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Testing

This document explains how to test prism, both locally, and against existing test suites.

Test suite

rake test will run all of the files in the test/ directory. This can be conceived of as two parts: unit tests, and snapshot tests.

Unit tests

These test specific prism implementation details like comments, errors, and regular expressions. There are corresponding files for each thing being tested (like test/errors_test.rb).

Snapshot tests

Snapshot tests ensure that parsed output is equivalent to previous parsed output. There are many categorized examples of valid syntax within the test/prism/fixtures/ directory. When the test suite runs, it will parse all of this syntax, and compare it against corresponding files in the test/prism/snapshots/ directory. For example, test/prism/fixtures/strings.txt has a corresponding test/prism/snapshots/strings.txt.

If the parsed files do not match, it will raise an error. If there is not a corresponding file in the test/prism/snapshots/ directory, one will be created so that it exists for the next test run.

Testing against repositories

To test the parser against a repository, you can run FILEPATHS='/path/to/repository/**/*.rb' rake lex. This will run the parser against every file matched by the glob pattern and check its generated tokens against those generated by ripper.

Local testing

As you are working, you will likely want to test your code locally. test.rb is ignored by git, so it can be used for local testing. There are also two executables which may help you:

  1. bin/lex takes a filepath and compares prism's lexed output to Ripper's lexed output. It prints any lexed output that doesn't match. It does some minor transformations to the lexed output in order to compare them, like split prism's heredoc tokens to mirror Ripper's.
$ bin/lex test.rb

If you would like to see the full lexed comparison, and not only the output that doesn't match, you can run with VERBOSE=1:

$ VERBOSE=1 bin/lex test.rb

bin/lex can also be used with -e and then source code, like this:

$ bin/lex -e "1 + 2"
  1. bin/parse takes a filepath and outputs prism's parsed node structure generated from reading the file.
$ bin/parse test.rb

bin/parse can also be used with -e and then source code, like this:

$ bin/parse -e "1 + 2"