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Testing tools#

Iris has various internal convenience functions and utilities available to support writing tests. Using these makes tests quicker and easier to write, and also consistent with the rest of Iris (which makes it easier to work with the code). Most of these conveniences are accessed through the iris.tests.IrisTest class, from which Iris’ test classes then inherit.


All functions listed on this page are defined within as methods of iris.tests.IrisTest_nometa (which iris.tests.IrisTest inherits from). They can be accessed within a test using self.exampleFunction.

Custom assertions#

iris.tests.IrisTest supports a variety of custom unittest-style assertions, such as assertArrayEqual(), assertArrayAlmostEqual().

Saving results#

Some tests compare the generated output to the expected result contained in a file. Custom assertions for this include assertCMLApproxData() assertCDL() assertCML() and assertTextFile(). See docstrings for more information.


Sometimes code changes alter the results expected from a test containing the above methods. These can be updated by removing the existing result files and then running the file containing the test with a --create-missing command line argument, or setting the IRIS_TEST_CREATE_MISSING environment variable to anything non-zero. This will create the files rather than erroring, allowing you to commit the updated results.

Context managers#

Capturing exceptions and logging#

iris.tests.IrisTest includes several context managers that can be used to make test code tidier and easier to read. These include assertWarnsRegexp() and assertLogs().

Temporary files#

It’s also possible to generate temporary files in a concise fashion with temp_filename().


patch() is a wrapper around unittest.patch that will be automatically cleaned up at the end of the test.

Graphic tests#

As a package capable of generating graphical outputs, Iris has utilities for creating and updating graphical tests - see Adding or Updating Graphics Tests for more information.