module ActiveSupport::Testing::Assertions - activesupport-4.2.3 Documentation

# module ActiveSupport::Testing::Assertions

### Public Instance Methods

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 ->{ Article.count }, 2 do
      post :create, article: {...}
    end

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

An 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 63
    def assert_difference(expression, difference = 1, message = nil, &block)
      expressions = Array(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

An 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 92
    def assert_no_difference(expression, message = nil, &block)
      assert_difference expression, 0, message, &block
    end

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

Assert that an expression is not truthy. Passes if `object` is `nil` or `false`. “Truthy” means “considered true in a conditional” like `if foo`.

    assert_not nil    # => true
    assert_not false  # => true
    assert_not 'foo'  # => Expected "foo" to be nil or false

An error message can be specified.

    assert_not foo, 'foo should be false'

    # File lib/active_support/testing/assertions.rb, line 17
    def assert_not(object, message = nil)
      message ||= "Expected #{mu_pp(object)} to be nil or false"
      assert !object, message
    end