As prerequisite to T288498, we should fist straighten out the compliance test to match the promised version. After that, we can star to cleanly port tests and features one by one in a fast-forward manner.

Problem

We currently run a mixture of the Less.js v1.5, v1.6, and v2.5 tests in the less.php Git repository. These are located in the /test/Fixtures/ directory, and verified by the /test/phpunit/FixturesTest.php.

Scope of work

• Add the data files from Less.js 2.5.3 ("less", "data", and "css" directory), and register them in FixturesTest.php. Use test/compare.php to find differences and document them in KNOWN_FAILURE to exclude them from CI.
• Remove the old lessjs/, lessjs (1.6)/ and , lessjs (1.5)/ data files, and update any remaining references to those in the Git repo to refer to lessjs-2.5.3 instead.
• Review known differences with the team, and create subtasks under T288498 for the ones we want to change. Some behaviours are intentionally different for security reasons (such as JS-eval and JS-plugin support). For the differences we want to add support for, we create tasks for each kind of difference (multiple output differences likely relate to the same behaviour difference, we can take a guess which ones are related, and look more closely when we work on each task).