# JavaScript tests with expected outputTests in test/message pass if the output matches the expected output. Messagetests are particularly useful when checking for exact error messages.Tests and their expected output must have the same filename, with the `.js` and`.out` extension.```foo.jsfoo.out```**All tests must end with an exception**. The test runner does nothandle output from multiple runs, e.g., `--stress-opt`. Without an exception,the output will be generated several times and the comparison will fail.You can use a regex in the expected output. Instead of the exactpath. use```*%(basename)s:7: SyntaxError: Detected cycle while resolving name 'a'```Empty lines are ignored in the comparison, but whitespaces are not.Exact details of the test runner are in [testcfg.py](testcfg.py).