# File lib/rspec/matchers/built_in/yield.rb, line 51 def assert_used! return if @used raise "You must pass the argument yielded to your expect block on " + "to the method-under-test as a block. It acts as a probe that " + "allows the matcher to detect whether or not the method-under-test " + "yields, and, if so, how many times, and what the yielded arguments " + "are." end