Commit 2e83b562 authored by Robert Speicher's avatar Robert Speicher

Add a section about `let` to the Testing guide

[ci skip]
parent 60f4081e
......@@ -11,8 +11,7 @@ importance.
## Factories
GitLab uses [factory_girl] as a test
fixture replacement.
GitLab uses [factory_girl] as a test fixture replacement.
- Factory definitions live in `spec/factories/`, named using the pluralization
of their corresponding model (`User` factories are defined in `users.rb`).
......@@ -65,8 +64,30 @@ the command line via `bundle exec teaspoon`, or via a web browser at
- Don't `describe` symbols (see [Gotchas](gotchas.md#dont-describe-symbols)).
- Prefer `not_to` to `to_not`.
- Try to match the ordering of tests to the ordering within the class.
- Try to follow the [Four-Phase Test](https://robots.thoughtbot.com/four-phase-test)
pattern, using newlines to separate phases.
- Try to follow the [Four-Phase Test][four-phase-test] pattern, using newlines
to separate phases.
[four-phase-test]: https://robots.thoughtbot.com/four-phase-test
### `let` variables
GitLab's RSpec suite has made extensive use of `let` variables to reduce
duplication. However, this sometimes [comes at the cost of clarity][lets-not],
so we need to set some guidelines for their use going forward:
- `let` variables are preferable to instance variables. Local variables are
preferable to `let` variables.
- Use `let` to reduce duplication throughout an entire spec file.
- Don't use `let` to define variables used by a single test; define them as
local variables inside the test's `it` block.
- Don't define a `let` variable inside the top-level `describe` block that's
only used in a more deeply-nested `context` or `describe` block. Keep the
definition as close as possible to where it's used.
- Try to avoid overriding the definition of one `let` variable with another.
- Don't define a `let` variable that's only used by the definition of another.
Use a helper method instead.
[lets-not]: https://robots.thoughtbot.com/lets-not
### Test speed
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