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Context manager for managing a test file (Python recipe) by Brett Cannon
ActiveState Code (http://code.activestate.com/recipes/502278/)

This recipe helps to manage a temporary file used in a test. It returns an open file so as to write the test data, and upon exiting the 'with' statement, makes sure that the created file is deleted.

Python, 12 lines
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from contextlib import contextmanager
import os

@contextmanager
def test_file(path):
    try:
        open_file = open(path, 'w')
        yield open_file
    finally:
        open_file.close()
        if os.path.exists(path):
            os.unlink(path)

unittest.TestCase.setUp/tearDown are not always the right level of granularity for tests. Sometimes what needs to be written to a test file varies widely between tests. It can be convenient to have unique code per test for writing out to a test file.

This context manager is for those situations. Just write to the open file, close it, and then use the file path or open a new file object within the 'with' statement. You are guaranteed that the file will be deleted at the end of your code.