Utilities for writing tests: sandbox directories, mock external programs, graphical doc-tests for cairo surfaces.
The tl.testing distribution
This package provides various utilities that can be used when writing tests.
Sandboxes of directories and files
When testing code that modifies directories and files, it is useful to be able to create and inspect a sample tree of directories and files easily. The tl.testing.fs module provides support for creating a tree from a textual description, listing it in the same format and clean up after itself.
In a doc test, these facilities might be used like this to create and list a directory, a file and a symbolic link:
>>> from tl.testing.fs import new_sandbox, ls >>> new_sandbox("""\ ... d foo ... f foo/bar asdf ... l baz -> foo/bar ... """)
>>> ls() l baz -> foo/bar d foo f foo/bar asdf
See the file fs.txt found with the source code for further advice, including how to set up and tear down tests using file-system sandboxes.
Installing callable scripts
Some functionality one might want to test makes use of external programs such as a pager or a text editor. The tl.testing.script module provides utilities that install simple mock scripts in places where the code to be tested will find them. They take a string of Python code and create a wrapper script that sets the Python path to match that of the test and runs the code.
This is how such a mock script might be used in a doc test:
>>> from tl.testing.script import install >>> script_path = install("print 'A simple script.'") >>> print open(script_path).read() #!... <BLANKLINE> import sys sys.path[:] = [...] <BLANKLINE> print 'A simple script.'
>>> import subprocess >>> sub = subprocess.Popen(script_path, shell=True, stdout=subprocess.PIPE) >>> stdout, stderr = sub.communicate() >>> print stdout A simple script.
See the file script.txt found with the source code for further possibilities how to install and access mock scripts as well as how to tear down tests using mock scripts.
Doc-testing the graphical content of cairo surfaces
While it is straight-forward to compare the content of two cairo surfaces in Python code, handling graphics is beyond doc tests. However, the manuel package can be used to extract more general test cases from a text document while allowing to mix them with doc tests in a natural way.
The tl.testing.cairo module provides a test suite factory that uses manuel to execute graphical tests formulated as restructured-text figures. The caption of such a figure is supposed to be a literal Python expression whose value is a cairo surface, and its image is used as the test expectation.
This is how a surface might be compared to an expected image in a doc test:
>>> import cairo >>> from pkg_resources import resource_filename >>> image = resource_filename( ... 'tl.testing', 'testimages/correct.png') .. figure:: tl/testing/testimages/correct.png ``cairo.ImageSurface.create_from_png(image)``
See the file cairo.txt found with the source code for further advice and documentation of the possible test output.
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