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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 "satisfy_matcher_spec.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 |