plainbox.testing_utils.testcases – additional TestCase classes

Implementation of additional TestCase classes that aid in testing.

class plainbox.testing_utils.testcases.TestCaseParameters(names, values)[source]

Bases: object

Class for holding test case parameters

Instances of this class are provided as the .parameters attribute to instances of TestCaseWithParameters during run().

The class supports attribute lookup so tests can be written in convenient form. Having a test case with parameters ‘foo’ and ‘bar’ they can be accessed as self.parameters.foo and self.parameters.bar respectively.

class plainbox.testing_utils.testcases.TestCaseWithParameters(methodName='runTest', parameters=None)[source]

Bases: unittest.case.TestCase

TestCase parametrized by any number of named parameters.

This class can save a lot of typing or creating dummy base classes and other implementation tricks that aim to reduce duplication in code that tests multiple values of a parameter.

For all intents and purposes this is just a standard TestClass instance, what makes it different are the few tricks employed to make it appear as a collection of test cases instead.

Each TestCase created from the test_** methods will be invoked for all the parameter values. Any number of parameters that can be provided. A tuple of values must be provided for each parameter.

In simple cases the developer only needs to provide two class attributes, parameter_names and parameter_values. In more complex cases behavior can be customized by defining two class methods, get_parameter_names() and get_parameter_values(). Note that you _must_ define a non-empty list of parameter values, otherwise this test will behave as if it never existed (analogous how multiplication by zero works).

Note

Technical note for tinkerers and subclass authors. Python unittest framework is pretty annoying to work with or extend. In practice you should always keep the source code (of a particular python version) open to reason about it.

Parametrization is implemented by creating additional instances of TestCaseWithParameters with immutable, bound, parameters. That logic is implemented in run(). The multiplication of TestCase instances happens in _parametrize(). If your sub-class needs to do something special there you might need to override it.

Ideally the unittest framework could allow customizing discovery in a standard way. If that were true then we could instantiate parametrized copies early and then let the normal run() mechanics work. Sadly this is not the case.

Most special python methods also had to be overridden to take account of the new _parameters instance attribute. This includes __str__(), __repr__(), __eq__() and __hash__().

Additional methods unique to unittest framework were implemented to convey the value of the parameter back to the user / developer. Those include id() and countTestCases()

addCleanup(function, *args, **kwargs)

Add a function, with arguments, to be called when the test is completed. Functions added are called on a LIFO basis and are called after tearDown on test failure or success.

Cleanup items are called even if setUp fails (unlike tearDown).

addTypeEqualityFunc(typeobj, function)

Add a type specific assertEqual style function to compare a type.

This method is for use by TestCase subclasses that need to register their own type equality functions to provide nicer error messages.

Args:
typeobj: The data type to call this function on when both values
are of the same type in assertEqual().
function: The callable taking two arguments and an optional
msg= argument that raises self.failureException with a useful error message when the two arguments are not equal.
assertAlmostEqual(first, second, places=None, msg=None, delta=None)

Fail if the two objects are unequal as determined by their difference rounded to the given number of decimal places (default 7) and comparing to zero, or by comparing that the between the two objects is more than the given delta.

Note that decimal places (from zero) are usually not the same as significant digits (measured from the most signficant digit).

If the two objects compare equal then they will automatically compare almost equal.

assertAlmostEquals(*args, **kwargs)
assertCountEqual(first, second, msg=None)

An unordered sequence comparison asserting that the same elements, regardless of order. If the same element occurs more than once, it verifies that the elements occur the same number of times.

self.assertEqual(Counter(list(first)),
Counter(list(second)))
Example:
  • [0, 1, 1] and [1, 0, 1] compare equal.
  • [0, 0, 1] and [0, 1] compare unequal.
assertDictContainsSubset(subset, dictionary, msg=None)

Checks whether dictionary is a superset of subset.

assertDictEqual(d1, d2, msg=None)
assertEqual(first, second, msg=None)

Fail if the two objects are unequal as determined by the ‘==’ operator.

assertEquals(*args, **kwargs)
assertFalse(expr, msg=None)

Check that the expression is false.

assertGreater(a, b, msg=None)

Just like self.assertTrue(a > b), but with a nicer default message.

assertGreaterEqual(a, b, msg=None)

Just like self.assertTrue(a >= b), but with a nicer default message.

assertIn(member, container, msg=None)

Just like self.assertTrue(a in b), but with a nicer default message.

assertIs(expr1, expr2, msg=None)

Just like self.assertTrue(a is b), but with a nicer default message.

assertIsInstance(obj, cls, msg=None)

Same as self.assertTrue(isinstance(obj, cls)), with a nicer default message.

assertIsNone(obj, msg=None)

Same as self.assertTrue(obj is None), with a nicer default message.

assertIsNot(expr1, expr2, msg=None)

Just like self.assertTrue(a is not b), but with a nicer default message.

assertIsNotNone(obj, msg=None)

Included for symmetry with assertIsNone.

assertLess(a, b, msg=None)

Just like self.assertTrue(a < b), but with a nicer default message.

assertLessEqual(a, b, msg=None)

Just like self.assertTrue(a <= b), but with a nicer default message.

assertListEqual(list1, list2, msg=None)

A list-specific equality assertion.

Args:

list1: The first list to compare. list2: The second list to compare. msg: Optional message to use on failure instead of a list of

differences.
assertLogs(logger=None, level=None)

Fail unless a log message of level level or higher is emitted on logger_name or its children. If omitted, level defaults to INFO and logger defaults to the root logger.

This method must be used as a context manager, and will yield a recording object with two attributes: output and records. At the end of the context manager, the output attribute will be a list of the matching formatted log messages and the records attribute will be a list of the corresponding LogRecord objects.

Example:

with self.assertLogs('foo', level='INFO') as cm:
    logging.getLogger('foo').info('first message')
    logging.getLogger('foo.bar').error('second message')
self.assertEqual(cm.output, ['INFO:foo:first message',
                             'ERROR:foo.bar:second message'])
assertMultiLineEqual(first, second, msg=None)

Assert that two multi-line strings are equal.

assertNotAlmostEqual(first, second, places=None, msg=None, delta=None)

Fail if the two objects are equal as determined by their difference rounded to the given number of decimal places (default 7) and comparing to zero, or by comparing that the between the two objects is less than the given delta.

Note that decimal places (from zero) are usually not the same as significant digits (measured from the most signficant digit).

Objects that are equal automatically fail.

assertNotAlmostEquals(*args, **kwargs)
assertNotEqual(first, second, msg=None)

Fail if the two objects are equal as determined by the ‘!=’ operator.

assertNotEquals(*args, **kwargs)
assertNotIn(member, container, msg=None)

Just like self.assertTrue(a not in b), but with a nicer default message.

assertNotIsInstance(obj, cls, msg=None)

Included for symmetry with assertIsInstance.

assertNotRegex(text, unexpected_regex, msg=None)

Fail the test if the text matches the regular expression.

assertNotRegexpMatches(*args, **kwargs)
assertRaises(expected_exception, *args, **kwargs)

Fail unless an exception of class expected_exception is raised by the callable when invoked with specified positional and keyword arguments. If a different type of exception is raised, it will not be caught, and the test case will be deemed to have suffered an error, exactly as for an unexpected exception.

If called with the callable and arguments omitted, will return a context object used like this:

with self.assertRaises(SomeException):
    do_something()

An optional keyword argument ‘msg’ can be provided when assertRaises is used as a context object.

The context manager keeps a reference to the exception as the ‘exception’ attribute. This allows you to inspect the exception after the assertion:

with self.assertRaises(SomeException) as cm:
    do_something()
the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)
assertRaisesRegex(expected_exception, expected_regex, *args, **kwargs)

Asserts that the message in a raised exception matches a regex.

Args:

expected_exception: Exception class expected to be raised. expected_regex: Regex (re pattern object or string) expected

to be found in error message.

args: Function to be called and extra positional args. kwargs: Extra kwargs. msg: Optional message used in case of failure. Can only be used

when assertRaisesRegex is used as a context manager.
assertRaisesRegexp(*args, **kwargs)
assertRegex(text, expected_regex, msg=None)

Fail the test unless the text matches the regular expression.

assertRegexpMatches(*args, **kwargs)
assertSequenceEqual(seq1, seq2, msg=None, seq_type=None)

An equality assertion for ordered sequences (like lists and tuples).

For the purposes of this function, a valid ordered sequence type is one which can be indexed, has a length, and has an equality operator.

Args:

seq1: The first sequence to compare. seq2: The second sequence to compare. seq_type: The expected datatype of the sequences, or None if no

datatype should be enforced.
msg: Optional message to use on failure instead of a list of
differences.
assertSetEqual(set1, set2, msg=None)

A set-specific equality assertion.

Args:

set1: The first set to compare. set2: The second set to compare. msg: Optional message to use on failure instead of a list of

differences.

assertSetEqual uses ducktyping to support different types of sets, and is optimized for sets specifically (parameters must support a difference method).

assertTrue(expr, msg=None)

Check that the expression is true.

assertTupleEqual(tuple1, tuple2, msg=None)

A tuple-specific equality assertion.

Args:

tuple1: The first tuple to compare. tuple2: The second tuple to compare. msg: Optional message to use on failure instead of a list of

differences.
assertWarns(expected_warning, *args, **kwargs)

Fail unless a warning of class warnClass is triggered by the callable when invoked with specified positional and keyword arguments. If a different type of warning is triggered, it will not be handled: depending on the other warning filtering rules in effect, it might be silenced, printed out, or raised as an exception.

If called with the callable and arguments omitted, will return a context object used like this:

with self.assertWarns(SomeWarning):
    do_something()

An optional keyword argument ‘msg’ can be provided when assertWarns is used as a context object.

The context manager keeps a reference to the first matching warning as the ‘warning’ attribute; similarly, the ‘filename’ and ‘lineno’ attributes give you information about the line of Python code from which the warning was triggered. This allows you to inspect the warning after the assertion:

with self.assertWarns(SomeWarning) as cm:
    do_something()
the_warning = cm.warning
self.assertEqual(the_warning.some_attribute, 147)
assertWarnsRegex(expected_warning, expected_regex, *args, **kwargs)

Asserts that the message in a triggered warning matches a regexp. Basic functioning is similar to assertWarns() with the addition that only warnings whose messages also match the regular expression are considered successful matches.

Args:

expected_warning: Warning class expected to be triggered. expected_regex: Regex (re pattern object or string) expected

to be found in error message.

args: Function to be called and extra positional args. kwargs: Extra kwargs. msg: Optional message used in case of failure. Can only be used

when assertWarnsRegex is used as a context manager.
assert_(*args, **kwargs)
countTestCases()[source]

Overridden method of unittest.TestCase()

Behaves different depending on whether it is called on the original instance or the parametrized instance. The original instance behaves like a TestSuite, returning the number of parameter values.

Each parametrized instance (created with _parametrize()) returns 1

debug()

Run the test without collecting errors in a TestResult

defaultTestResult()
doCleanups()

Execute all cleanup functions. Normally called for you after tearDown.

fail(msg=None)

Fail immediately, with the given message.

failIf(*args, **kwargs)
failIfAlmostEqual(*args, **kwargs)
failIfEqual(*args, **kwargs)
failUnless(*args, **kwargs)
failUnlessAlmostEqual(*args, **kwargs)
failUnlessEqual(*args, **kwargs)
failUnlessRaises(*args, **kwargs)
failureException

alias of AssertionError

classmethod get_parameter_names()[source]

Return a tuple of parameters that affect this test case.

classmethod get_parameter_values()[source]

Return a tuple of tuple of values that should be mapped to subsequent attributes named, as returned by get_parameter_names()

id()[source]

Overridden version of TestCase.id()

This is an internal implementation detail of TestCase, it is used in certain places instead of __str__(). It behaves very similar to what __str__() does, except that it displays the class name differently

longMessage = True
maxDiff = 640
parameter_names = ()
parameter_values = ()
parameters

Return the value of parameters that specialize this test case

Normal instances always return None here, the special, parametrized, instance that is constructed once for each parameter value during run() (where testing actually happens), returns the real value.

run(result=None)[source]

Overridden version of TestCase.run()

Creates additional instances of the class being tested, one for each value returned by get_parameter_values() by calling _parametrize().

Each of the parametrized instances is tested normally.

setUp()

Hook method for setting up the test fixture before exercising it.

setUpClass()

Hook method for setting up class fixture before running tests in the class.

shortDescription()

Returns a one-line description of the test, or None if no description has been provided.

The default implementation of this method returns the first line of the specified test method’s docstring.

skipTest(reason)

Skip this test.

subTest(msg=None, **params)

Return a context manager that will return the enclosed block of code in a subtest identified by the optional message and keyword parameters. A failure in the subtest marks the test case as failed but resumes execution at the end of the enclosed block, allowing further test code to be executed.

tearDown()

Hook method for deconstructing the test fixture after testing it.

tearDownClass()

Hook method for deconstructing the class fixture after running all tests in the class.

plainbox.testing_utils.testcases.load_tests(loader, suite, pattern)[source]
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