--- title: "Test runner in Rails 5" description: "Running tests got much easier in Rails 5. Now failing tests point to line number and makes it easier to re run a failing test. There are many more goodies." canonical_url: "https://www.bigbinary.com/blog/test-runner-in-rails-5" markdown_url: "https://www.bigbinary.com/blog/test-runner-in-rails-5.md" --- # Test runner in Rails 5 Running tests got much easier in Rails 5. Now failing tests point to line number and makes it easier to re run a failing test. There are many more goodies. - Author: Prathamesh Sonpatki - Published: January 3, 2016 - Categories: Rails 5, Rails If you run `bin/rails -h` in a Rails 5 app, you will see a new command for running tests. ```bash $ bin/rails -h Usage: rails COMMAND [ARGS] The most common rails commands are: generate Generate new code (short-cut alias: "g") console Start the Rails console (short-cut alias: "c") server Start the Rails server (short-cut alias: "s") test Run tests (short-cut alias: "t") ``` Before Rails 5, we had to use `bin/rake test` to run tests. But in Rails 5, we can use `bin/rails test`. It is not just replacement of old rake task but it is backed by a `test runner` inspired from RSpec, minitest-reporters, maxitest and others. Let's see what `bin/rails test` can do. ## Running a single test Now it is possible to run a single test out of the box using the line number of the test. ```bash $ bin/rails test test/models/user_test.rb:27 ``` Rails will intelligently run the test from user_test.rb having line number 27. Note that the line number 27 does not need to be first line of the test. Below is an example. ```ruby 22: def test_valid_user 23: hash = { email: 'bob@exmaple.com', 24: first_name: 'John', 25: last_name: 'Smith' } 26: 27: user = User.new hash 28: 29: assert user.valid? 30: end ``` In the above case, `test_valid_user` can be run as long as the line number provided is between 22 and 30. ## Running multiple tests You can also pass multiple test paths and Rails will run all of those tests. ```bash $ bin/rails test test/models/user_test.rb:27 test/models/post_test.rb:42 ``` It is also possible to run all tests from a directory. ```bash $ bin/rails test test/controllers test/integration ``` ## Improved failure messages When a test fails, Rails displays a command which can be used to just run the failed test. ```bash $ bin/rails t Run options: --seed 51858 # Running: .F Failure: PostsControllerTest#test_should_get_new: Expected response to be a , but was a <302> redirect to bin/rails test test/controllers/posts_controller_test.rb:15 ``` I can simply copy `bin/rails test test/controllers/posts_controller_test.rb:15` and rerun the failing test. ## Failing fast By default when a test fails then rails reports about the test failures and then moves on to the next test. If you want to stop running the test when a test fails then use option `-f`. ```bash $ bin/rails t -f Run options: -f --seed 59599 # Running: ..F Failure: PostsControllerTest#test_should_get_new: Expected response to be a , but was a <302> redirect to bin/rails test test/controllers/posts_controller_test.rb:15 Interrupted. Exiting... Finished in 0.179125s, 16.7481 runs/s, 22.3308 assertions/s. 3 runs, 4 assertions, 1 failures, 0 errors, 0 skips ``` ## Defer test output until the end of the full test run By default when a test fails then rails prints `F` and then details about the failure like what assertion failed and how to re run the test etc. If you want to have a clean output of `.` and `F` and would like all the test failures report to come at the every end then use option `-d`. ```plaintext $ bin/rails t -d Run options: -d --seed 29906 # Running: ..F...F Finished in 0.201320s, 34.7704 runs/s, 49.6721 assertions/s. 1) Failure: PostsControllerTest#test_should_create_post [/Users/prathamesh/Projects/fun/rails-5-test-runner-app/test/controllers/posts_controller_test.rb:19]: "Post.count" didn't change by 1. Expected: 3 Actual: 2 2) Failure: PostsControllerTest#test_should_get_new [/Users/prathamesh/Projects/fun/rails-5-test-runner-app/test/controllers/posts_controller_test.rb:15]: Expected response to be a , but was a <302> redirect to 7 runs, 10 assertions, 2 failures, 0 errors, 0 skips Failed tests: bin/rails test test/controllers/posts_controller_test.rb:19 bin/rails test test/controllers/posts_controller_test.rb:15 ``` ## Better backtrace output By default when an error is encountered while running the test then the output does not contain full stacktrace. This makes debugging little bit difficult. ```plaintext Error: PostsControllerTest#test_should_create_post: NameError: undefined local variable or method `boom' for # app/controllers/posts_controller.rb:29:in `create' test/controllers/posts_controller_test.rb:20:in `block (2 levels) in ' test/controllers/posts_controller_test.rb:19:in `block in /rails-5-test-runner-app/app/controllers/posts_controller.rb:29:in `create' /sources/rails/actionpack/lib/action_controller/metal/basic_implicit_render.rb:4:in `send_action' /sources/rails/actionpack/lib/abstract_controller/base.rb:183:in `process_action' /sources/rails/actionpack/lib/action_controller/metal/rendering.rb:30:in `process_action' /sources/rails/actionpack/lib/abstract_controller/callbacks.rb:20:in `block in process_action' /sources/rails/activesupport/lib/active_support/callbacks.rb:126:in `call' ..... /sources/rails/activesupport/lib/active_support/testing/assertions.rb:71:in `assert_difference' /rails-5-test-runner-app/test/controllers/posts_controller_test.rb:19:in `block in ' ``` ## Leveraging power of Minitest The test runner also leverages power of minitest by providing some handy options. ##### Switch -s to provide your own seed Now we can also provide our own seed using `-s` switch. ```bash $ bin/rails t --s 42000 ``` #### Switch -n to run matching tests Switch `-n` will run tests matching the given string or regular expression pattern. ```plaintext $ bin/rails t -n "/create/" Run options: -n /create/ --seed 24558 # Running: E Error: PostsControllerTest#test_should_create_post: NameError: undefined local variable or method `boom' for # app/controllers/posts_controller.rb:29:in `create' test/controllers/posts_controller_test.rb:20:in `block (2 levels) in ' test/controllers/posts_controller_test.rb:19:in `block in ' bin/rails test test/controllers/posts_controller_test.rb:18 Finished in 0.073857s, 13.5396 runs/s, 0.0000 assertions/s. 1 runs, 0 assertions, 0 failures, 1 errors, 0 skips ``` #### Verbose output It is also possible to see the verbose output using `-v` switch. It shows time required to run each test. This would help in detecting slow running tests. ```plaintext $ bin/rails t -v Run options: -v --seed 30118 # Running: PostsControllerTest#test_should_destroy_post = 0.07 s = . PostsControllerTest#test_should_update_post = 0.01 s = . PostsControllerTest#test_should_show_post = 0.10 s = . PostsControllerTest#test_should_create_post = 0.00 s = F Failure: PostsControllerTest#test_should_create_post: "Post.count" didn't change by 1. Expected: 3 Actual: 2 bin/rails test test/controllers/posts_controller_test.rb:19 PostsControllerTest#test_should_get_new = 0.02 s = . PostsControllerTest#test_should_get_index = 0.01 s = . PostsControllerTest#test_should_get_edit = 0.00 s = . Finished in 0.210071s, 33.3220 runs/s, 47.6028 assertions/s. 7 runs, 10 assertions, 1 failures, 0 errors, 0 skips ``` ### Colored output Now by default we will get colored output. No need to add additional gem to colored output. ![colored test output](https://www.bigbinary.com/blog/images/images_used_in_blog/2016/test-runner-in-rails-5/rails_5_test_runner.png) With all these awesome features, testing Rails 5 apps has definitely become a better experience. Rails has shipped all these features within the framework itself so you don't have to use multiple gems and libraries to achieve all of these things. ## Links - [Human page](https://www.bigbinary.com/blog/test-runner-in-rails-5)