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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.

Also see HTML::Selector to learn how to use selectors.

Methods
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R
Instance Public methods
assert_select(*args, &block)

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 if specified, calling assert_select selects from the response HTML unless assert_select is called from within an assert_select block.

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), an expression with substitution values, or an HTML::Selector object.

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#?", /item-\d+/

# All input fields in the form have a name
assert_select "form input" do
  assert_select "[name=?]", /.+/  # Not empty
end
# File actionpack/lib/action_dispatch/testing/assertions/selector.rb, line 184
def assert_select(*args, &block)
  # Start with optional element followed by mandatory selector.
  arg = args.shift
  @selected ||= nil

  if arg.is_a?(HTML::Node)
    # First argument is a node (tag or text, but also HTML root),
    # so we know what we're selecting from.
    root = arg
    arg = args.shift
  elsif arg == nil
    # This usually happens when passing a node/element that
    # happens to be nil.
    raise ArgumentError, "First argument is either selector or element to select, but nil found. Perhaps you called assert_select with an element that does not exist?"
  elsif @selected
    root = HTML::Node.new(nil)
    root.children.concat @selected
  else
    # Otherwise just operate on the response document.
    root = response_from_page
  end

  # First or second argument is the selector: string and we pass
  # all remaining arguments. Array and we pass the argument. Also
  # accepts selector itself.
  case arg
    when String
      selector = HTML::Selector.new(arg, args)
    when Array
      selector = HTML::Selector.new(*arg)
    when HTML::Selector
      selector = arg
    else raise ArgumentError, "Expecting a selector as the first argument"
  end

  # Next argument is used for equality tests.
  equals = {}
  case arg = args.shift
    when Hash
      equals = arg
    when String, Regexp
      equals[:text] = arg
    when Integer
      equals[:count] = arg
    when Range
      equals[:minimum] = arg.begin
      equals[:maximum] = arg.end
    when FalseClass
      equals[:count] = 0
    when NilClass, TrueClass
      equals[:minimum] = 1
    else raise ArgumentError, "I don't understand what you're trying to match"
  end

  # By default we're looking for at least one match.
  if equals[:count]
    equals[:minimum] = equals[:maximum] = equals[:count]
  else
    equals[:minimum] = 1 unless equals[:minimum]
  end

  # Last argument is the message we use if the assertion fails.
  message = args.shift
  #- message = "No match made with selector #{selector.inspect}" unless message
  if args.shift
    raise ArgumentError, "Not expecting that last argument, you either have too many arguments, or they're the wrong type"
  end

  matches = selector.select(root)
  # If text/html, narrow down to those elements that match it.
  content_mismatch = nil
  if match_with = equals[:text]
    matches.delete_if do |match|
      text = ""
      stack = match.children.reverse
      while node = stack.pop
        if node.tag?
          stack.concat node.children.reverse
        else
          content = node.content
          text << content
        end
      end
      text.strip! unless NO_STRIP.include?(match.name)
      text.sub!(/\A\n/, '') if match.name == "textarea"
      unless match_with.is_a?(Regexp) ? (text =~ match_with) : (text == match_with.to_s)
        content_mismatch ||= sprintf("<%s> expected but was\n<%s>", match_with, text)
        true
      end
    end
  elsif match_with = equals[:html]
    matches.delete_if do |match|
      html = match.children.map(&:to_s).join
      html.strip! unless NO_STRIP.include?(match.name)
      unless match_with.is_a?(Regexp) ? (html =~ match_with) : (html == match_with.to_s)
        content_mismatch ||= sprintf("<%s> expected but was\n<%s>", match_with, html)
        true
      end
    end
  end
  # Expecting foo found bar element only if found zero, not if
  # found one but expecting two.
  message ||= content_mismatch if matches.empty?
  # Test minimum/maximum occurrence.
  min, max, count = equals[:minimum], equals[:maximum], equals[:count]

  # FIXME: minitest provides messaging when we use assert_operator,
  # so is this custom message really needed?
  message = message || %Q(Expected #{count_description(min, max, count)} matching "#{selector.to_s}", found #{matches.size})
  if count
    assert_equal count, matches.size, message
  else
    assert_operator matches.size, :>=, min, message if min
    assert_operator matches.size, :<=, max, message if max
  end

  # If a block is given call that block. Set @selected to allow
  # nested assert_select, which can be nested several levels deep.
  if block_given? && !matches.empty?
    begin
      in_scope, @selected = @selected, matches
      yield matches
    ensure
      @selected = in_scope
    end
  end

  # Returns all matches elements.
  matches
end
assert_select_email(&block)

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 actionpack/lib/action_dispatch/testing/assertions/selector.rb, line 409
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 = HTML::Document.new(part.body.to_s).root
        assert_select root, ":root", &block
      end
    end
  end
end
assert_select_encoded(element = nil, &block)

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 actionpack/lib/action_dispatch/testing/assertions/selector.rb, line 361
def assert_select_encoded(element = nil, &block)
  case element
    when Array
      elements = element
    when HTML::Node
      elements = [element]
    when nil
      unless elements = @selected
        raise ArgumentError, "First argument is optional, but must be called from a nested assert_select"
      end
    else
      raise ArgumentError, "Argument is optional, and may be node or array of nodes"
  end

  fix_content = lambda do |node|
    # Gets around a bug in the Rails 1.1 HTML parser.
    node.content.gsub(/<!\[CDATA\[(.*)(\]\]>)?/m) { Rack::Utils.escapeHTML($1) }
  end

  selected = elements.map do |elem|
    text = elem.children.select{ |c| not c.tag? }.map{ |c| fix_content[c] }.join
    root = HTML::Document.new(CGI.unescapeHTML("<encoded>#{text}</encoded>")).root
    css_select(root, "encoded:root", &block)[0]
  end

  begin
    old_selected, @selected = @selected, selected
    assert_select ":root", &block
  ensure
    @selected = old_selected
  end
end
css_select(*args)

Select and return all matching elements.

If called with a single argument, uses that argument as a selector to match all elements of the current page. Returns an empty array if no match is found.

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

The selector may be a CSS selector expression (String), an expression with substitution values (Array) or an HTML::Selector object.

# 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 actionpack/lib/action_dispatch/testing/assertions/selector.rb, line 60
def css_select(*args)
  # See assert_select to understand what's going on here.
  arg = args.shift

  if arg.is_a?(HTML::Node)
    root = arg
    arg = args.shift
  elsif arg == nil
    raise ArgumentError, "First argument is either selector or element to select, but nil found. Perhaps you called assert_select with an element that does not exist?"
  elsif defined?(@selected) && @selected
    matches = []

    @selected.each do |selected|
      subset = css_select(selected, HTML::Selector.new(arg.dup, args.dup))
      subset.each do |match|
        matches << match unless matches.any? { |m| m.equal?(match) }
      end
    end

    return matches
  else
    root = response_from_page
  end

  case arg
    when String
      selector = HTML::Selector.new(arg, args)
    when Array
      selector = HTML::Selector.new(*arg)
    when HTML::Selector
      selector = arg
    else raise ArgumentError, "Expecting a selector as the first argument"
  end

  selector.select(root)
end
Instance Protected methods
response_from_page()

assert_select and css_select call this to obtain the content in the HTML page.

# File actionpack/lib/action_dispatch/testing/assertions/selector.rb, line 425
def response_from_page
  html_document.root
end