```ruby
require "test_helper"

class SerializerFilterTest < Minitest::Test
  Filter = Knuckles::Pipeline::SerializerFilter

  def test_objects_are_wrapped_in_a_serializer
    serializer = Struct.new(:node)
    context = { serializer: serializer }
    output  = Filter.call([Object.new], context)

    assert_equal 1, output.length
    assert_instance_of serializer, output.first
  end
end
```

Add assertion around serializer in context
user
```ruby
require "test_helper"

class SerializerFilterTest < Minitest::Test
  Filter = Knuckles::Pipeline::SerializerFilter

  def test_objects_are_wrapped_in_a_serializer
    serializer = Struct.new(:node)
    context = { serializer: serializer }
    output = Filter.call([Object.new], context)

    assert_equal 1, output.length
    assert_instance_of serializer, output.first
  end

  def test_serializer_required_in_context
    assert_raises(KeyError) { Filter.call([], {}) }
  end
end
```
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