Cucumber Split

Cucumber Split is a Cucumber-JVM plugin that lets you toggle Split feature flags on or off using Cucumber tags.

Motivation

Software teams that use Split feature flags need to test that the software works as expected for different combinations of feature flags.

With Cucumber Split you can toggle feature flags declaratively with tags, and then verify that the software works as expected.

Example

Imagine we're building firmware for a coffee machine, and that we can deploy the new firmware over the Internet with continuous deployment.

The coffee machine is currently able to serve espresso, and caffe latte, and the team is currently working on an experimental new feature to serve flat white as well.

We have decided to make the new flat white drink available to a small set of customers, so we have introduced a feature flag to control whether it is available or not.

Even though only a small set of customers will have the flat white functionality, we want to test that it works as expected. We have two scenarios that verify options in the drink selection menu; One where flat white is not available (the feature flag is off), and another where it is (the feature flag is on):

Feature: Make Coffee

  @split[flat-white:off]
  Scenario: Display available drinks
    Given the machine is not empty
    Then the following drinks should be available:
      | name          | price |
      | espresso      |  1.90 |
      | caffe latte   |  2.30 |

  @split[flat-white:on]
  Scenario: Display available drinks (including the new experimental flat white)
    Given the machine is not empty
    Then the following drinks should be available:
      | name          | price |
      | espresso      |  1.90 |
      | flat white    |  2.10 |
      | caffe latte   |  2.30 |

Installation

First, add Cucumber Split to your project:

<!-- pom.xml -->
<dependency>
    <groupId>io.cucumber</groupId>
    <artifactId>cucumber-split</artifactId>
    <version>0.0.2</version>
    <scope>test</scope>
</dependency>

// build.gradle(.kts)
dependencies {
  testImplementation 'io.cucumber:cucumber-split:0.0.2'
}

Next, configure Cucumber to toggle Split features based on tags. Define a before hook:

import io.cucumber.java.Before;
import io.cucumber.java.Scenario;
import io.cucumber.split.CucumberSplit;
import io.split.client.testing.SplitClientForTest;

public class StepDefinitions {
    private final SplitClientForTest splitClient = new SplitClientForTest();

    @Before
    public void configureSplit(Scenario scenario) {
        CucumberSplit.configureSplit(splitClient, scenario);
    }
}

The configureSplit before hook will run before each scenario and configure the splitClient with feature flags declared as scenario tags.

Production code design

Your production code must be designed in such a way that a io.split.client.SplitClient can be passed to it, rather than creating its own instance. This is so that we can pass it the splitClient instantiated and configured by Cucumber.

One way to achieve this is with the dependency injection pattern.

In the example, the CoffeeMachine class expects a splitClient to be passed via its constructor.

Default feature flags

You may have some flags that you want to set by default, only to override them in certain scenarios. One way to achieve this is via Cucumber's tag inheritance:

# Turn flat white off by default
@split[flat-white:off]
Feature: Make Coffee

  Scenario: Display available drinks

  # Override flat white to on just in this scenario
  @split[flat-white:on]
  Scenario: Display available drinks (including the new experimental flat white)

Suggestions, questions or feedback

Please use the issue tracker if you have suggestions, questions or feedback about this library.