#34657: Testing assertions `assertContains` and `assertInHTML` should output the
haystack on failure
-------------------------------------+-------------------------------------
Reporter: Thibaud | Owner: nobody
Colas |
Type: New | Status: new
feature |
Component: Testing | Version:
framework | Keywords: testcases, unit
Severity: Normal | tests, HTML, assertions, testing
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
If I use the vanilal Python `assertIn` or `assertRegex`, when the
assertion fails, it’s very simple to assess what went wrong from the test
error only:
{{{
self.assertIn("<b>hey</b>", "<p>Howdy!</p>")
AssertionError: '<b>hey</b>' not found in '<p>Howdy!</p>'
}}}
With Django’s `assertContains` and `assertInHTML`, this gets much harder:
{{{
self.assertInHTML("<b>hey</b>", "<p>Howdy!</p>")
File "/Users/thibaudcolas/Dev/django/html-testing-with-
django/.venv/lib/python3.11/site-packages/django/test/testcases.py", line
1076, in assertInHTML
self.assertTrue(
AssertionError: False is not true : Couldn't find '<b>
hey
</b>' in response
}}}
and:
{{{
self.assertContains(res, "<b>hey</b>")
File "/Users/thibaudcolas/Dev/django/html-testing-with-
django/.venv/lib/python3.11/site-packages/django/test/testcases.py", line
660, in assertContains
self.assertTrue(
AssertionError: False is not true : Couldn't find '<b>hey</b>' in response
}}}
---
In both cases, Django doesn’t display the haystack – so I have to waste a
lot of time going back to my HTML templates to check what they might be
outputting / or potentially load the same scenario in a browser / or
manually add `print` statements to my test cases. This is all very time-
consuming. Instead, it’d be much better if the haystack was just present.
Additionally for `assertInHTML` – it’s annoying that `needle` as displayed
in the failure message is the parser’s output, which is therefore broken
up over multiple lines. It’d be much nicer if the example above resulted
in `AssertionError: False is not true : Couldn't find '<b>hey</b>' in
response`.
---
Test suite I used to compare output for reference:
https://github.com/thibaudcolas/html-testing-with-
django/blob/39c82c410cce4bea71ac54be27be67057f4d8dd8/testing_tests/tests.py#L5
--
Ticket URL: <https://code.djangoproject.com/ticket/34657>
Django <https://code.djangoproject.com/>
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