CSS tests require a specific naming convention. This is also a good, but not mandatory, style to use for other tests.

File Name

The file name format is test-topic-###.ext where test-topic somewhat describes the test, ### is a zero-filled number used to keep the file names unique, and ext is typically either html or xht.

Test filenames must also be globally unique. There cannot be multiple tests with the same filename, even if they are in different parent directories. For example, having both /css-values-3/foo-001.html and /css-variables-1/foo-001.html would not be allowed. This restriction is in place because some tools that use the CSS tests dump all of the test files into a single directory, which would cause all but one of the tests with the same filename to be clobbered and accidentally skipped.


test-topic is a short identifier that describes the test. The test-topic should avoid conjunctions, articles, and prepositions. It is a file name, not an English phrase: it should be as concise as possible.




### is a zero-filled number used to keep the file names unique when files have the same test-topic name.

Note: The number format is limited to 999 cases. If you go over this number it is recommended that you reevaluate your test-topic name.

For example, in the case of margin-collapsing there are multiple cases so each case could have the same test-topic but different numbers:


There may also be a letter affixed after the number, which can be used to indicate variants of a test.

For example, float-wrap-001l.xht and float-wrap-001r.xht might be left and right variants of a float test.

If tests using both the unsuffixed number and the suffixed number exist, the suffixed tests must be subsets of the unsuffixed test.

For example, if bidi-004 and bidi-004a both exist, bidi-004a must be a subset of bidi-004.

If the unsuffixed test is strictly the union of the suffixed tests, i.e. covers all aspects of the suffixed tests (such that a user agent passing the unsuffixed test will, by design, pass all the suffixed tests), then the unsuffixed test should be marked with the combo flag.

If bidi-004a and bidi-004b cover all aspects of bidi- 004 (except their interaction), then bidi-004 should be given the combo flag.


ext is the file extension or format of the file. For XHTML test files, it should be xht. For HTML (non-XML) test files, it should be html.