Implement a simple, non-interactive --watch mode
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mattbrictson
commented
Feb 19, 2024
| Listen.to(*%w[app lib test].select { |p| Dir.exist?(p) }, relative: true, &).tap(&:start) | ||
| end | ||
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| def find_matching_test_file(path) |
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🗒️ Implements a simple algorithm that matches e.g. app/models/user.rb to test/models/user_test.rb.
| @system_proc = system_proc | ||
| end | ||
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| def run(iterations: :indefinitely) |
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🗒️ Normally the watcher runs indefinitely, waiting for file system changes. The iterations arg is to support unit testing of this class, so that we can specify an upper limit on how many times the event loop is run.
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This PR introduces a
--watchmode, inspired by similar features in jest, guard, and retest.It uses the listen gem to monitor the file system for changes. When changes are detected, mighty_test uses a simple heuristic to locate the test file(s) associated with the changes. This logic is encapsulated in a new
FileSystemclass.Tests are run via an event loop. This simplifies testing, as it means the test execution happens synchronously on the main thread, even though the file system changes are detected asynchronously via a background thread managed by the listen gem. The file system changes detected in the listener thread are posted as event to the run loop, which then gets picked up and processed on the next "tick".
The event loop is implemented using Concurrent::MVar, which is essentially a blocking queue of length 1 to which events are posted and then consumed.
The tricky part of implementing this is how to handle ctrl-c. Normally when ctrl-c is pressed, all Ruby threads are interrupted with an
Interruptexception, and all child processed are killed. This includes the background process that is monitoring for file system changes.I want ctrl-c to interrupt any tests that are currently being run, but not exit the watch process. This will allow a user to interrupt a slow/stuck test and then continue TDD, without having to start the watch command again from scratch.
My solution was to
rescue Interruptwhen running tests, and then restart the file system listener (since ctrl-c will have killed its background process). This seems to work well.If a test is not currently running, then ctrl-c works normally and causes the watch process to exit.