diff --git a/lib/active_model_serializers/test/serializer.rb b/lib/active_model_serializers/test/serializer.rb
index 76b6c371b..8e8c95498 100644
--- a/lib/active_model_serializers/test/serializer.rb
+++ b/lib/active_model_serializers/test/serializer.rb
@@ -5,7 +5,6 @@ module Serializer
 
       included do
         setup :setup_serialization_subscriptions
-        teardown :teardown_serialization_subscriptions
       end
 
       # Asserts that the request was rendered with the appropriate serializers.
@@ -29,75 +28,94 @@ module Serializer
       #  assert_serializer nil
       #
       def assert_serializer(expectation, message = nil)
-        # Force body to be read in case the template is being streamed.
-        response.body
-
-        msg = message || "expecting <#{expectation.inspect}> but rendering with <#{serializers}>"
-
-        matches_serializer = case expectation
-                             when a_serializer?
-                               matches_class?(expectation)
-                             when Symbol
-                               matches_symbol?(expectation)
-                             when String
-                               matches_string?(expectation)
-                             when Regexp
-                               matches_regexp?(expectation)
-                             when NilClass
-                               matches_nil?
-                             else
-                               fail ArgumentError, 'assert_serializer only accepts a String, Symbol, Regexp, ActiveModel::Serializer, or nil'
-                             end
-        assert(matches_serializer, msg)
+        @assert_serializer.expectation = expectation
+        @assert_serializer.message = message
+        @assert_serializer.response = response
+        assert(@assert_serializer.matches?, @assert_serializer.message)
       end
 
-      private
+      class AssertSerializer
+        attr_reader :serializers, :message
+        attr_accessor :response, :expectation
 
-      ActiveModelSerializers.silence_warnings do
-        attr_reader :serializers, :expectation
-      end
+        def initialize
+          @serializers = []
+        end
 
-      def setup_serialization_subscriptions
-        @serializers = []
-        ActiveSupport::Notifications.subscribe(event_name) do |_name, _start, _finish, _id, payload|
-          serializer = payload[:serializer].name
-          serializers << serializer
+        def message=(message)
+          @message = message || "expecting <#{expectation.inspect}> but rendering with <#{serializers}>"
         end
-      end
 
-      def teardown_serialization_subscriptions
-        ActiveSupport::Notifications.unsubscribe(event_name)
-      end
+        def matches?
+          # Force body to be read in case the template is being streamed.
+          response.body
 
-      def event_name
-        'render.active_model_serializers'
-      end
+          case expectation
+          when a_serializer?
+            matches_class?
+          when Symbol
+            matches_symbol?
+          when String
+            matches_string?
+          when Regexp
+            matches_regexp?
+          when NilClass
+            matches_nil?
+          else
+            fail ArgumentError, 'assert_serializer only accepts a String, Symbol, Regexp, ActiveModel::Serializer, or nil'
+          end
+        end
 
-      def matches_class?(expectation)
-        serializers.include?(expectation.name)
-      end
+        def subscribe
+          ActiveSupport::Notifications.subscribe(event_name) do |_name, _start, _finish, _id, payload|
+            serializer = payload[:serializer].name
+            serializers << serializer
+          end
+        end
 
-      def matches_symbol?(expectation)
-        expectation = expectation.to_s.camelize
-        serializers.include?(expectation)
-      end
+        def unsubscribe
+          ActiveSupport::Notifications.unsubscribe(event_name)
+        end
 
-      def matches_string?(expectation)
-        !expectation.empty? && serializers.include?(expectation)
-      end
+        private
 
-      def matches_regexp?(expectation)
-        serializers.any? do |serializer|
-          serializer.match(expectation)
+        def matches_class?
+          serializers.include?(expectation.name)
         end
-      end
 
-      def matches_nil?
-        serializers.blank?
+        def matches_symbol?
+          camelize_expectation = expectation.to_s.camelize
+          serializers.include?(camelize_expectation)
+        end
+
+        def matches_string?
+          !expectation.empty? && serializers.include?(expectation)
+        end
+
+        def matches_regexp?
+          serializers.any? do |serializer|
+            serializer.match(expectation)
+          end
+        end
+
+        def matches_nil?
+          serializers.blank?
+        end
+
+        def a_serializer?
+          ->(exp) { exp.is_a?(Class) && exp < ActiveModel::Serializer }
+        end
+
+        def event_name
+          'render.active_model_serializers'
+        end
       end
 
-      def a_serializer?
-        ->(exp) { exp.is_a?(Class) && exp < ActiveModel::Serializer }
+      private
+
+      def setup_serialization_subscriptions
+        @assert_serializer = AssertSerializer.new
+        @assert_serializer.subscribe
       end
     end
   end