95 lines
3.1 KiB
Plaintext
95 lines
3.1 KiB
Plaintext
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pytest_monkeypatch plugin
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=========================
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safely patch object attributes, dicts and environment variables.
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.. contents::
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:local:
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Usage
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----------------
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Use the `monkeypatch funcarg`_ to tweak your global test environment
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for running a particular test. You can safely set/del an attribute,
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dictionary item or environment variable by respective methods
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on the monkeypatch funcarg. If you want e.g. to set an ENV1 variable
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and have os.path.expanduser return a particular directory, you can
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write it down like this:
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.. sourcecode:: python
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def test_mytest(monkeypatch):
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monkeypatch.setenv('ENV1', 'myval')
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monkeypatch.setattr(os.path, 'expanduser', lambda x: '/tmp/xyz')
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... # your test code that uses those patched values implicitely
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After the test function finished all modifications will be undone,
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because the ``monkeypatch.undo()`` method is registered as a finalizer.
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``monkeypatch.setattr/delattr/delitem/delenv()`` all
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by default raise an Exception if the target does not exist.
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Pass ``raising=False`` if you want to skip this check.
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prepending to PATH or other environment variables
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---------------------------------------------------------
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To prepend a value to an already existing environment parameter:
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.. sourcecode:: python
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def test_mypath_finding(monkeypatch):
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monkeypatch.setenv('PATH', 'x/y', prepend=":")
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# in bash language: export PATH=x/y:$PATH
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calling "undo" finalization explicitely
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-----------------------------------------
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At the end of function execution py.test invokes
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a teardown hook which undoes all monkeypatch changes.
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If you do not want to wait that long you can call
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finalization explicitely::
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monkeypatch.undo()
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This will undo previous changes. This call consumes the
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undo stack. Calling it a second time has no effect unless
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you start monkeypatching after the undo call.
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.. _`monkeypatch blog post`: http://tetamap.wordpress.com/2009/03/03/monkeypatching-in-unit-tests-done-right/
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.. _`monkeypatch funcarg`:
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the 'monkeypatch' test function argument
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----------------------------------------
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The returned ``monkeypatch`` funcarg provides these
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helper methods to modify objects, dictionaries or os.environ::
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monkeypatch.setattr(obj, name, value, raising=True)
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monkeypatch.delattr(obj, name, raising=True)
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monkeypatch.setitem(mapping, name, value)
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monkeypatch.delitem(obj, name, raising=True)
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monkeypatch.setenv(name, value, prepend=False)
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monkeypatch.delenv(name, value, raising=True)
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monkeypatch.syspath_prepend(path)
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All modifications will be undone when the requesting
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test function finished its execution. For the ``del``
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methods the ``raising`` parameter determines if a
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KeyError or AttributeError will be raised if the
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deletion has no target.
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Start improving this plugin in 30 seconds
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=========================================
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1. Download `pytest_monkeypatch.py`_ plugin source code
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2. put it somewhere as ``pytest_monkeypatch.py`` into your import path
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3. a subsequent ``py.test`` run will use your local version
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Checkout customize_, other plugins_ or `get in contact`_.
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.. include:: links.txt
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