Experiment that adds `.is` (like the old RSpec `.should`) to Minitest

dot_is_for_minitest.rb

require 'minitest/autorun'

module DotIs
  # Track the current test so that we can run assertions in its context
  def self.current_test=(test)
    Thread.current[:dot_is_current_test] = test
  end

  def self.current_test
    Thread.current.fetch :dot_is_current_test
  end


  # Override lifecycle hooks so we can access the current test
  def before_setup(*)
    DotIs.current_test = self
    super
  end
  
  MiniTest::Test.include self


  # Add `.is` to BasicObject (essentially, the old `.should` from RSpec)
  refine BasicObject do
    def is(expected)
      DotIs.current_test.assert_equal(expected, self)
    end
  end
end


describe 'some tests' do
  # Just b/c I think the output, ".F" is easier to understand
  i_suck_and_my_tests_are_order_dependent!

  # Lets us call `.is` on any object, but only from within this scope
  using DotIs 

  it 'passes this test and knows about the assertion' do
    (1+2).is 3
  end

  it 'fails this test and reports the failure' do
    (1+2).is 4
  end
end

# Just showing that the refinement means `.is` doesn't exist outside that scope
begin
  (1+2).is 3
rescue NoMethodError => e
  e # => #<NoMethodError: undefined method `is' for 3:Integer\nDid you mean?  i>
end

# >> Run options: --seed 21958
# >> 
# >> # Running:
# >> 
# >> .F
# >> 
# >> Failure:
# >> some tests#test_0002_fails this test and reports the failure [program.rb:26]:
# >> Expected: 4
# >>   Actual: 3
# >> 
# >> bin/rails test program.rb:43
# >> 
# >> 
# >> 
# >> Finished in 0.001340s, 1492.5374 runs/s, 1492.5374 assertions/s.
# >> 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips