What is factory_bot?

factory_bot is a tool for Ruby developers who need realistic test data when writing automated tests for their applications. Instead of manually creating sample users, orders, or other records every time you run a test, it lets you define reusable templates, called "factories", that generate that data automatically. Think of it as a way to set up convincing placeholder information so you can verify your code works without hand-crafting the same test data over and over. At its core, it works through a straightforward definition syntax where you describe what a typical object looks like. When a test runs, it asks for an instance, and the factory assembles it based on that template. It supports multiple build strategies, you can create fully saved database records, unsaved in-memory instances, plain attribute hashes, or stubbed objects that just pretend to exist. You can also define several factories for the same class, like having one factory for a regular user and another for an admin user, with inheritance to share common traits between them. This is aimed at developers and teams working on Ruby applications, especially those using Rails, who want their test suites to be maintainable and readable. For example, an e-commerce team might define factories for customers, products, and orders, then mix and match them to test checkout flows, discount logic, or inventory updates without writing repetitive setup code in every test file. The project has been around since 2008, originally created by Joe Ferris and maintained by the consultancy thoughtbot. It is a well-established part of the Ruby testing ecosystem. The README is fairly minimal, directing readers to separate documentation for getting started, but it does mention a companion project specifically for Rails integration and a community tool called FactoryTrace that helps identify unused factories and traits to keep your test suite clean.