minitest provides a complete suite of testing facilities supporting TDD, BDD, mocking, and benchmarking.
"I had a class with Jim Weirich on testing last week and we were allowed to choose our testing frameworks. Kirk Haines and I were paired up and we cracked open the code for a few test frameworks... I MUST say that minitest is *very* readable / understandable compared to the 'other two' options we looked at. Nicely done and thank you for helping us keep our mental sanity." -- Wayne E. Seguin
minitest/unit is a small and incredibly fast unit testing framework. It provides a rich set of assertions to make your tests clean and readable.
minitest/spec is a functionally complete spec engine. It hooks onto minitest/unit and seamlessly bridges test assertions over to spec expectations.
minitest/benchmark is an awesome way to assert the performance of your algorithms in a repeatable manner. Now you can assert that your newb co-worker doesn't replace your linear algorithm with an exponential one!
minitest/mock by Steven Baker, is a beautifully tiny mock (and stub) object framework.
minitest/pride shows pride in testing and adds coloring to your test output. I guess it is an example of how to write IO pipes too. :P
minitest/unit is meant to have a clean implementation for language implementors that need a minimal set of methods to bootstrap a working test suite. For example, there is no magic involved for test-case discovery.
"Again, I can't praise enough the idea of a testing/specing framework that I can actually read in full in one sitting!" -- Piotr Szotkowski
Comparing to rspec:
rspec is a testing DSL. minitest is ruby. -- Adam Hawkins, "Bow Before MiniTest"
minitest doesn't reinvent anything that ruby already provides, like: classes, modules, inheritance, methods. This means you only have to learn ruby to use minitest and all of your regular OO practices like extract-method refactorings still apply.
minitest/autorun - the easy and explicit way to run all your tests.
minitest/unit - a very fast, simple, and clean test system.
minitest/spec - a very fast, simple, and clean spec system.
minitest/mock - a simple and clean mock/stub system.
minitest/benchmark - an awesome way to assert your algorithm's performance.
minitest/pride - show your pride in testing!
Incredibly small and fast runner, but no bells and whistles.
See design_rationale.rb to see how specs and tests work in minitest.
Given that you'd like to test the following class:
class Meme def i_can_has_cheezburger? "OHAI!" end def will_it_blend? "YES!" end end
Unit tests¶ ↑
Define your tests as methods beginning with `test_`.
require "minitest/autorun" class TestMeme < Minitest::Test def setup @meme = Meme.new end def test_that_kitty_can_eat assert_equal "OHAI!", @meme.i_can_has_cheezburger? end def test_that_it_will_not_blend refute_match /^no/i, @meme.will_it_blend? end def test_that_will_be_skipped skip "test this later" end end
require "minitest/autorun" describe Meme do before do @meme = Meme.new end describe "when asked about cheeseburgers" do it "must respond positively" do @meme.i_can_has_cheezburger?.must_equal "OHAI!" end end describe "when asked about blending possibilities" do it "won't say no" do @meme.will_it_blend?.wont_match /^no/i end end end
For matchers support check out:
Add benchmarks to your tests.
# optionally run benchmarks, good for CI-only work! require "minitest/benchmark" if ENV["BENCH"] class TestMeme < Minitest::Benchmark # Override self.bench_range or default range is [1, 10, 100, 1_000, 10_000] def bench_my_algorithm assert_performance_linear 0.9999 do |n| # n is a range value @obj.my_algorithm(n) end end end
Or add them to your specs. If you make benchmarks optional, you'll need to wrap your benchmarks in a conditional since the methods won't be defined. In minitest 5, the describe name needs to match /Bench(mark)?$/.
describe "Meme Benchmark" do if ENV["BENCH"] then bench_performance_linear "my_algorithm", 0.9999 do |n| 100.times do @obj.my_algorithm(n) end end end end
outputs something like:
# Running benchmarks: TestBlah 100 1000 10000 bench_my_algorithm 0.006167 0.079279 0.786993 bench_other_algorithm 0.061679 0.792797 7.869932
Output is tab-delimited to make it easy to paste into a spreadsheet.
class MemeAsker def initialize(meme) @meme = meme end def ask(question) method = question.tr(" ","_") + "?" @meme.__send__(method) end end require "minitest/autorun" describe MemeAsker do before do @meme = Minitest::Mock.new @meme_asker = MemeAsker.new @meme end describe "#ask" do describe "when passed an unpunctuated question" do it "should invoke the appropriate predicate method on the meme" do @meme.expect :will_it_blend?, :return_value @meme_asker.ask "will it blend" @meme.verify end end end end
def test_stale_eh obj_under_test = Something.new refute obj_under_test.stale? Time.stub :now, Time.at(0) do # stub goes away once the block is done assert obj_under_test.stale? end end
A note on stubbing: In order to stub a method, the method must actually exist prior to stubbing. Use a singleton method to create a new non-existing method:
def obj_under_test.fake_method ... end
Running Your Tests¶ ↑
Ideally, you'll use a rake task to run your tests, either piecemeal or all at once. Both rake and rails ship with rake tasks for running your tests. BUT! You don't have to:
% ruby -Ilib:test test/minitest/test_minitest_unit.rb Run options: --seed 37685 # Running: ...................................................................... (etc) Finished in 0.107130s, 1446.8403 runs/s, 2959.0217 assertions/s. 155 runs, 317 assertions, 0 failures, 0 errors, 0 skips
There are runtime options available, both from minitest itself, and also provided via plugins. To see them, simply run with `–help`:
% ruby -Ilib:test test/minitest/test_minitest_unit.rb --help minitest options: -h, --help Display this help. -s, --seed SEED Sets random seed -v, --verbose Verbose. Show progress processing files. -n, --name PATTERN Filter run on /pattern/ or string. Known extensions: pride, autotest -p, --pride Pride. Show your testing pride! -a, --autotest Connect to autotest server.
Writing Extensions¶ ↑
To define a plugin, add a file named minitest/XXX_plugin.rb to your project/gem. Minitest will find and require that file using Gem.find_files. It will then try to call plugin_XXX_init during startup. The option processor will also try to call plugin_XXX_options passing the OptionParser instance and the current options hash. This lets you register your own command-line options. Here's a totally bogus example:
# minitest/bogus_plugin.rb: module Minitest def self.plugin_bogus_options(opts, options) opts.on "--myci", "Report results to my CI" do options[:myci] = true options[:myci_addr] = get_myci_addr options[:myci_port] = get_myci_port end end def self.plugin_bogus_init(options) self.reporter << MyCI.new(options) if options[:myci] end end
Adding custom reporters¶ ↑
Minitest uses composite reporter to output test results using multiple
reporter instances. You can add new reporters to the composite during the
init_plugins phase. As we saw in
plugin_bonus_init above, you
simply add your reporter instance to the composite via +<<+.
AbstractReporter defines the API for reporters. You may
subclass it and override any method you want to achieve your desired
Called when the run has started.
Called for each result, passed or otherwise.
Called at the end of the run.
Called to see if you detected any problems.
Using our example above, here is how we might implement MyCI:
# minitest/bogus_plugin.rb module Minitest class MyCI < AbstractReporter attr_accessor :results, :addr, :port def initialize options self.results =  self.addr = options[:myci_addr] self.port = options[:myci_port] end def record result self.results << result end def report CI.connect(addr, port).send_results self.results end end end
How to test SimpleDelegates?¶ ↑
The following implementation and test:
class Worker < SimpleDelegator def work end end describe Worker do before do @worker = Worker.new(Object.new) end it "must respond to work" do @worker.must_respond_to :work end end
outputs a failure:
1) Failure: Worker#test_0001_must respond to work [bug11.rb:16]: Expected #<Object:0x007f9e7184f0a0> (Object) to respond to #work.
Worker is a SimpleDelegate which in 1.9+ is a subclass of BasicObject. Expectations are put on Object (one level down) so the Worker (SimpleDelegate) hits `method_missing` and delegates down to the `Object.new` instance. That object doesn't respond to work so the test fails.
You can bypass `SimpleDelegate#method_missing` by extending the worker with `Minitest::Expectations`. You can either do that in your setup at the instance level, like:
before do @worker = Worker.new(Object.new) @worker.extend Minitest::Expectations end
or you can extend the Worker class (within the test file!), like:
class Worker include ::Minitest::Expectations end
How to share code across test classes?¶ ↑
Use a module. That's exactly what they're for:
module UsefulStuff def useful_method # ... end end describe Blah do include UsefulStuff def test_whatever # useful_method available here end end
Remember, `describe` simply creates test classes. It's just ruby at the end of the day and all your normal Good Ruby Rules (tm) apply. If you want to extend your test using setup/teardown via a module, just make sure you ALWAYS call super. before/after automatically call super for you, so make sure you don't do it twice.
Prominent Projects using Minitest:¶ ↑
rails (active_support et al)
…and of course, everything from seattle.rb…
Known Extensions:¶ ↑
Bridge between Capybara RSpec matchers and Minitest::Spec expectations (e.g. page.must_have_content(“Title”)).
Metadata for describe/it blocks (e.g. `it “requires JS driver”, js: true do`)
Colorize minitest output with ANSI colors.
Around block for minitest. An alternative to setup/teardown dance.
Adds support for RSpec-style let! to immediately invoke let statements before each test.
Helps you isolate and debug random test failures.
Assertions and expectations for testing Capistrano recipes.
Capybara matchers support for minitest unit and spec.
Run Minitest suites as Chef report handlers
CI reporter plugin for Minitest.
Colorize Minitest output and show failing tests instantly.
Defines contexts for code reuse in Minitest specs that share common expectations.
Wraps assert so failed assertions drop into the ruby debugger.
Patches Minitest to allow for an easily configurable output.
Minimal documentation format inspired by rspec's.
Detailed output inspired by rspec's documentation format.
Print out emoji for your test passes, fails, and skips.
Semantically symmetric aliases for assertions and expectations.
Clean API for excluding certain tests you don't want to run under certain conditions.
Adds assertion and expectation to help testing filesystem contents.
Makes your Minitest mocks more resilient.
Generally useful additions to minitest's assertions and expectations.
Test notifier for minitest via growl.
Implicit declaration of the test subject.
Instrument ActiveSupport::Notifications when test method is executed.
Store information about speed of test execution provided by minitest-instrument in database.
Test notifier for minitest via libnotify.
Run test at line number.
Provides extensions to minitest for macruby UI testing.
Adds support for RSpec-style matchers to minitest.
Annotate tests with metadata (key-value).
Mongoid assertion matchers for Minitest.
Provides must_not as an alias for wont in Minitest.
Test notifier for minitest via Mountain Lion's Notification Center.
Run tests in parallel with a single database.
PowerAssert for Minitest.
Adds support for .predicate? methods.
Minitest integration for Rails 3.x.
Capybara integration for Minitest::Rails.
Create customizable Minitest output formats.
Colored red/green output for Minitest.
Use RSpec Mocks with Minitest.
RSpec-style +x.should == y+ assertions for Minitest.
Adding all manner of shoulds to Minitest (bad idea)
Provides rspec-ish context method to Minitest::Spec.
Expect syntax for Minitest::Spec (e.g. expect(sequences).to_include :celery_man).
Minitest::Spec extensions for Rails and beyond.
Drop in Minitest::Spec superclass for ActiveSupport::TestCase.
Find leaking state between tests
Stub any instance of a method on the given class for the duration of a block.
Stub constants for the duration of a block.
Add tags for minitest.
Automatic cassette managment with Minitest::Spec and VCR.
Yet another test colorizer.
Get tests results as a TestResult object.
Shoulda style syntax for minitest test::unit.
Bridges between test/unit and minitest.
Minitest matchers for Mongoid.
A pry plugin w/ minitest support. See pry-rescue/minitest.rb.
Easily translate any RSpec matchers to Minitest assertions and expectations.
Unknown Extensions:¶ ↑
Authors… Please send me a pull request with a description of your minitest extension.
Ruby 1.8.7+. No magic is involved. I hope.
sudo gem install minitest
On 1.9, you already have it. To get newer candy you can still install the gem, and then requiring “minitest/autorun” should automatically pull it in. If not, you'll need to do it yourself:
gem "minitest" # ensures you"re using the gem, and not the built-in MT require "minitest/autorun" # ... usual testing stuffs ...
DO NOTE: There is a serious problem with the way that ruby 1.9/2.0 packages their own gems. They install a gem specification file, but don't install the gem contents in the gem path. This messes up Gem.find_files and many other things (gem which, gem contents, etc).
Just install minitest as a gem for real and you'll be happier.
(The MIT License)
Copyright © Ryan Davis, seattle.rb
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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