Serialized users

app/controllers/api/v1/users_controller.rb

   before_action :check_owner, only: %i[update destroy]
 
   def index
-    render json: User.all
+    render json: UserSerializer.new(User.all).serializable_hash.to_json
   end
 
   def show
-    render json: User.find(params[:id])
+    render json: UserSerializer.new(@user).serializable_hash.to_json
   end
 
   def create
     @user = User.new(user_params)
 
     if @user.save
-      render json: @user, status: :created
+      render json: UserSerializer.new(@user).serializable_hash.to_json, status: :created
     else
       render json: @user.errors, status: :unprocessable_entity
     end
 
   def update
     if @user.update(user_params)
-      render json: @user, status: :ok
+      render json: UserSerializer.new(@user).serializable_hash.to_json, status: :ok
     else
       render json: @user.errors, status: :unprocessable_entity
     end

app/serializers/user_serializer.rb

+class UserSerializer
+  include JSONAPI::Serializer
+  attributes :email, :username
+end

test/controllers/api/v1/users_controller_test.rb

     assert_response :success
     # Test to ensure response contains the correct email
     json_response = JSON.parse(self.response.body)
-    assert_equal @user.email, json_response['email']
+    assert_equal @user.email, json_response['data']['attributes']['email']
   end
 
   #CREATE