covet

Covet

What Is It?

It's a regression test selection tool for ruby, an implementation of some ideas by Mr. Tenderlove expressed here.

How Does It Work?

Reading the article will give you a good idea, but here's a short summary:

1. Gather coverage information during test runs, before and after each test method in order to know which test methods ran which files and lines of the tested application code.

2. Change the application code.

3. Covet shows you which tests to run based on the coverage information gathered in step 1, and the fact that git knows that you changed certain lines of the application code.

Usage

Add covet to your Gemfile in your test or development :group, or:

$ gem install covet

Coverage Collection:

Run your test suite with coverage collection on. To enable this, add require 'covet' before any tests run (in a test helper file or similar), and run your suite with: covet -c $CMD, where $CMD is the command to run your test suite. Example:

$ covet -c "rake test"

Covet should output a message before any other message:

Collecting coverage information for each test method...

By default, covet hooks into minitest and collects coverage before and after each method. If you're using rspec, make sure to pass the -t option:

$ covet -t rspec -c "rake test"

After this, you should have 2 new files: run_log.json, and run_log_index.json.

Now, by default the covet command will print out which test files should be run based off the changes in your git repo since the last commit.

For example:

$ covet

You need to run:
- /home/luke/Desktop/code/rails/activesupport/test/test\_case\_test.rb

To execute the run list, simply:

$ covet -e

Testing Gems

By default, covet removes all standard library and gem files from the run_log, because it assumes you're testing your own library code. In order to test a gem, you need to add the --whitelist-gems option. For example:

$ covet -c "rake test" --whitelist-gems "activesupport,rails"

Caveats/Bugs

1. It's not tested thoroughly enough.

2. Don't rely on this library to be correct yet (ie: don't forgo full test suite runs before committing to a repository). It's still early days. Please contribute code, docs, or ideas, though!