Main file containing your custom matchers

spec_custom_matchers.rb

# Custom matchers
module CustomMatchers
    class TimeTaken
        def initialize(lower_seconds, upper_seconds=nil)
            @lower_seconds = lower_seconds
            @upper_seconds = upper_seconds
        end
    
        def matches?(given_proc)
            range = @lower_seconds..@upper_seconds
            start = Time.now
            given_proc.call
            fin = Time.now
            @diff = fin - start
            range.include?(@diff)
        end

        def and(upper_seconds)
            @upper_seconds = upper_seconds
            self
        end
        
        # syntactic sugar
        def seconds
            self
        end
    
        def failure_message_for_should
            "expected block to take between #{@lower_seconds} and #{@upper_seconds} seconds, but took #{@diff} seconds"
        end
    
        def failure_message_for_should_not
            "expected block not to take between #{@lower_seconds} and #{@upper_seconds} seconds, but took #{@diff} seconds"
        end    
    end

    def take_between(lower_seconds, upper_seconds=nil)
        TimeTaken.new(lower_seconds, upper_seconds)
    end
end