README

Run tests serially:

bin/rspec

This works: ✅

---

Run tests in parallel:

bin/rails parallel:spec

This works: ✅

---

Create the parallel test databases:

RAILS_ENV=test bin/rails parallel:create

This works ✅

---

Create the parallel test database without setting RAILS_ENV=test:

bin/rails parallel:create

This fails ❌:

(Note: I picked JWT very randomly as the example here. The problem isn't to do with JWT in particular).

$ rails parallel:create
bin/rails aborted!
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
bin/rails aborted!
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)
bin/rails aborted!
NameError: uninitialized constant JWT (NameError)

  puts JWT
       ^^^
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/initializers/jwt.rb:3:in '<top (required)>'
/Users/mjacobson/src/gh/maxjacobson/parallelagram/config/environment.rb:5:in '<top (required)>'
Tasks: TOP => db:create => db:load_config => environment
(See full trace by running task with --trace)

What seems to be happening:

• I run bin/rails parallel:create without setting RAILS_ENV
• Rails defaults to the development environment
• Bundler loads all of the gems in the development group of Gemfile
• dotenv-rails loads all of the environment variables in .env.development and exports them
• all of the rails initializers run without issue
• parallel_tests creates N subprocesses to create N databases. Each of those subproceses inherits the parent environment, which includes the variables defined in .env.development
• The subprocesses run with RAILS_ENV=test set, and so
  • Bundler loads all of the gems in the test group of Gemfile
  • dotenv loads the variables defined in .env.test. But it will not overwrite any value which is already in the environment, and so it does not overwrite ENABLE_COOL_FEATURE=true with the ENABLE_COOL_FEATURE=false value in .env.test
  • The subprocesses proceed to run all of the Rails initializers, and the error occurs because ENABLE_COOL_FEATURE=true and yet JWT is not loaded

Remediations available to me:

1. make that gem available in the development group too, so it's safe to run that initializer when creating parallel databases
2. Always export RAILS_ENV=test before running bin/rails parallel:create

It would be nice if it Just Worked though.