unittest
It ain't broke, let's fix it!
unittest is actually pretty good
Two reasons for reluctance
Robert Collins <robert.collins@canonical.com>
Caged deathmatch
Time for questions
1. Structure of unittest
2. Extending unittest
3. Good and bad points
4. Caged deathmatch
unittest is actually pretty good
<h2>What is it?</h2>
Help you write tests
Not really it
API for manipulating & running tests
API for manipulating & running arbitrary user code with a narrow, predefined range of results
Three core classes
Three core concepts
"Find arbitrary chunk of user code" class
"Arbitrary chunk of user code" class
"Collect results of user code" class
None of the other classes matter
TestRunner, TestSuite
Ignoring TestLoader
The narrow interface of TestCase
<<list slide>>
*That's* the public interface.
Not assertEqual or setUp or whatever
The less narrow interface of TestResult
<<list slide>>
(circa Python 2.3)
Reporting test activity
How they fit together
test_case.run(test_result)
test_result.addFoo(test_case, foo)
<h2>How (not) to extend unit test</h2>
Some examples
Sharing expensive resources between tests
Twisted
Trial
setUpClass / tearDownClass
My mistake
TestCase.setUpClass, TestCase.tearDownClass
Define attributes, those attributes available to tests in that class.
Bad because:
Test correctness depended on test ordering
Couldn't interleave tests from one class with tests from another.
Breaks implicit contract of unittest
A TestCase instance is a standalone thing
Next example
Zope
zope.testing layers
Similar problem
Test defines magical attribute
Loader finds attribute, constructs tests appropriately
Requires special TestResult object to store state
You cannot construct a test that uses layers and run it
You must use the Zope infrastructure
<h2>How to extend unit test</h2>
testresources
bzr branch lp:testresources
Resource manager objects
Acquire and release resources from these objects
class ResourcedTestCase(TestCase):
Define 'resources' attribute
Customized setUp and tearDown that acquire and release
run() works
OptimizedTestSuite that orders tests
Doesn't affect test results at all
Maintains contract
subunit
bzr branch lp:subunit
Customized test result that allows running tests out of process
Javascript
Perl
C
Cloud
<h2>Checkpoint</h2>
unittest model is right
Not super clear from the code
Interoperable extensions
It ain't broke
<h2>Let's Fix It!</h2>
It's got bugs.
Props to Michael Foord
addCleanup
Some bugs
countTestCases
Loading all tests before running, not removing from memory
Biggest problem...
Culture of interoperability
FIGHT!