Change assert_dom to scope with NodeSet

README.md

@@ -44,6 +44,11 @@ css_select '.hello' # => Nokogiri::XML::NodeSet of elements with hello class
 # select from a supplied node. assert_dom asserts elements exist.
 assert_dom document_root_element.at('.hello'), '.goodbye'
 
+# explicitly modifies the document_root_element for the supplied node and block
+assert_dom document_root_element.at('.hello') do
+  assert_dom 'p', 'Hello!'
+end
+
 # elements in CDATA encoded sections can also be selected
 assert_dom_encoded '#out-of-your-element'
 

lib/rails/dom/testing/assertions/selector_assertions.rb

@@ -160,6 +160,16 @@ def css_select(*args)
         #   assert_dom "form input" do
         #     assert_dom ":match('name', ?)", /.+/  # Not empty
         #   end
+        #
+        #   # move the document_root_element to a node
+        #   assert_dom document_root_element.at_css("main") do
+        #     assert_dom "h1", "Hello, World"
+        #   end
+        #
+        #   # move the document_root_element to a Nodeset
+        #   assert_dom css_select("section") do
+        #     assert_dom "h1"
+        #   end
         def assert_dom(*args, &block)
           @selected ||= nil
 
@@ -271,6 +281,10 @@ def document_root_element
               'assert_dom work without needing to specify an element to select from.'
           end
 
+          def current_root_element
+            @selected || document_root_element
+          end
+
           # +equals+ must contain :minimum, :maximum and :count keys
           def assert_size_match!(size, equals, css_selector, message = nil)
             min, max, count = equals[:minimum], equals[:maximum], equals[:count]

lib/rails/dom/testing/assertions/selector_assertions/html_selector.rb

@@ -6,8 +6,7 @@ class HTMLSelector #:nodoc:
 
   def initialize(values, previous_selection = nil, &root_fallback)
     @values = values
-    @root = extract_root(previous_selection, root_fallback)
-    extract_selectors
+    @root, @css_selector, @selector = extract_root_and_selectors(previous_selection, &root_fallback)
     @tests = extract_equality_tests
     @message = @values.shift
 
@@ -23,7 +22,16 @@ def selecting_no_body? #:nodoc:
   end
 
   def select
-    filter @root.css(@selector, context)
+    nodeset =
+      if @selector.present?
+        @root.css(@selector, context)
+      elsif @root.is_a? Nokogiri::XML::NodeSet
+        @root
+      else
+        Nokogiri::XML::NodeSet.new(@root.document, [@root])
+      end
+
+    filter nodeset
   end
 
   private
@@ -56,7 +64,7 @@ def filter(matches)
     Nokogiri::XML::NodeSet.new(matches.document, remaining)
   end
 
-  def extract_root(previous_selection, root_fallback)
+  def extract_root(previous_selection)
     possible_root = @values.first
 
     if possible_root == nil
@@ -68,20 +76,21 @@ def extract_root(previous_selection, root_fallback)
       possible_root
     elsif previous_selection
       previous_selection
-    else
-      root_fallback.call
     end
   end
 
-  def extract_selectors
-    selector = @values.shift
+  def extract_root_and_selectors(previous_selection, &root_fallback)
+    root = extract_root(previous_selection)
 
-    unless selector.is_a? String
-      raise ArgumentError, "Expecting a selector as the first argument"
-    end
+    if @values.first.is_a? String
+      selector = @values.shift
 
-    @css_selector = context.substitute!(selector, @values.dup, true)
-    @selector     = context.substitute!(selector, @values)
+      [ root || root_fallback.call, context.substitute!(selector, @values.dup, true),  context.substitute!(selector, @values) ]
+    elsif root.present?
+      [ root ]
+    else
+      raise ArgumentError, "Expecting a selector or node as the first argument"
+    end
   end
 
   def extract_equality_tests

test/selector_assertions_test.rb

@@ -199,6 +199,74 @@ def test_assert_select_text_match
     end
   end
 
+  def test_assert_dom_with_node
+    render_html <<~HTML
+      <aside>other</aside>
+      <div id="1">
+        <span>foo</span>
+      </div>
+      <div id="2">
+        <span>bar</span>
+      </div>
+    HTML
+    root = document_root_element.at_css("div")
+    assert_dom root do
+      assert_equal Nokogiri::XML::NodeSet.new(root.document, [root]), current_root_element
+      assert_dom "div", text: "foo", count: 1
+      assert_dom "span", text: "foo", count: 1
+      assert_dom "div", text: "bar", count: 0
+      assert_dom "span", text: "bar", count: 0
+      assert_dom "aside", text: "other", count: 0
+    end
+    assert_dom "div", text: "foo", count: 1
+    assert_dom "div", text: "bar", count: 1
+    assert_dom "aside", text: "other", count: 1
+  end
+
+  def test_assert_dom_with_nodeset
+    render_html <<~HTML
+      <aside>other</aside>
+      <div id="1">
+        <span>foo</span>
+      </div>
+      <div id="2">
+        <span>bar</span>
+      </div>
+    HTML
+
+    assert_dom css_select("div") do
+      assert_dom "div", text: "foo", count: 1
+      assert_dom "span", text: "foo", count: 1
+      assert_dom "div", text: "bar", count: 1
+      assert_dom "span", text: "bar", count: 1
+      assert_dom "aside", text: "other", count: 0
+    end
+    assert_dom "div", text: "foo", count: 1
+    assert_dom "div", text: "bar", count: 1
+    assert_dom "aside", text: "other", count: 1
+  end
+
+  def test_assert_dom_with_nodeset_and_options
+    render_html <<~HTML
+      <div>
+        <span>foo</span>
+      </div>
+      <div>
+        <span>bar</span>
+      </div>
+    HTML
+
+    assert_dom css_select("div"), count: 2
+    assert_dom css_select("div"), minimum: 1, maximum: 2
+
+    assert_raises Minitest::Assertion do
+      assert_dom css_select("div"), count: 1
+    end
+    assert_raises Minitest::Assertion do
+      assert_dom css_select("div"), minimum: 3
+    end
+  end
+
   #
   # Test css_select.
   #