Split a big test file into multiple chunks and run them in parallel

Install

gem install parallel_split_test

Usage

1: prepare your databases

To use 1 database per test-process, add this to your config/database.yml

test:
  database: yourproject_test<%= ENV['TEST_ENV_NUMBER'] %>

• TEST_ENV_NUMBER is '' for the first process and 2 for the 2nd, it reuses your normal test database
• Optionally install parallel_tests to get database helper tasks like rake parallel:prepare

2: find a slow/big test file

# spec/xxx_spec.rb
require "spec_helper"

describe "X" do
  it {sleep 5}
  it {sleep 5}
  it {sleep 5}
end

3: run

parallel_split_test spec/xxx_spec.rb [regular test options]

Output

parallel_split_test spec/xx_spec.rb

Running examples in 2 processes
.

Finished in 5 seconds
1 example, 0 failures
..

Finished in 1 seconds
2 examples, 0 failures

Summary:
1 example, 0 failures
2 examples, 0 failures
Took 10.06 seconds with 2 processes

TIPS

• use -o/--out to get unified/clean output from all processes
• set number of processes to use with PARALLEL_SPLIT_TEST_PROCESSES environment variable
• unify JUnit output for rspec

before(:all) rspec hooks

The before(:all) hooks in rspec will be executed once for every process that runs a test in an example group. This means if you have more processes than tests in a group, the before(:all) block for that group will be fired N times. For example, this spec has 3 tests and a before(:all) block:

describe "before all behavior"
  before(:all) do
    puts "Process: #{Process.pid} Before ALL"
  end

  it "a" do
  end

  it "b" do
  end

  it "c" do
  end
end

When you run this with 3 or more processes you'll see the before(:all) call is invoked 3 times, once per each process (since "a", "b", and "c" tests are each run on a different process).

$ PARALLEL_SPLIT_TEST_PROCESSES=3 bundle exec parallel_split_test spec/ | grep "Before ALL"
Process: 31539 Before ALL
Process: 31538 Before ALL
Process: 31540 Before ALL

TODO

• Cucumber support
• Test::Unit / Minitest support

Authors

Contributors

• bootstraponline
• ModST

Michael Grosser
michael@grosser.it
License: MIT