Comparison matchers

RSpec provides a number of matchers that are based on Ruby's built-in operators. These can be used for generalized comparison of values. E.g.

expect(9).to be > 6
expect(3).to be <= 3
expect(1).to be < 6
expect('a').to be < 'b'

Numeric operator matchers

Given a file named "numeric_operator_matchers_spec.rb" with:

RSpec.describe 18 do
  it { is_expected.to be < 20 }
  it { is_expected.to be > 15 }
  it { is_expected.to be <= 19 }
  it { is_expected.to be >= 17 }

  # deliberate failures
  it { is_expected.to be < 15 }
  it { is_expected.to be > 20 }
  it { is_expected.to be <= 17 }
  it { is_expected.to be >= 19 }
  it { is_expected.to be < 'a' }
end

RSpec.describe 'a' do
  it { is_expected.to be < 'b' }

  # deliberate failures
  it { is_expected.to be < 18 }
end

When I run rspec numeric_operator_matchers_spec.rb

Then the output should contain "11 examples, 6 failures"

And the output should contain:

     Failure/Error: it { is_expected.to be < 15 }

       expected: < 15
            got:   18

And the output should contain:

     Failure/Error: it { is_expected.to be > 20 }

       expected: > 20
            got:   18

And the output should contain:

     Failure/Error: it { is_expected.to be <= 17 }

       expected: <= 17
            got:    18

And the output should contain:

     Failure/Error: it { is_expected.to be >= 19 }

       expected: >= 19
            got:    18

And the output should contain:

     Failure/Error: it { is_expected.to be < 'a' }

       expected: < "a"
            got:   18

And the output should contain:

     Failure/Error: it { is_expected.to be < 18 }

       expected: < 18
            got:   "a"

String operator matchers

Given a file named "string_operator_matchers_spec.rb" with:

RSpec.describe "Strawberry" do
  it { is_expected.to be < "Tomato" }
  it { is_expected.to be > "Apple" }
  it { is_expected.to be <= "Turnip" }
  it { is_expected.to be >= "Banana" }

  # deliberate failures
  it { is_expected.to be < "Cranberry" }
  it { is_expected.to be > "Zuchini" }
  it { is_expected.to be <= "Potato" }
  it { is_expected.to be >= "Tomato" }
end

When I run rspec string_operator_matchers_spec.rb

Then the output should contain "8 examples, 4 failures"

And the output should contain:

     Failure/Error: it { is_expected.to be < "Cranberry" }

       expected: < "Cranberry"
            got:   "Strawberry"

And the output should contain:

     Failure/Error: it { is_expected.to be > "Zuchini" }

       expected: > "Zuchini"
            got:   "Strawberry"

And the output should contain:

     Failure/Error: it { is_expected.to be <= "Potato" }

       expected: <= "Potato"
            got:    "Strawberry"

And the output should contain:

     Failure/Error: it { is_expected.to be >= "Tomato" }

       expected: >= "Tomato"
            got:    "Strawberry"