Feature: `contain_exactly` matcher

  The `contain_exactly` matcher provides a way to test arrays against each other in a way
  that disregards differences in the ordering between the actual and expected array.
  For example:

  ```ruby
    expect([1, 2, 3]).to    contain_exactly(2, 3, 1) # pass
    expect([:a, :c, :b]).to contain_exactly(:a, :c ) # fail
  ```

  This matcher is also available as `match_array`, which expects the expected array to be
  given as a single array argument rather than as individual splatted elements. The above
  could also be written as:

  ```ruby
    expect([1, 2, 3]).to    match_array [2, 3, 1] # pass
    expect([:a, :c, :b]).to match_array [:a, :c]  # fail
  ```

  Scenario: Array is expected to contain every value
    Given a file named "contain_exactly_matcher_spec.rb" with:
      """ruby
      RSpec.describe [1, 2, 3] do
        it { is_expected.to contain_exactly(1, 2, 3) }
        it { is_expected.to contain_exactly(1, 3, 2) }
        it { is_expected.to contain_exactly(2, 1, 3) }
        it { is_expected.to contain_exactly(2, 3, 1) }
        it { is_expected.to contain_exactly(3, 1, 2) }
        it { is_expected.to contain_exactly(3, 2, 1) }

        # deliberate failures
        it { is_expected.to contain_exactly(1, 2, 1) }
      end
      """
     When I run `rspec contain_exactly_matcher_spec.rb`
     Then the output should contain "7 examples, 1 failure"
      And the output should contain:
      """
           Failure/Error: it { is_expected.to contain_exactly(1, 2, 1) }

             expected collection contained:  [1, 1, 2]
             actual collection contained:    [1, 2, 3]
             the missing elements were:      [1]
             the extra elements were:        [3]
      """

  Scenario: Array is not expected to contain every value
    Given a file named "contain_exactly_matcher_spec.rb" with:
      """ruby
      RSpec.describe [1, 2, 3] do
        it { is_expected.to_not contain_exactly(1, 2, 3, 4) }
        it { is_expected.to_not contain_exactly(1, 2) }

        # deliberate failures
        it { is_expected.to_not contain_exactly(1, 3, 2) }
      end
      """
     When I run `rspec contain_exactly_matcher_spec.rb`
     Then the output should contain "3 examples, 1 failure"
      And the output should contain:
      """
           Failure/Error: it { is_expected.to_not contain_exactly(1, 3, 2) }
             expected [1, 2, 3] not to contain exactly 1, 3, and 2
      """
