AWS Developer Blog

From Minitest::Spec to Minitest::Test

by Trevor Rowe | on | in Ruby | Permalink | Comments |  Share

In a previous blog post, I introduced Minitest from the perspective of RSpec. Some Minitest users prefer to avoid the specification style of Minitest::Spec. Instead they use Minitest::Test. It’s closer to the metal and uses a more vanilla Ruby syntax.

Here is an example spec file using Minitest::Spec:

require 'spec_helper'

describe MyClass do
  describe '#some_method' do
    it 'returns a string' do
      MyClass.new.some_method.must_be_kind_of(String)
    end
  end
end

Converting this to use Minitest::Test looks like:

require 'test_helper'

class MyClassTest < Minitest::Test
  def test_some_method_returns_a_string
    assert_kind_of String, MyClass.new.some_method
  end
end

Some key differences:

  • Assertions are instance methods provided by the test class. Instead of calling magic methods added to Object, you pass the object under test into the assertion. Example:

    value.must_be_kind_of(String)
    

    becomes:

    assert_kind_of(String, value) 
    
  • There is no DSL for defining test cases. The it method is removed. Instead, all methods prefixed with test_ are executed as test cases.

  • Nesting describe blocks is a useful technique for grouping specs. You can still do this, but you have to nest test classes.

    class MyClassTest < Minitest::Test
        class SubClassTest < Minitest::Test
        ...
      end
    end
    

I don’t feel as strongly as others about using vanilla Minitest::Test over Minitest::Spec. I personally find the specs easier to read, but that may be due to my experience with RSpec. You may have a different experience based on your testing background.

Happy Testing!