Method: Spec::Matchers#wrap_expectation

Defined in:
lib/spec/matchers/wrap_expectation.rb

#wrap_expectation(matcher, &block) ⇒ Object

wraps an expectation in a block that will return true if the expectation passes and false if it fails (without bubbling up the failure).

This is intended to be used in the context of a simple matcher, and is especially useful for wrapping multiple expectations or one or more assertions from test/unit extensions when running with test/unit.

Examples

def eat_cheese(cheese)
  simple_matcher do |mouse, matcher|
    matcher.failure_message = "expected #{mouse} to eat cheese"
    wrap_expectation do |matcher|
      assert_eats_cheese(mouse)
    end
  end
end

describe Mouse do
  it "eats cheese" do
    Mouse.new.should eat_cheese
  end
end

You might be wondering “why would I do this if I could just say” assert_eats_cheese?“, a fair question, indeed. You might prefer to replace the word assert with something more aligned with the rest of your code examples. You are using rspec, after all.

The other benefit you get is that you can use the negative version of the matcher:

describe Cat do
  it "does not eat cheese" do
    Cat.new.should_not eat_cheese
  end
end

So in the event there is no assert_does_not_eat_cheese available, you’re all set!



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# File 'lib/spec/matchers/wrap_expectation.rb', line 45

def wrap_expectation(matcher, &block)
  begin
    block.call(matcher)
    return true
  rescue Exception => e
    matcher.failure_message = e.message
    return false
  end
end