# module Rails::Dom::Testing::Assertions::SelectorAssertions

Adds the `assert_select` method for use in Rails functional test cases, which can be used to make assertions on the response HTML of a controller action. You can also call `assert_select` within another `assert_select` to make assertions on elements selected by the enclosing assertion.

Use `css_select` to select elements without making an assertions, either from the response HTML or elements selected by the enclosing assertion.

In addition to HTML responses, you can make the following assertions:

- `assert_select_encoded` - Assertions on HTML encoded inside XML, for example for dealing with feed item descriptions.

- `assert_select_email` - Assertions on the HTML body of an e-mail.

### Public Instance Methods

assert_select(*args, &block) click to toggle source

An assertion that selects elements and makes one or more equality tests.

If the first argument is an element, selects all matching elements starting from (and including) that element and all its children in depth-first order.

If no element is specified `assert_select` selects from the element returned in `document_root_element` unless `assert_select` is called from within an `assert_select` block. Override `document_root_element` to tell `assert_select` what to select from. The default implementation raises an exception explaining this.

When called with a block `assert_select` passes an array of selected elements to the block. Calling `assert_select` from the block, with no element specified, runs the assertion on the complete set of elements selected by the enclosing assertion. Alternatively the array may be iterated through so that `assert_select` can be called separately for each element.

#### Example¶ ↑

If the response contains two ordered lists, each with four list elements then:

    assert_select "ol" do |elements|
      elements.each do |element|
        assert_select element, "li", 4
      end
    end

will pass, as will:

    assert_select "ol" do
      assert_select "li", 8
    end

The selector may be a CSS selector expression (String) or an expression with substitution values (Array). Substitution uses a custom pseudo class match. Pass in whatever attribute you want to match (enclosed in quotes) and a ? for the substitution. #assert_select returns nil if called with an invalid css selector.

#assert_select “div:match('id', ?)”, /d+/

### Equality Tests¶ ↑

The equality test may be one of the following:

- `true` - Assertion is true if at least one element selected.

- `false` - Assertion is true if no element selected.

- `String/Regexp` - Assertion is true if the text value of at least one element matches the string or regular expression.

- `Integer` - Assertion is true if exactly that number of elements are selected.

- `Range` - Assertion is true if the number of selected elements fit the range.

If no equality test specified, the assertion is true if at least one element selected.

To perform more than one equality tests, use a hash with the following keys:

- `:text` - Narrow the selection to elements that have this text value (string or regexp).

- `:html` - Narrow the selection to elements that have this HTML content (string or regexp).

- `:count` - Assertion is true if the number of selected elements is equal to this value.

- `:minimum` - Assertion is true if the number of selected elements is at least this value.

- `:maximum` - Assertion is true if the number of selected elements is at most this value.

If the method is called with a block, once all equality tests are evaluated the block is called with an array of all matched elements.

    # At least one form element
    assert_select "form"

    # Form element includes four input fields
    assert_select "form input", 4

    # Page title is "Welcome"
    assert_select "title", "Welcome"

    # Page title is "Welcome" and there is only one title element
    assert_select "title", {count: 1, text: "Welcome"},
        "Wrong title or more than one title element"

    # Page contains no forms
    assert_select "form", false, "This page must contain no forms"

    # Test the content and style
    assert_select "body div.header ul.menu"

    # Use substitution values
    assert_select "ol>li:match('id', ?)", /item-\d+/

    # All input fields in the form have a name
    assert_select "form input" do
      assert_select ":match('name', ?)", /.+/  # Not empty
    end

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 161
    def assert_select(*args, &block)
      @selected ||= nil

      selector = HTMLSelector.new(args, @selected) { nodeset document_root_element }

      if selector.selecting_no_body?
        assert true
        return
      end

      selector.select.tap do |matches|
        assert_size_match!(matches.size, selector.tests,
          selector.css_selector, selector.message)

        nest_selection(matches, &block) if block_given? && !matches.empty?
      end
    end

assert_select_email(&block) click to toggle source

Extracts the body of an email and runs nested assertions on it.

You must enable deliveries for this assertion to work, use:

     ActionMailer::Base.perform_deliveries = true

    assert_select_email do
      assert_select "h1", "Email alert"
    end

    assert_select_email do
      items = assert_select "ol>li"
      items.each do
         # Work with items here...
      end
    end

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 247
    def assert_select_email(&block)
      deliveries = ActionMailer::Base.deliveries
      assert !deliveries.empty?, "No e-mail in delivery list"

      deliveries.each do |delivery|
        (delivery.parts.empty? ? [delivery] : delivery.parts).each do |part|
          if part["Content-Type"].to_s =~ /^text\/html\W/
            root = Nokogiri::HTML::DocumentFragment.parse(part.body.to_s)
            assert_select root, ":root", &block
          end
        end
      end
    end

assert_select_encoded(element = nil) { |selected| ... } click to toggle source

Extracts the content of an element, treats it as encoded HTML and runs nested assertion on it.

You typically call this method within another assertion to operate on all currently selected elements. You can also pass an element or array of elements.

The content of each element is un-encoded, and wrapped in the root element `encoded`. It then calls the block with all un-encoded elements.

    # Selects all bold tags from within the title of an Atom feed's entries (perhaps to nab a section name prefix)
    assert_select "feed[xmlns='http://www.w3.org/2005/Atom']" do
      # Select each entry item and then the title item
      assert_select "entry>title" do
        # Run assertions on the encoded title elements
        assert_select_encoded do
          assert_select "b"
        end
      end
    end

    # Selects all paragraph tags from within the description of an RSS feed
    assert_select "rss[version=2.0]" do
      # Select description element of each feed item.
      assert_select "channel>item>description" do
        # Run assertions on the encoded elements.
        assert_select_encoded do
          assert_select "p"
        end
      end
    end

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 211
    def assert_select_encoded(element = nil, &block)
      if !element && !@selected
        raise ArgumentError, "Element is required when called from a nonnested assert_select"
      end

      content = nodeset(element || @selected).map do |elem|
        elem.children.select do |child|
          child.cdata? || (child.text? && !child.blank?)
        end.map(&:content)
      end.join

      selected = Nokogiri::HTML::DocumentFragment.parse(content)
      nest_selection(selected) do
        if content.empty?
          yield selected
        else
          assert_select ":root", &block
        end
      end
    end

css_select(*args) click to toggle source

Select and return all matching elements.

If called with a single argument, uses that argument as a selector. Called without an element `css_select` selects from the element returned in `document_root_element`

The default implementation of `document_root_element` raises an exception explaining this.

Returns an empty Nokogiri::XML::NodeSet if no match is found.

If called with two arguments, uses the first argument as the root element and the second argument as the selector. Attempts to match the root element and any of its children. Returns an empty Nokogiri::XML::NodeSet if no match is found.

The selector may be a CSS selector expression (String). #css_select returns nil if called with an invalid css selector.

    # Selects all div tags
    divs = css_select("div")

    # Selects all paragraph tags and does something interesting
    pars = css_select("p")
    pars.each do |par|
      # Do something fun with paragraphs here...
    end

    # Selects all list items in unordered lists
    items = css_select("ul>li")

    # Selects all form tags and then all inputs inside the form
    forms = css_select("form")
    forms.each do |form|
      inputs = css_select(form, "input")
      ...
    end

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 59
    def css_select(*args)
      raise ArgumentError, "you at least need a selector argument" if args.empty?

      root = args.size == 1 ? document_root_element : args.shift

      nodeset(root).css(args.first)
    end

### Private Instance Methods

assert_size_match!(size, equals, css_selector, message = nil) click to toggle source

`equals` must contain :minimum, :maximum and :count keys

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 270
    def assert_size_match!(size, equals, css_selector, message = nil)
      min, max, count = equals[:minimum], equals[:maximum], equals[:count]

      message ||= %Q(Expected #{count_description(min, max, count)} matching "#{css_selector}", found #{size}.)
      if count
        assert_equal count, size, message
      else
        assert_operator size, :>=, min, message if min
        assert_operator size, :<=, max, message if max
      end
    end

document_root_element() click to toggle source

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 264
    def document_root_element
      raise NotImplementedError, 'Implementing document_root_element makes '                'assert_select work without needing to specify an element to select from.'
    end

nest_selection(selection) { |selected| ... } click to toggle source

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 282
    def nest_selection(selection)
      # Set @selected to allow nested assert_select.
      # Can be nested several levels deep.
      old_selected, @selected = @selected, selection
      yield @selected
    ensure
      @selected = old_selected
    end

nodeset(node) click to toggle source

    # File lib/rails/dom/testing/assertions/selector_assertions.rb, line 291
    def nodeset(node)
      if node.is_a?(Nokogiri::XML::NodeSet)
        node
      else
        Nokogiri::XML::NodeSet.new(node.document, [node])
      end
    end