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A spec tool to describe your classes

Project description


A PHPSpec-like for Python. For fun only (for now). If you're looking for a real valid PHPSpec-like, you could check flowp (but deprecated). mamba could also interest you, even if it's not exactly what you are searching.


pip install specify


You can check the examples folder.

from specify import ObjectBehavior
from examples.calculator import Calculator

class CalculatorSpec(ObjectBehavior):
    def _let(self):
        self._be_constructed_with('lorem', id=32)

    def it_adds_the_numbers(self):
        self.add(2, 3)._should_be(5)

The command python -m specify examples/spec/ will render a valid TAP output (hopefully).

TAP version 13

ok 1 - CalculatorSpec: it adds the numbers

To have a nice and pretty output, you can then use a TAP formatter like faucet.

  • All specifications must start by it_.

  • All spec files must end by _spec for now.

Builtin matchers

Matcher Details Alias
_should_be check with is _should_return
_should_be_like check with == _should_return_like
_should_not_be check with is not _should_not_return
_should_not_be_like check with != _should_not_return_like
_should_be_an_instance_of check with isinstance _should_return_an_instance_of
_should_have_length check with len(x)

Custom matchers

You can implement a _matchers function in your spec, to add custom matchers.

The key of the matcher is left trimmed by _should_ and the first argument passed to your function is the value itself.

If you return false, the test will fail.

Here is an example:

class CalculatorSpec(ObjectBehavior):
    # ...

    def it_adds_the_numbers(self):
        self.add(2, 3)._should_be_a_number()
        self.add(2, 3)._should_be_greater_than(10)

    def _matchers(self):
        def be_a_number(value, *args):
            return isinstance(value, int)

        def be_greater_than(value, expected_value):
            return value > expected_value

        return {
            'be_a_number': be_a_number,
            'be_greater_than': be_greater_than

Fluent API

All matchers (builtin and custom) are chainable. Example:

self.add(2, 3)._should_be_a_number()._should_be(5)._should_be_greater_than(3)


Thanks to prophepy (did you get the pun with prophecy? Hoho), you can easily mock things in a Prophecy way.


Given this Displayer class:

from .calculator import Calculator

class Displayer:
    def __init__(self, calculator: Calculator):
        self.calculator = calculator

    def display_addition(self, *args) -> str:
        total = str(self.calculator.add(*args))
        args = [str(arg) for arg in args]

        return f"{' + '.join(args)} = {total}"

Here is the spec, mocking the Calculator:

from specify import ObjectBehavior, mock
from examples.calculator import Calculator
from examples.displayer import Displayer

class DisplayerSpec(ObjectBehavior):

    def _let(self, calculator):
        self.__calculator = calculator

    def it_displays_addition(self):
        self.__calculator.add(2, 3)._should_be_called()
        self.__calculator.add(2, 3)._will_return(5)
        self.display_addition(2, 3)._should_be_like('2 + 3 = 5')

Easy peasy.

Internal calls to modules

from specify import mock_internal

# ...

@mock_internal('getcwd', lambda : 'loremipsum', from_module='os')
def it_displays_addition(self):
    # ...
    # getcwd() will return 'loremipsum' and will be go back to default after
    the test


  • Handle attributes and not only methods
  • Improve the way interal calls are mocked
  • Make the tap output a stream as the spec say
  • Improve the shitty way specs are loaded for now (maybe use ast like mamba?)

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