Feature flags testing in Ruby on Rails Applications (SplitIoClient)

Feature flags are a powerful tool in Ruby on Rails development that allow you to control the rollout of new features and experiments. However, testing feature flags effectively is crucial to ensure that they work as intended and do not introduce bugs or regressions into your application. In this post, we’ll discuss some best practices for testing feature flags in Ruby on Rails applications.

1. Unit Test Flag Conditions

Start by writing unit tests to verify that feature flags are evaluated correctly under different conditions. Test scenarios where the flag is enabled, disabled, or set to specific variations. Ensure that the application behaves as expected in each case and that feature flag logic does not interfere with other parts of your codebase.

# Example RSpec test for feature flag condition
describe 'FeatureFlagService' do
  it 'returns true when the feature flag is enabled' do
    allow(SplitIoClient).to receive(:split).with('your_feature_key').and_return(double(enabled?: true))
    expect(FeatureFlagService.enabled?('your_feature_key')).to be true
  end

  it 'returns false when the feature flag is disabled' do
    allow(SplitIoClient).to receive(:split).with('your_feature_key').and_return(double(enabled?: false))
    expect(FeatureFlagService.enabled?('your_feature_key')).to be false
  end
end

2. Integration Testing

Include feature flag testing in your integration tests to ensure that flag behavior is consistent across different components of your application. Test scenarios where feature flags interact with other features, controllers, or views to verify that they function correctly in a real-world context.

# Example RSpec feature flag integration test
feature 'FeatureFlag Integration', type: :feature do
  scenario 'User sees feature when flag is enabled' do
    allow(SplitIoClient).to receive(:split).with('your_feature_key').and_return(double(enabled?: true))
    visit '/'
    expect(page).to have_content 'Your feature content'
  end

  scenario 'User does not see feature when flag is disabled' do
    allow(SplitIoClient).to receive(:split).with('your_feature_key').and_return(double(enabled?: false))
    visit '/'
    expect(page).not_to have_content 'Your feature content'
  end
end

3. Test Edge Cases

Consider edge cases and boundary conditions when testing feature flags to ensure robustness and reliability. Test scenarios where feature flags are toggled rapidly, set to invalid values, or interact with other dynamic elements of your application. Anticipating edge cases helps uncover potential issues and ensures that your feature flags are resilient under different conditions.

4. Stub External Dependencies

Use test doubles or stubs to mock external dependencies such as Split.io or other feature flagging services. By stubbing external calls, you can control the behavior of feature flags during testing and isolate your tests from external dependencies, improving test speed and reliability.

5. Continuous Integration

Integrate feature flag testing into your continuous integration (CI) pipeline to automate testing and ensure consistent behavior across environments. Run automated tests for feature flags alongside other tests to detect regressions early and maintain code quality throughout the development lifecycle.

Conclusion Testing feature flags in Ruby on Rails applications is essential to ensure that they function as expected and do not introduce unintended behavior or regressions. By following best practices such as unit testing flag conditions, integration testing, testing edge cases, stubbing external dependencies, and incorporating testing into your CI pipeline, you can ensure robust and reliable feature flag functionality in your applications.

Happy testing!