assert_select(selector, equality?, message?)
assert_select(element, selector, equality?, message?)

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 will select from the response HTML. Calling #assert_select inside an #assert_select block will run the assertion for each element selected by the enclosing assertion.

Example

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

Or for short:

assert_select "ol>li" do
  assert_select "li"
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.

Examples

# 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

Source Code

# File action_controller/assertions/selector_assertions.rb, line 193
def assert_select(*args, &block)
  # Start with optional element followed by mandatory selector.
  arg = args.shift

  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_or_rjs
  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
          text << node.content
        end
      end
      text.strip! unless NO_STRIP.include?(match.name)
      unless match_with.is_a?(Regexp) ? (text =~ match_with) : (text == match_with.to_s)
        content_mismatch ||= build_message(message, "<?> expected but was\n<?>.", 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 ||= build_message(message, "<?> expected but was\n<?>.", 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 = equals[:minimum], equals[:maximum]
  message = message || %(Expected #{count_description(min, max)} matching "#{selector.to_s}", found #{matches.size}.)
  assert matches.size >= min, message if min
  assert matches.size <= max, message if max

  # 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