Karafka Testing library

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Karafka-Testing is a library that provides rspec helpers, to make testing of Karafka consumers much easier.


Add this gem to your Gemfile in the test group:

group :test do
  gem 'karafka-testing'
  gem 'rspec'

and then in your spec_helper.rb file:

require 'karafka/testing/rspec/helpers'

RSpec.configure do |config|
  config.include Karafka::Testing::RSpec::Helpers


Once included into your RSpec setup, this library will provide you two methods that you can use with your specs:

  • #karafka_consumer_for - this method will create a consumer instance for the desired topic. It needs to be set as the spec subject.
  • #publish_for_karafka - this method will "send" message to the consumer instance.

Note: Messages sent using the #publish_for_karafka method won't be sent to Kafka. They will be "virtually" delegated to the created consumer instance so your specs can run without Kafka setup.

RSpec.describe InlineBatchConsumer do
  # This will create a consumer instance with all the settings defined for the given topic
  subject(:consumer) { karafka_consumer_for(:inline_batch_data) }

  let(:nr1_value) { rand }
  let(:nr2_value) { rand }
  let(:sum) { nr1_value + nr2_value }

  before do
    # Sends first message to Karafka consumer
    publish_for_karafka({ 'number' => nr1_value }.to_json)    # Sends second message to Karafka consumer

    publish_for_karafka({ 'number' => nr2_value }.to_json)
    allow(Karafka.logger).to receive(:info)

  it 'expects to log a proper message' do
    expect(Karafka.logger).to receive(:info).with("Sum of 2 elements equals to: #{sum}")


Note on contributions

First, thank you for considering contributing to Karafka Testing! It's people like you that make the open source community such a great community!

Each pull request must pass all the RSpec specs and meet our quality requirements.

To check if everything is as it should be, we use Coditsu that combines multiple linters and code analyzers for both code and documentation. Once you're done with your changes, submit a pull request.

Coditsu will automatically check your work against our quality standards. You can find your commit check results on the builds page of the Karafka Testing repository.