satisfy matcher

The satisfy matcher is extremely flexible and can handle almost anything you want to specify. It passes if the block you provide returns true:

    expect(10).to satisfy { |v| v % 5 == 0 }
    expect(7).not_to satisfy { |v| v % 5 == 0 }

The default failure message (“expected [actual] to satisfy block”) is not very descriptive or helpful. To add clarification, you can provide your own description as an argument:

    expect(10).to satisfy("be a multiple of 5") do |v|
      v % 5 == 0
    end

Basic usage

Given a file named “satisfymatcherspec.rb” with:

RSpec.describe 10 do
  it { is_expected.to satisfy { |v| v > 5 } }
  it { is_expected.not_to satisfy { |v| v > 15 } }

  # deliberate failures
  it { is_expected.not_to satisfy { |v| v > 5 } }
  it { is_expected.to satisfy { |v| v > 15 } }
  it { is_expected.to_not satisfy("be greater than 5") { |v| v > 5 } }
  it { is_expected.to satisfy("be greater than 15") { |v| v > 15 } }
end

When I run rspec satisfy_matcher_spec.rb

Then the output should contain all of these:
6 examples, 4 failures
expected 10 not to satisfy expression v > 5
expected 10 to satisfy expression v > 15
expected 10 not to be greater than 5
expected 10 to be greater than 15