Add some model tests (#9)

Reviewed-on: #9

test/controllers/expenses_controller_test.rb

@@ -2,7 +2,7 @@ require "test_helper"
 
 class ExpensesControllerTest < ActionDispatch::IntegrationTest
   setup do
-    @expense = expenses(:one)
+    @expense = expenses(:monthly_expense)
   end
 
   test "should get index" do

test/controllers/incomes_controller_test.rb

@@ -2,7 +2,7 @@ require "test_helper"
 
 class IncomesControllerTest < ActionDispatch::IntegrationTest
   setup do
-    @income = incomes(:one)
+    @income = incomes(:included_1)
   end
 
   test "should get index" do