Module: Shoulda::ChangeMatchers

Defined in:
lib/shoulda/change_matchers.rb

Instance Method Summary collapse

Instance Method Details

#should_change(description, options = {}, &block) ⇒ Object

Macro that creates a test asserting a change between the return value of a block that is run before and after the current setup block is run. This is similar to Active Support’s assert_difference assertion, but supports more than just numeric values. See also should_not_change.

The passed description will be used when generating the test name and failure messages.

Example:

context "Creating a post" do
  setup { Post.create }
  should_change("the number of posts", :by => 1) { Post.count }
end

As shown in this example, the :by option expects a numeric difference between the before and after values of the expression. You may also specify :from and :to options:

should_change("the number of posts", :from => 0, :to => 1) { Post.count }
should_change("the post title", :from => "old", :to => "new") { @post.title }

Combinations of :by, :from, and :to are allowed:

# Assert the value changed in some way:
should_change("the post title") { @post.title }

# Assert the value changed to anything other than "old:"
should_change("the post title", :from => "old") { @post.title }

# Assert the value changed to "new:"
should_change("the post title", :to => "new") { @post.title }

This macro was deprecated because these tests aren’t as valuable as alternative tests that explicitly test the final state.

Consider an alternative:

context "updating a post" do
  setup do
    @post = Post.create(:title => "old")
    put :update, :post => {:title => "new"}, :id => @post.to_param
  end
  should "update the title" do
    assert_equal "new", @post.reload.title
  end
end



50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
 
# File 'lib/shoulda/change_matchers.rb', line 50

def should_change(description, options = {}, &block)
  by, from, to = shoulda_get_options!([options], :by, :from, :to)
  stmt = "change #{description}"
  stmt << " from #{from.inspect}" if from
  stmt << " to #{to.inspect}" if to
  stmt << " by #{by.inspect}" if by

  before = lambda { @_before_should_change = instance_eval(&block) }
  should stmt, :before => before do
    old_value = @_before_should_change
    new_value = instance_eval(&block)
    assert_operator from, :===, old_value, "#{description} did not originally match #{from.inspect}" if from
    assert_not_equal old_value, new_value, "#{description} did not change" unless by == 0
    assert_operator to, :===, new_value, "#{description} was not changed to match #{to.inspect}" if to
    assert_equal old_value + by, new_value if by
  end
end

#should_create(class_name) ⇒ Object

Deprecated.

Macro that creates a test asserting that a record of the given class was created.

Example:

context "creating a post" do
  setup { Post.create(post_attributes) }
  should_create :post
end



121
122
123
 
# File 'lib/shoulda/change_matchers.rb', line 121

def should_create(class_name)
  should_change_record_count_of(class_name, 1, 'create')
end

#should_destroy(class_name) ⇒ Object

Deprecated.

Macro that creates a test asserting that a record of the given class was destroyed.

Example:

context "destroying a post" do
  setup { Post.first.destroy }
  should_destroy :post
end



136
137
138
 
# File 'lib/shoulda/change_matchers.rb', line 136

def should_destroy(class_name)
  should_change_record_count_of(class_name, -1, 'destroy')
end

#should_not_change(description, &block) ⇒ Object

Deprecated.

Macro that creates a test asserting no change between the return value of a block that is run before and after the current setup block is run. This is the logical opposite of should_change.

The passed description will be used when generating the test name and failure message.

Example:

context "Updating a post" do
  setup { @post.update_attributes(:title => "new") }
  should_not_change("the number of posts") { Post.count }
end

This macro was deprecated because these tests aren’t as valuable as alternative tests that explicitly test the final state.

Consider an alternative:

context "updating a post" do
  setup do
    @post = Post.create(:title => "old")
    put :update, :post => {:title => ""}, :id => @post.to_param
  end
  should "not update the title" do
    assert_equal "old", @post.reload.title
  end
end



97
98
99
100
101
102
103
104
105
106
107
108
 
# File 'lib/shoulda/change_matchers.rb', line 97

def should_not_change(description, &block)
  before = lambda { @_before_should_not_change = instance_eval(&block) }
  should "not change #{description}", :before => before do
    new_value = instance_eval(&block)
    error_message = "#{description} changed"
    if @_before_should_not_change.nil?
      assert_nil new_value, error_message
    else
      assert_equal @_before_should_not_change, new_value, error_message
    end
  end
end