bdd-coder 2.1.1.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

Although this package is intended to be used with pytest, until version 2.0.0 the base test case class for all test suits bdd_coder.tester.tester.BaseTestCase was a unittest.TestCase subclass. From version 2.0.0 unittest.TestCase is no longer supported, so that pytest's setup and teardown functions - see pytest-xunit_setup - should be implemented instead. See pytest-unittest on the benefits of dropping unittest.TestCase.

See mastermind for an example testing a Django REST Framework API.

Test this package with tox - see tox.ini.

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 ✅ TestClearBoard.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. Base test case class
  --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::TestClearBoard::test_odd_boards PASSED    [ 50%]
example/tests/test_stories.py::TestClearBoard::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::TestNewGame::test_even_boards PASSED      [ 33%]
example/tests/test_stories.py::TestNewGame::test_funny_boards PASSED     [ 66%]
example/tests/test_stories.py::TestNewGame::test_more_boards PASSED      [100%]

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

and a log

________________________________________________________________________________
1 ✅ TestNewGame.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 ✅ TestNewGame.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 ✅ TestNewGame.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 ✅ TestNewGame.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 ✅ TestNewGame.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 ✅ TestNewGame.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 ✅