FactoryBot::DuplicateDefinitionError: Factory already registered Ruby / Rails Origin: Application & API Last updated 5 Nov 2026

FactoryBot: FactoryBot::DuplicateDefinitionError: Factory already registered: user

Two factory definitions use the same name (or files are loaded twice).

Exact message you may see FactoryBot::DuplicateDefinitionError: Factory already registered: userFactory already registered: userFactoryGirl::DuplicateDefinitionError: Factory already registeredFactory already registered: admin_userDuplicateDefinitionError Factory already registered
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Seen on: Ruby

Meaning

Search for factory :user across spec/factories and test/factories. Duplicates arise from two files, copy/paste, or loading factories twice (FactoryBot.find_definitions plus factory_bot_rails auto-load). Rename one or merge them; use traits for variations.

Common causes

  • Same factory name defined in two files
  • Factories loaded twice (find_definitions + factory_bot_rails)
  • Gem engine providing the same factory
  • Copy-pasted file
  • Lint task loading twice

⚡ Quick fix

  1. grep -rn "factory :user" spec test and remove the duplicate
  2. Don't call FactoryBot.find_definitions manually if using factory_bot_rails
  3. Use traits instead of duplicate factories

Detailed fix by platform

Ruby

  1. grep -rn "factory :user" spec/ test/

How to diagnose

  1. Duplicates — Which files?
  2. Loading — Twice?
  3. Traits — Better?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Application & API. Errors that are often confused with or caused by this one (click to open):

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