Update README.md

README.md

@@ -76,9 +76,55 @@ Run `just deps` to install the cargo dev dependencies, which right now is only
 
 ### Test Suite
 
-To run the tests, run `just run` in tests/. Cargo will build and run the project, which
-is a simple test-runner in the `main` fn. If you're going to do more than a simple
-change, I recommend calling `just watch` in tests/, which will watch for any changes in
-the whole repo and re-run the test suite. If you want to only run or watch a single test file, you
-can specify the name by passing an argument to `run` or `watch`: `just run
-recipe-dependency`.
+`vim-just` includes automated tests of its syntax highlighting and filetype detection.
+Running the tests invokes Cargo to build and run the project, which
+is a simple test-runner in the `main` fn.
+
+To run the syntax highlighting tests, run `just run` in tests/.
+If you want to run only a subset of the syntax highlighting tests,
+you can pass an optional regex parameter to `just run` matching the filenames you want to include:
+
+```bash
+# run only the 'kitchen-sink.just' syntax highlighting test
+$ just run kitchen-sink
+...
+test kitchen-sink…
+ok
+
+# run the syntax highlighting tests with base filenames matching the regex ^\w+$
+$ just run '^\w+$'
+...
+test comment…
+ok
+test deprecated_obsolete…
+ok
+test invalid…
+ok
+test set…
+ok
+test tricky…
+ok
+```
+
+Note that the `.just` extension is trimmed off before matching against the regex.
+
+To run the filetype detection tests, run `just ftdetect` in tests/.
+
+If you're going to do more than a simple change, I recommend calling `just watch` in tests/,
+which will watch for any changes in the whole repo and re-run the test suite.
+By default, it will run the syntax highlighting tests.
+`just watch` accepts up to two parameters to customize which tests to watch:
+
+```bash
+# watch all syntax highlighting tests (default)
+$ just watch
+
+# watch ftdetect tests
+$ just watch ftdetect
+
+# watch all tests
+$ just watch ftdetect run
+
+# watch syntax highlighting tests with filenames matching the regex ^r.*s$
+$ just watch run '^r.*s$'
+```