Question

I have a line in my test:

page.has_reply?("my reply").must_equal true

and to make it more readable I want to use a custom matcher:

page.must_have_reply "my reply"

Based on the docs for https://github.com/zenspider/minitest-matchers I expect I need to write a matcher which looks something like this:

def have_reply(text)
  subject.has_css?('.comment_body', :text => text)
end
MiniTest::Unit::TestCase.register_matcher :have_reply, :have_reply

The problem is that I can’t see how to get a reference to the subject (i.e. the page object). The docs say “Note subject must be the first argument in assertion” but that doesn’t really help.

Answer 1

There is a little example, you can create a class which should responds to set of methods matches?, failure_message_for_should, failure_message_for_should_not.
In matches? method you can get the reference to the subject.

class MyMatcher
  def initialize(text)
    @text = text
  end

  def matches? subject
    subject =~ /^#{@text}.*/
  end

  def failure_message_for_should
    "expected to start with #{@text}"
  end

  def failure_message_for_should_not
    "expected not to start with #{@text}"
  end
end

def start_with(text)
  MyMatcher.new(text)
end
MiniTest::Unit::TestCase.register_matcher :start_with, :start_with

describe 'something' do
  it 'must start with...' do
    page = 'my reply'
    page.must_start_with 'my reply'
    page.must_start_with 'my '
  end
end