Useful assertions for unit testing.

assert_differences.rb

module Test::Unit::Extensions

  module AssertDifferences

    # assert_stable_count(Person) <=> assert_no_difference("Person.count")
    def assert_stable_count(expression, &block)
      assert_same_count(expressify_class(expression), &block)
    end

    # assert_removed(Person) <=> assert_difference("Person.count", -1)
    def assert_removed(expression, counter = 1, &block)
      assert_less(expressify_class(expression), counter, &block)
    end

    # assert_added(Person) <=> assert_difference("Person.count", 1)
    def assert_added(expression, counter = 1, &block)
      assert_more(expressify_class(expression), counter, &block)
    end

    

    # assert_same_count("Person") <=> assert_no_difference("Person.count")
    def assert_same_count(expression, &block)
      assert_no_difference(countify_expression(expression), &block)
    end

    # assert_less("Person") <=> assert_difference("Person.count", -1)
    def assert_less(expression, counter = 1, &block)
      assert_difference(countify_expression(expression), counter * -1, &block)
    end

    # assert_more("Person") <=> assert_difference("Person.count", 1)
    def assert_more(expression, counter = 1, &block)
      assert_difference(countify_expression(expression), counter, &block)
    end


    protected
    

    def expressify_class(expression)
      return expression.name if expression.is_a?(Class)
      return expression
    end

    def countify_expression(expression)
      expression + ".count"
    end
    
  end
  
end