Module Test::Unit::Assertions
In: vendor/rails/activesupport/lib/active_support/core_ext/test/unit/assertions.rb

Methods

Public Instance methods

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 error message can be specified.

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

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/test/unit/assertions.rb, line 37
37:       def assert_difference(expressions, difference = 1, message = nil, &block)
38:         expression_evaluations = Array(expressions).collect{ |expression| lambda { eval(expression, block.send!(:binding)) } }
39: 
40:         original_values = expression_evaluations.inject([]) { |memo, expression| memo << expression.call }
41:         yield
42:         expression_evaluations.each_with_index do |expression, i|
43:           assert_equal original_values[i] + difference, expression.call, message
44:         end
45:       end

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 destroyed" do
    post :create, :article => invalid_attributes
  end

[Source]

    # File vendor/rails/activesupport/lib/active_support/core_ext/test/unit/assertions.rb, line 59
59:       def assert_no_difference(expressions, message = nil, &block)
60:         assert_difference expressions, 0, message, &block
61:       end

[Validate]