```ruby
require 'test_helper'

class HelperMethodsTest < ActionView::TestCase
  include Metamagic::HelperMethods

  test "meta tags generation" do
    meta title: "My Title",
         description: "My description.",
         keywords: ["One", "Two", "Three"]

    assert_equal %{<title>My Title</title>\n<meta content="My description." name="description" />\n<meta content="One, Two, Three" name="keywords" />}, metamagic
  end
end
```

Test not adding existing meta tags
user
```ruby
require 'test_helper'

class HelperMethodsTest < ActionView::TestCase
  include Metamagic::HelperMethods

  test "meta tags generation" do
    meta title: "My Title",
         description: "My description.",
         keywords: ["One", "Two", "Three"]

    assert_equal %{<title>My Title</title>\n<meta content="My description." name="description" />\n<meta content="One, Two, Three" name="keywords" />}, metamagic
  end

  test "not adding existing meta tags" do
    meta title: "Test Title",
         description: "Test description."

    meta title: "Second Title",
         description: "Second description."

    assert_equal %{<title>Test Title</title>\n<meta content="Test description." name="description" />}, metamagic
  end
end
```
assistant