``CalcError`` and that the exception
stack trace contains useful information.
"""
input_text = "+"
calc = Calc(text=input_text)
with pytest.raises(CalcError) as err:
calc.parse()
assert "Expected INTEGER at position 1, found PLUS" in str(err.value)
def main():
"""
The main entry point into the ``calc`` program.
This function takes input from the user, attempts to parse it, and either
returns the result or shows a stack trace to make it easier to identify the
root cause of the error.
Args:
None
Returns:
None
"""
while True:
# Attempt to get user input.
try:
text = input('calc> ')
except EOFError: # Allow the user to use ctrl+d to exit the calculator.
break
if not text:
continue
calc = Calc(text)
try:
result = calc.parse()
except CalcError:
traceback.print_exc() # Show a stack trace on errors.
else:
print(result)
def test_parse_supports_addition():
"""Test that a :class:`Calc` can correctly parse the addition operation."""
# Note: This function name was briefly duplicated and therefore didn't run.
input_text = "1+1"
calc = Calc(text=input_text)
assert calc.parse() == 2
