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fix for it, or if something works on Unix but not on Windows.
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Testing exceptions and errors
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-----------------------------
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It's important to test handling of errors and exceptions. Because this
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code is often not hit in ad-hoc testing it can often have hidden bugs --
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it's particularly common to get NameError because the exception code
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references a variable that has since been renamed.
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.. TODO: Something about how to provoke errors in the right way?
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In general we want to test errors at two levels:
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1. A test in ``test_errors.py`` checking that when the exception object is
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constructed with known parameters it produces an expected string form.
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This guards against mistakes in writing the format string, or in the
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``str`` representations of its parameters. There should be one for
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each exception class.
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2. Tests that when an api is called in a particular situation, it raises
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an error of the expected class. You should typically use
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``assertRaises``, which in the Bazaar test suite returns the exception
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object to allow you to examine its parameters.
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In some cases blackbox tests will also want to check error reporting. But
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it can be difficult to provoke every error through the commandline
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interface, so those tests are only done as needed -- eg in response to a
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particular bug or if the error is reported in an unusual way(?) Blackbox
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tests should mostly be testing how the command-line interface works, so
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should only test errors if there is something particular to the cli in how
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they're displayed or handled.
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407
Essential Domain Classes
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########################
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variable, so some bugs are not detected right away.
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The null revision is the ancestor of all revisions. Its revno is 0, its
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revision-id is ``null:``, and its tree is the empty tree. When referring
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to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
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code sometimes uses ``None`` for the null revision, but this practice is
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734
should be only in the command-line tool.
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Bazaar has online help for various topics through ``bzr help COMMAND`` or
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equivalently ``bzr command -h``. We also have help on command options,
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and on other help topics. (See ``help_topics.py``.)
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As for python docstrings, the first paragraph should be a single-sentence
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synopsis of the command.
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The help for options should be one or more proper sentences, starting with
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a capital letter and finishing with a full stop (period).
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All help messages and documentation should have two spaces between
added
removed
doc/developers/HACKING
