Unit Testing

Unit testing means testing components of a program in isolation from each other to make sure every part works on its own before using it with others. Extensive testing helps avoid new updates causing unexpected side effects as well as alleviates general code rot (a more comprehensive wikipedia article on unit testing can be found here).

A typical unit test sets calls some function or method with a given input, looks at the result and makes sure that this result looks as expected. Rather than having lots of stand-alone test programs, Evennia makes use of a central test runner. This is a program that gathers all available tests all over the Evennia source code (called test suites) and runs them all in one go. Errors and tracebacks are reported.

By default Evennia only tests itself. But you can also add your own tests to your game code and have Evennia run those for you.

Running the Evennia test suite

To run the full Evennia test suite, go to your game folder and issue the command

evennia test evennia

This will run all the evennia tests using the default settings. You could also run only a subset of all tests by specifying a subpackage of the library:

evennia test evennia.commands.default

A temporary database will be instantiated to manage the tests. If everything works out you will see how many tests were run and how long it took. If something went wrong you will get error messages. If you contribute to Evennia, this is a useful sanity check to see you haven’t introduced an unexpected bug.

Running tests with custom settings file

If you have implemented your own tests for your game (see below) you can run them from your game dir with

evennia test .

The period (.) means to run all tests found in the current directory and all subdirectories. You could also specify, say, typeclasses or world if you wanted to just run tests in those subdirs.

Those tests will all be run using the default settings. To run the tests with your own settings file you must use the --settings option:

evennia --settings settings.py test .

The --settings option of Evennia takes a file name in the mygame/server/conf folder. It is normally used to swap settings files for testing and development. In combination with test, it forces Evennia to use this settings file over the default one.

Writing new tests

Evennia’s test suite makes use of Django unit test system, which in turn relies on Python’s unittest module.

If you want to help out writing unittests for Evennia, take a look at Evennia’s coveralls.io page. There you see which modules have any form of test coverage and which does not.

To make the test runner find the tests, they must be put in a module named test*.py (so test.py, tests.py etc). Such a test module will be found wherever it is in the package. It can be a good idea to look at some of Evennia’s tests.py modules to see how they look.

Inside a testing file, a unittest.TestCase class is used to test a single aspect or component in various ways. Each test case contains one ore more test methods - these define the actual tests to run. You can name the test methods anything you want as long as the name starts with “test_”. Your TestCase class can also have a method setUp(). This is run before each test, setting up and storing whatever preparations the test methods need. Conversely, a tearDown() method can optionally do cleanup after each test.

To test the results, you use special methods of the TestCase class. Many of those start with “assert”, such as assertEqual or assertTrue.

Example of a TestCase class:

import unittest

# the function we want to test
from mypath import myfunc

class TestObj(unittest.TestCase):
   "This tests a function myfunc."

   def test_return_value(self):
       "test method. Makes sure return value is as expected."
       expected_return = "This is me being nice."
       actual_return = myfunc()
       # test
       self.assertEqual(expected_return, actual_return)
   def test_alternative_call(self):
       "test method. Calls with a keyword argument."
       expected_return = "This is me being baaaad."
       actual_return = myfunc(bad=True)
       # test
       self.assertEqual(expected_return, actual_return)

You might also want to read the documentation for the unittest module.

Using the EvenniaTest class

Evennia offers a custom TestCase, the evennia.utils.test_resources.EvenniaTest class. This class initiates a range of useful properties on themselves for testing Evennia systems. Examples are .player and .session representing a mock connected Player and its Session and .char1 and char2 representing Characters complete with a location in the test database. These are all useful when testing Evennia system requiring any of the default Evennia typeclasses as inputs. See the full definition of the EvenniaTest class in evennia/utils/test_resources.py.

# in a test module

from evennia.utils.test_resources import EvenniaTest

class TestObject(EvenniaTest):
    def test_object_search(self):
        # char1 and char2 are both created in room1
        self.assertEqual(self.char1.search(self.char2.key), self.char2)
        self.assertEqual(self.char1.search(self.char1.location.key), char1.location)
        # ...

Testing in-game Commands

In-game Commands are a special case. Tests for the default commands are put in evennia/commands/default/tests.py. This uses a custom CommandTest class that inherits from evennia.utils.test_resources.EvenniaTest described above. CommandTest supplies extra convenience functions for executing commands and check that their return values (calls of msg() returns expected values. It uses Characters and Sessions generated on the EvenniaTest class to call each class).

Each command tested should have its own TestCase class. Inherit this class from the CommandTest class in the same module to get access to the command-specific utilities mentioned.

from evennia.commands.default.tests import CommandTest
from evennia.commands.default import general
class TestSet(CommandTest):
    "tests the look command by simple call"
    def test_mycmd(self):
        self.call(general.CmdLook(), "here", "Room\nroom_desc")

Unit testing contribs with custom models

A special case is if you were to create a contribution to go to the evennia/contrib folder that uses its own database models. The problem with this is that Evennia (and Django) will only recognize models in settings.INSTALLED_APPS. If a user wants to use your contrib, they will be required to add your models to their settings file. But since contribs are optional you cannot add the model to Evennia’s central settings_default.py file - this would always create your optional models regardless of if the user wants them. But at the same time a contribution is a part of the Evennia distribution and its unit tests should be run with all other Evennia tests using evennia test evennia.

The way to do this is to only temporarily add your models to the INSTALLED_APPS directory when the test runs. here is an example of how to do it.

Note that this solution, derived from this stackexchange answer is currently untested! Please report your findings.
# a file contrib/mycontrib/tests.py

from django.conf import settings
import django
from evennia.utils.test_resources import EvenniaTest

OLD_DEFAULT_SETTINGS = settings.INSTALLED_APPS
DEFAULT_SETTINGS = dict(
    INSTALLED_APPS=(
        'contrib.mycontrib.tests',
        ),
    DATABASES={
        "default": {
            "ENGINE": "django.db.backends.sqlite3"
            }
        },
    SILENCED_SYSTEM_CHECKS=["1_7.W001"],
    )

class TestMyModel(EvenniaTest):
    def setUp(self):

        if not settings.configured:
           settings.configure(**DEFAULT_SETTINGS)
        django.setup()

        from django.core.management import call_command
        from django.db.models import loading
        loading.cache.loaded = False
        call_command('syncdb', verbosity=0)

    def tearDown(self):
        settings.configure(**OLD_DEFAULT_SETTINGS)
        django.setup()

        from django.core.management import call_command
        from django.db.models import loading
        loading.cache.loaded = False
        call_command('syncdb', verbosity=0)

    # test cases below ...

    def test_case(self):
        # test case here

A note on adding new tests

Having an extensive tests suite is very important for avoiding code degradation as Evennia is developed. Only a small fraction of the Evennia codebase is covered by test suites at this point. Writing new tests is not hard, it’s more a matter of finding the time to do so. So adding new tests is really an area where everyone can contribute, also with only limited Python skills.

Testing for Game development (mini-tutorial)

Unit testing can be of paramount importance to game developers. When starting with a new game, it is recommended to look into unit testing as soon as possible; an already huge game is much harder to write tests for. The benefits of testing a game aren’t different from the ones regarding library testing. For example it is easy to introduce bugs that affect previously working code. Testing is there to ensure your project behaves the way it should and continue to do so.

If you have never used unit testing (with Python or another language), you might want to check the official Python documentation about unit testing, particularly the first section dedicated to a basic example.

Basic testing using Evennia

Evennia’s test runner can be used to launch tests in your game directory (let’s call it ‘mygame’). Evennia’s test runner does a few useful things beyond the normal Python unittest module:

  • It creates and sets up an empty database, with some useful objects (players, characters and rooms, among others).
  • It provides simple ways to test commands, which can be somewhat tricky at times, if not tested properly.

Therefore, you should use the command-line to execute the test runner, while specifying your own game directories (not the one containing evennia). Go to your game directory (referred as ‘mygame’ in this section) and execute the test runner:

evennia --settings settings.py test commands

This command will execute Evennia’s test runner using your own settings file. It will set up a dummy database of your choice and look into the ‘commands’ package defined in your game directory (mygame/commands in this example) to find tests. The test module’s name should begin with ‘test’ and contain one or more TestCase. A full example can be found below.

A simple example

In your game directory, go to commands and create a new file tests.py inside (it could be named anything starting with test). We will start by making a test that has nothing to do with Commands, just to show how unit testing works:

# mygame/commands/tests.py

import unittest

class TestString(unittest.TestCase):

    """Unittest for strings (just a basic example)."""

    def test_upper(self):
        """Test the upper() str method."""
        self.assertEqual('foo'.upper(), 'FOO')

This example, inspired from the Python documentation, is used to test the ‘upper()’ method of the ‘str’ class. Not very useful, but it should give you a basic idea of how tests are used.

Let’s execute that test to see if it works.

> evennia --settings settings.py test commands

TESTING: Using specified settings file 'server.conf.settings'.

(Obs: Evennia's full test suite may not pass if the settings are very
different from the default. Use 'test .' as arguments to run only tests
on the game dir.)

Creating test database for alias 'default'...
.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK
Destroying test database for alias 'default'...

We specified the commands package to the evennia test command since that’s where we put out test file. In this case we could just as well just said . to search all of mygame for testing files. If we have a lot of tests it may be useful to test only a single set at a time though. We get an information text telling us we are using our custom settings file (instead of Evennia’s default file) and then the test runs. The test passes! Change the “FOO” string to something else in the test to see how it looks when it fails.

Testing commands

This section will test the proper execution of the ‘abilities’ command, as described in the First Steps Coding page. Follow this tutorial to create the ‘abilities’ command, we will need it to test it.

Testing commands in Evennia is a bit more complex than the simple testing example we have seen. Luckily, Evennia supplies a special test class to do just that … we just need to inherit from it and use it properly. This class is called ‘CommandTest’ and is defined in the ‘evennia.commands.default.tests’ package. To create a test for our ‘abilities’ command, we just need to create a class that inherits from ‘CommandTest’ and add methods.

We could create a new test file for this but for now we just append to the tests.py file we already have in commands from before.

# bottom of mygame/commands/tests.py

from evennia.commands.default.tests import CommandTest

from commands.command import CmdAbilities
from typeclasses.characters import Character

class TestAbilities(CommandTest):

    character_typeclass = Character

    def test_simple(self):
        self.call(CmdAbilities(), "", "STR: 5, AGI: 4, MAG: 2")
  • Line 1-4: we do some importing. ‘CommandTest’ is going to be our base class for our test, so we need it. We also import our command (‘CmdAbilities’ in this case). Finally we import the ‘Character’ typeclass. We need it, since ‘CommandTest’ doesn’t use ‘Character’, but ‘DefaultCharacter’, which means the character calling the command won’t have the abilities we have written in the ‘Character’ typeclass.
  • Line 6-8: that’s the body of our test. Here, a single command is tested in an entire class. Default commands are usually grouped by category in a single class. There is no rule, as long as you know where you put your tests. Note that we set the ‘character_typeclass’ class attribute to Character. As explained above, if you didn’t do that, the system would create a ‘DefaultCharacter’ object, not a ‘Character’. You can try to remove line 4 and 8 to see what happens when running the test.
  • Line 10-11: our unique testing method. Note its name: it should begin by ‘test_’. Apart from that, the method is quite simple: it’s an instance method (so it takes the ‘self’ argument) but no other arguments is needed. The line 11 uses the ‘call’ method, which is defined in ‘CommandTest’. It’s a useful method that compares a command against an expected result. It would be like comparing two strings with ‘assertEqual’, but the ‘call’ method does more things, including testing the command in a realistic way (calling its hooks in the right order, so you don’t have to worry about that).

Our line 11 could be understood as: test the ‘abilities’ command (first parameter), with no argument (second parameter), and check that the character using it receives his/her abilities (third parameter).

Let’s run our new test:

> evennia test unit
[...]
Creating test database for alias 'default'...
..
----------------------------------------------------------------------
Ran 2 tests in 0.156s

OK
Destroying test database for alias 'default'...

Two tests were executed, since we have kept ‘TestString’ from last time. In case of failure, you will get much more information to help you fix the bug.