bdd-coder 1.2.1.dev0

Gherkin language in class-based tests - test suite blueprinting

BDD Coder

A package devoted to agile implementation of class-based behavior tests. It consists of:

• coder package able to
  • make a tester package - test suite - blueprint - see example/tests - from user story specifications in YAML files - see example/specs,
  • patch such tester package with new YAML specifications - see example/new_specs and example/new_tests
• tester package employed to run such blueprint tests, which also has the ability to export their docs as YAML specifications

Test with tox - see tox.ini.

See mastermind for an application.

Story

This package was born as a study of Behavior Driven Development; and from the wish of having a handy implementation of Gherkin language in class-based tests, to be employed so that development cycles start with coding a behavior test suite containing the scenario specifications in test case method __doc__s - as bdd_coder.tester achieves.

In conjunction with bdd_coder.coder, development cycles start with:

1. A set of YAML specifications is agreed and crafted
2. From these, a test suite is automatically created or patched
3. New test step methods are crafted to efficiently achieve 100% behavior coverage

User Story (feature) specifications

Each test suite (tester package) has a structure

├─ __init__.py
├─ aliases.py
├─ base.py
└─ test_stories.py

corresponding to a specifications directory

├─ aliases.yml
└─ features/
   ├─ some-story.yml
   ├─ another-story.yml
   ├─ ...
   └─ this-story.yml

A story YAML file (the ones under features/) corresponds to a test case class declared into test_stories.py, consisting mainly of scenario declarations:

Title: <Story title>  # --> class __name__

Story: |-  # free text --> class __doc__
  As a <user group>
  I want <feature>
  In order to/so that <goal>

Scenarios:
  Scenario name:  # --> scenario __doc__
    - Step "1" with "A" gives `x` and `y`
      # ...
    - Last step with "B" gives `result`
  # ...

# Extra class atributes - ignored in patching
Extra name:
  <yaml-attribute-coded-with-str(yaml.load)>
...

So only the keys Title, Story, Scenarios are reserved.

Scenario names are unique if bdd_coder.tester.decorators.Steps takes validate=True (the default), which also validates class hierarchy.

Step declarations

• Start with a whole word - normally 'Given', 'When', or 'Then' - that is ignored by the tester (only order matters)
• May contain:
  • Input *args sequence of values in double-quotes - passed to the step method
  • Output variable name sequence using backticks - if non-empty, the method should return the output values as a tuple, which are collected by the bdd_coder.tester.decorators.Steps decorator instance, by name into its outputs map of sequences
• May refer to a scenario name, either belonging to the same class (story), or to an inherited class

Aliases

Declared as

Alias sentence:  # --> method to call
  - Step sentence  # from scenario __doc__s
  - Another step sentence
  # ...
# ...

corresponding to aliases.py:

MAP = {
    'step_sentence': 'alias_sentence',
    'another_step_sentence': 'alias_sentence',
    # ...
}

Tester

The core of each test suite consists of the following required class declarations in its base.py module:

from test.case.module import MyTestCase

from bdd_coder.tester import decorators
from bdd_coder.tester import tester

from . import aliases

steps = decorators.Steps(aliases.MAP, logs_path='example/tests/bdd_runs.log')
scenario = decorators.Scenario(steps)


@steps
class BddTester(tester.BddTester):
    """
    The decorated BddTester subclass of this suite - manages scenario runs
    """


class BaseTestCase(tester.BaseTestCase, MyTestCase):
    """
    The base test case of this suite - manages test runs
    """

Then, story test cases are declared in test_stories.py, with

from . import base
from bdd_coder.tester import decorators

as

class StoryTitle(BddTesterSubclass, AnotherBddTesterSubclass, ...[, base.BaseTestCase]):

with scenario declarations

  @base.scenario
  def [test_]scenario_name(self):
      """
      Step "1" with "A" gives `x` and `y`
      ...
      Last step with "B" gives `result`
      """

that will run according to their __doc__s, and the necessary step method definitions.

Test run logging

Implemented behavior test step runs are logged by bdd_coder.tester as

________________________________________________________________________________
1 ✅ NewGame.even_boards:
  1.1 - 2020-12-26 13:53:59.291959 ✅ i_request_a_new_game_with_an_even_number_of_boards [] ↦ ('Even Game',)
  1.2 - 2020-12-26 13:53:59.292028 ✅ a_game_is_created_with_boards_of__guesses ['12'] ↦ ()
2 ✅ ClearBoard.test_start_board:
  2.1 - 2020-12-26 13:53:59.292238 ✅ even_boards [] ↦ ()
  2.2 - 2020-12-26 13:53:59.292316 ✅ i_request_a_clear_board_in_my_new_game [] ↦ ('Board',)
  2.3 - 2020-12-26 13:53:59.292374 ✅ board__is_added_to_the_game [] ↦ ()
3 ❌ NewGame.test_odd_boards:
  3.1 - 2020-12-26 13:54:01.053963 ❌ i_request_a_new_game_with_an_odd_number_of_boards [] ↦ Traceback (most recent call last):
  File "/usr/lib/python3.6/unittest/mock.py", line 939, in __call__
    return _mock_self._mock_call(*args, **kwargs)
  File "/usr/lib/python3.6/unittest/mock.py", line 995, in _mock_call
    raise effect
AssertionError: FAKE

Scenario runs {
    "1✅": "even_boards",
    "2✅": "test_start_board"
    "3❌": "test_odd_boards"
}
Pending []
All scenarios ran ▌ 2 ✅ ▌ 1 ❌

into the logs_path passed to bdd_coder.tester.decorators.Steps.

Commands

Check if pending scenarios

It may happen that all steps - and so all tests - that ran succeeded, but some scenarios were not reached. Run bdd-pending-scenarios after pytest to treat this as an error (recommended)

Some scenarios did not run! Check the logs in [...]

usage: bdd-pending-scenarios [-h] logs_path

positional arguments:
  logs_path   str. Path to BDD run logs file

Export test suite docs as YAML

usage: bdd-make-yaml-specs [-h] [--overwrite] test_module specs_path

positional arguments:
  test_module      str. Passed to `importlib.import_module`
  specs_path       str. Will try to write the YAML files in here

keyword arguments:
  --overwrite, -o

Additionally, validates code against generated specifications.

Coder commands

Make a test suite blueprint

usage: bdd-blueprint [-h] [--base-class BASE_CLASS]
                     [--specs-path SPECS_PATH] [--tests-path TESTS_PATH]
                     [--test-module-name TEST_MODULE_NAME] [--overwrite]

keyword arguments:
  --base-class BASE_CLASS, -b BASE_CLASS
                        str. Default: unittest.TestCase
  --specs-path SPECS_PATH, -s SPECS_PATH
                        str. Default: behaviour/specs. Directory containing the YAML specs
  --tests-path TESTS_PATH, -t TESTS_PATH
                        str. Default: next to specs
  --test-module-name TEST_MODULE_NAME, -tm TEST_MODULE_NAME
                        str. Default: stories. Name for test_<name>.py
  --overwrite, -o

The following:

bdd-coder$ bdd-blueprint -s example/specs -t example/tests --overwrite

will rewrite example/tests (with no changes if example/specs is unmodified), and run pytest on the blueprint yielding the output, like

============================= test session starts ==============================
platform [...]
collecting ... collected 2 items

example/tests/test_stories.py::ClearBoard::test_odd_boards PASSED        [ 50%]
example/tests/test_stories.py::ClearBoard::test_start_board PASSED       [100%]

=========================== 2 passed in 0.04 seconds ===========================

Patch a test suite with new specifications

Use this command in order to update a tester package with new YAML specifications. It removes scenario declarations only; it changes the scenario set, which may imply a new test class hierarchy with new stories and scenarios; it adds the necessary step methods, and new aliases (if any).

usage: bdd-patch [-h] test_module [specs_path]

positional arguments:
  test_module  str. Passed to `importlib.import_module`
  specs_path   str. Directory to take new specs from. Default: specs/ next to test package

The following:

bdd-coder$ bdd-patch example.tests.test_stories example/new_specs

will turn example/tests into example/new_tests, and run pytest on the suite yielding something like

============================= test session starts ==============================
platform [...]
collecting ... collected 3 items

example/tests/test_stories.py::NewGame::test_even_boards PASSED          [ 33%]
example/tests/test_stories.py::NewGame::test_funny_boards PASSED         [ 66%]
example/tests/test_stories.py::NewGame::test_more_boards PASSED          [100%]

=========================== 3 passed in 0.04 seconds ===========================

and a log

________________________________________________________________________________
1 ✅ NewGame.new_player_joins:
  1.1 - 2019-04-01 00:30:50.164042 ✅ a_user_signs_in [] ↦ ()
  1.2 - 2019-04-01 00:30:50.164059 ✅ a_new_player_is_added [] ↦ ()
2 ✅ NewGame.test_even_boards:
  2.1 - 2019-04-01 00:30:50.164178 ✅ new_player_joins [] ↦ ()
  2.2 - 2019-04-01 00:30:50.164188 ✅ i_request_a_new_game_with_an_even_number_of_boards [] ↦ ('game',)
  2.3 - 2019-04-01 00:30:50.164193 ✅ a_game_is_created_with_boards_of__guesses ['12'] ↦ ()
3 ✅ NewGame.new_player_joins:
  3.1 - 2019-04-01 00:30:50.165339 ✅ a_user_signs_in [] ↦ ()
  3.2 - 2019-04-01 00:30:50.165348 ✅ a_new_player_is_added [] ↦ ()
4 ✅ NewGame.test_funny_boards:
  4.1 - 2019-04-01 00:30:50.165422 ✅ new_player_joins [] ↦ ()
  4.2 - 2019-04-01 00:30:50.165429 ✅ class_hierarchy_has_changed [] ↦ ()
5 ✅ NewGame.new_player_joins:
  5.1 - 2019-04-01 00:30:50.166458 ✅ a_user_signs_in [] ↦ ()
  5.2 - 2019-04-01 00:30:50.166466 ✅ a_new_player_is_added [] ↦ ()
6 ✅ NewGame.test_more_boards:
  6.1 - 2019-04-01 00:30:50.166535 ✅ new_player_joins [] ↦ ()
  6.2 - 2019-04-01 00:30:50.166541 ✅ user_is_welcome [] ↦ ()
Scenario runs {
    "1✅-3✅-5✅": "new_player_joins",
    "2✅": "test_even_boards",
    "4✅": "test_funny_boards",
    "6✅": "test_more_boards"
}
Pending []
All scenarios ran ▌ 6 ✅