Every folder in fixtures represents a test. The file that starts with 1. is diffed against the file that starts with 2.. Use tst instead of ts to avoid compiler/linter errors for typescript diff files.

• Missing *.expected.diff.json are created automatically (as well as an *.invalid.diff.json file).
• If the actual diff does not equal the expected diff, the expected file is updated automatically. The previous value of the expected file is written to *.invalid.diff.json.
• The test will fail if there are any *.invalid.diff.json files. This makes sure that the test keeps failing even if it is run a second time.

When changing the diffing algorithm, run the fixture tests, review the diff of the *.expected.diff.json files and delete all *.invalid.diff.json files.