FastRspec

One gem line. Your whole test stack. Every core.

Drop-in replacement for RSpec and Minitest (including Rails' ActiveSupport::TestCase), rebuilt lean: same API, a fraction of the overhead. Runs in parallel on all cores by default, and ships with batteries included and auto-configured: factories, Faker, VCR, WebMock, database cleaning, shoulda, time helpers, Capybara and coverage. Works with Rails and with plain Ruby. Runs on CRuby, JRuby and TruffleRuby.

Status: design phase (2026-10). Gem skeleton only, nothing is implemented yet. See docs/idea/.

Install

# Gemfile
group :development, :test do
  gem 'fast_rspec'
end

Then delete the gems it replaces:

- gem 'rspec'
- gem 'rspec-rails'
- gem 'factory_bot_rails'
- gem 'faker'
- gem 'vcr'
- gem 'webmock'
- gem 'database_cleaner-active_record'
- gem 'simplecov'
- gem 'minitest-reporters'
+ gem 'fast_rspec'

Run

Your commands stay the same:

bundle exec rspec          # all cores
bin/rails test             # all cores; `parallelize` is handled for you
bundle exec rake test      # plain Ruby + Minitest
bundle exec fast_rspec     # auto-detects RSpec / Minitest / both

You don't need to change any spec, test, spec_helper.rb, rails_helper.rb, test_helper.rb or test/support/** file. If you already configured something yourself, your configuration wins.

What's included

✅ = FastRspec's own lean implementation of the upstream API (zero runtime dependencies). 🔌 = keep the upstream gem in your Gemfile; FastRspec auto-configures it.

Battery	Same API as	Auto-configured
🧪 RSpec ✅	rspec-core, -expectations, -mocks, -rails	.rspec honoured, type inference on Rails
🧪 Minitest ✅	minitest 5 + 6, ActiveSupport::TestCase	parallelize routed to our pool
🏭 Factories ✅	factory_bot (+ rails)	definitions found, create/build included
🎲 Fake data ✅	faker	deterministic per --seed, unique reset per test
📼 HTTP ✅	vcr + webmock	cassettes in spec/cassettes or test/cassettes, real net blocked, localhost allowed
🧹 DB ✅	transactional tests + database_cleaner	per-worker DB, cloned from a template
🔍 Matchers 🔌	shoulda-matchers / -context	integrated with the framework in use
⏱️ Time 🔌	ActiveSupport TimeHelpers	included everywhere
🌐 System 🔌	capybara + cuprite	headless Chrome, unique port per worker
📊 Coverage ✅	simplecov	merged across workers (COVERAGE=1)
🔐 Auth / jobs 🔌	Devise, Sidekiq / Wurk, ActiveJob	test helpers, fake/inline modes, per-worker Redis DB

Turn any of them off:

FastRspec.configure { |c| c.batteries.disable :vcr, :capybara }

Parallelism

Ruby	How it runs
CRuby	boots once, forks N workers (copy-on-write), work-stealing queue, C extension on hot paths
JRuby / TruffleRuby	a real parallel thread pool (no GVL), using the pure-Ruby implementation

N is the number of cores by default. Use FAST_RSPEC_WORKERS=4 to change it, or -n 1 for a serial run. Each worker gets its own database, Redis DB, tmp dir and ports. When a test fails, you get a one-line command that reproduces it, including the seed and the worker's files.

Contributing

The gem lives in apps/fast-rspec/; the repository root holds the shared tooling (bin/, CI, docs, demos) — not an application server. Its contributor cycle is setup → tests → pre-PR checks:

./bin/setup
./bin/dev
./bin/check

Prerequisites and setup

• Bash, Ruby and Bundler, plus access to RubyGems to install the development bundle. The gem requires Ruby >= 3.2; mise.toml and apps/fast-rspec/.ruby-version both select Ruby 3.4.
• With mise installed, setup installs and selects the configured toolchain. Without mise, setup uses the Ruby already on PATH; provide a supported Ruby and Bundler yourself.
• CRuby needs a C compiler, make and Ruby development headers for the native extension. Setup's build-tool provisioning uses Debian/Ubuntu's dpkg and apt-get; if build-essential is missing, it requires passwordless sudo and package-repository access. This is not a portable OS provisioning script.

./bin/setup installs the bundle and compiles the native extension on CRuby. JRuby and TruffleRuby use the pure-Ruby path and skip that compilation step. Toolchain or dependency installation failures must be resolved before continuing.

./bin/dev runs bundle exec rake test, this gem's own development test suite, and then exits. It does not start a server or persistent services. ./bin/stop is an idempotent no-op; there is currently nothing at the root to stop.

Checks and packaging

Command	Stages
./bin/check	RuboCop lint, native compilation on CRuby, unit tests
./bin/check fast	RuboCop lint and unit tests; skips compilation
./bin/check full	Default stages, then upstream oracles and demo-app suites

There is no configured static typechecker. The gate returns nonzero if a stage fails. Full mode is not currently a green acceptance gate: the oracle task deliberately aborts with test:oracles: not implemented yet — see docs/idea/09-compat-oracles.md. Demo apps have their own dependencies and dual-stack harness; they are not a root development server.

For a build-plus-install smoke test, use:

./bin/rake smoke

That task builds the gem before invoking ./bin/gem-smoke, which installs it into a temporary gem home and requires it without Rails. Direct ./bin/gem-smoke needs an already-built apps/fast-rspec/pkg/fast_rspec-*.gem; it is not a standalone fresh-checkout gate.

Docs

• docs/idea/: design and roadmap
• AGENTS.md: conventions for contributors and AI agents
• llms.txt: one-file reference for coding agents (target contract; status per milestone)

License

MIT