# module ActiveSupport::Testing::Assertions

### Public Instance Methods

assert_blank(object, message=nil) click to toggle source

Test if an expression is blank. Passes if object.blank? is true.

    assert_blank [] # => true

    # File lib/active_support/testing/assertions.rb, line 83
    def assert_blank(object, message=nil)
      message ||= "#{object.inspect} is not blank"
      assert object.blank?, message
    end

assert_difference(expression, difference = 1, message = nil) { || ... } click to toggle source

Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block.

    assert_difference 'Article.count' do
      post :create, :article => {...}
    end

An arbitrary expression is passed in and evaluated.

    assert_difference 'assigns(:article).comments(:reload).size' do
      post :create, :comment => {...}
    end

An arbitrary positive or negative difference can be specified. The default is +1.

    assert_difference 'Article.count', -1 do
      post :delete, :id => ...
    end

An array of expressions can also be passed in and evaluated.

    assert_difference [ 'Article.count', 'Post.count' ], +2 do
      post :create, :article => {...}
    end

A lambda or a list of lambdas can be passed in and evaluated:

    assert_difference lambda { Article.count }, 2 do
      post :create, :article => {...}
    end

    assert_difference [->{ Article.count }, ->{ Post.count }], 2 do
      post :create, :article => {...}
    end

A error message can be specified.

    assert_difference 'Article.count', -1, "An Article should be destroyed" do
      post :delete, :id => ...
    end

    # File lib/active_support/testing/assertions.rb, line 47
    def assert_difference(expression, difference = 1, message = nil, &block)
      expressions = Array.wrap expression

      exps = expressions.map { |e|
        e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
      }
      before = exps.map { |e| e.call }

      yield

      expressions.zip(exps).each_with_index do |(code, e), i|
        error  = "#{code.inspect} didn't change by #{difference}"
        error  = "#{message}.\n#{error}" if message
        assert_equal(before[i] + difference, e.call, error)
      end
    end

assert_no_difference(expression, message = nil, &block) click to toggle source

Assertion that the numeric result of evaluating an expression is not changed before and after invoking the passed in block.

    assert_no_difference 'Article.count' do
      post :create, :article => invalid_attributes
    end

A error message can be specified.

    assert_no_difference 'Article.count', "An Article should not be created" do
      post :create, :article => invalid_attributes
    end

    # File lib/active_support/testing/assertions.rb, line 76
    def assert_no_difference(expression, message = nil, &block)
      assert_difference expression, 0, message, &block
    end

assert_present(object, message=nil) click to toggle source

Test if an expression is not blank. Passes if object.present? is true.

    assert_present {:data => 'x' } # => true

    # File lib/active_support/testing/assertions.rb, line 91
    def assert_present(object, message=nil)
      message ||= "#{object.inspect} is blank"
      assert object.present?, message
    end