Minitest for Crystal

Unit tests and assertions for the Crystal programming language, using the fantastic minitest as reference.

The minitest rationale brings a number of benefits over stdlib spec:

• Test suites (and describe blocks) are simple classes. Build a test suite hierarchy, add methods and include modules without polluting the global namespace, and don't impact other test suites.
• One module per suite, not everything in a single module (faster codegen).
• Simple assertions and expect expectations.

Increase the trust in your program's correctness:

• Test suites run concurrently to each others.
• Test suites run in parallel to each others.
• Tests run in random order by default — use seed for reproducible runs.
• Chaos mode to flatten tests and randomize everything (full random, full concurrent, full parallel).

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

Define your tests as methods beginning with test_:

require "minitest/autorun"

class MemeTest < Minitest::Test
  def meme
    @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

Specs follow the same design rationale as the original Minitest: describe generates classes that inherit from Minitest::Spec, and it generates test methods.

require "minitest/autorun"

describe Meme do
  let(:meme) { Meme.new }

  describe "when asked about cheeseburgers" do
    it "must respond positively" do
      expect(meme.i_can_has_cheezburger?).must_equal("OHAI!")
    end
  end

  describe "when asked about blending possibilities" do
    it "won't say no" do
      expect(meme.will_it_blend?).wont_match(/^no/i)
    end
  end
end

You may use assertions in your specs (they're the same) or you may prefer to skip the expect syntax at the expense of polluting Object (legacy, discouraged):

class Object
  include Minitest::Expectations
end

meme.i_can_haz_cheezeburger?.must_equal("OHAI!")
meme.will_it_blend?.wont_match(/^no/i)

Eventually run the tests:

$ crystal run test/meme_test.cr spec/meme_spec.cr -- --verbose

You may filter your tests using an exact test name, or a regexp:

$ crystal run test/meme_test.cr -- -n test_that_kitty_can_eat
$ crystal run test/meme_test.cr -- -n /will/

Distributed under the MIT License. Please see LICENSE for details.

• Julien Portalier @ysbaddaden for the Crystal implementation
• Ryan Davis @zenspider and seattle.rb for the original Ruby gem