Add assertions module (#6)

lib/dom_helpers.ex

@@ -10,6 +10,7 @@ defmodule DomHelpers do
   defmacro __using__(_opts) do
     quote do
       import DomHelpers.Accessors
+      import DomHelpers.Assertions
       import DomHelpers.Selectors
     end
   end

lib/dom_helpers/assertions.ex

@@ -0,0 +1,32 @@
+defmodule DomHelpers.Assertions do
+  @moduledoc """
+  This module contains some extra helpers specially for assertions,
+  though is preferred to use direct comparisons with the different
+  [selectors](`DomHelpers.Selectors`) and [accessors](`DomHelpers.Accessors`).
+  """
+
+  import DomHelpers.Accessors
+
+  @doc """
+  Checks if the given selector is found at least once
+  in the given document. Works like [`has_element?/2`](`Phoenix.LiveViewTest.has_element?/2`)
+  but with the parameters reversed so you can pipe when
+  building the selector.
+
+  ## Example
+
+  ```
+  iex> "li" |> is_in?("<ul><li>First</li><li>Second</li></ul>")
+  true
+
+  iex> "li" |> is_in?("<ul><li>First</li></ul>")
+  true
+
+  iex> "span" |> is_in?("<ul><li>First</li></ul>")
+  false
+  ```
+  """
+  def is_in?(selector, htmlable) do
+    find_count(htmlable, selector) > 0
+  end
+end

test/dom_helpers/assetions_test.exs

@@ -0,0 +1,8 @@
+defmodule DomHelpers.AssertionsTest do
+  @moduledoc false
+  use DomHelpers.Case
+
+  import DomHelpers.Assertions
+
+  doctest DomHelpers.Assertions
+end