Testing

tip

Our SDKs and Clients provide library and language-specific testing advice. For specific details, refer to the docs for the SDK or client you're using.

Testing is a first-class citizen in Prefab. We've designed it so that it is easy to test your code that uses Prefab.

Best Practices For Testing

The best practice for testing is to create a test environment and use a datafile. A datafile is a JSON snapshot of your configuration, which allows the Prefab client to boot up in a consistent state without talking to the Prefab server.

You can then use mocking to override specific values as-needed, when you are testing the behavior of a particular feature flag or config.

Mocking

Backend SDKs

The primary way to test Prefab is by mocking out calls to Prefab. Here are some examples:

Java

@Test
void testPrefab(){
  ConfigClient mockConfigClient = mock(ConfigClient.class);
  when(mockConfigClient.liveString("sample.string")).thenReturn(FixedValue.of("test value"));
  when(mockConfigClient.liveLong("sample.long")).thenReturn(FixedValue.of(123L));

  MyClass myClass = new MyClass(mock(ConfigClient.class));

  // test business logic

}

Ruby

class Job < Array
  def batches
    slice_size = Prefab.get('job.batch.size')
    each_slice(slice_size)
  end
end

RSpec.describe Job do
  describe '#batches' do
    it 'returns batches of jobs' do
      jobs = Job.new([1, 2, 3, 4, 5])
      expect(jobs.batches.map(&:size)).to eq([3, 2])
      allow(Prefab).to receive(:get).with('job.batch.size').and_return(2)
      expect(jobs.batches.map(&:size)).to eq([2, 2, 1])
    end
  end
end

Frontend Libraries

Rather than talking to the server, use setConfig or use a Provider manually with your test setup.

JavaScript

Don't call prefab.init. Instead, use setConfig to set up your scenario.

prefab.setConfig({
  turbo: true,
  defaultMediaCount: 3,
});

Read the full JavaScript testing docs.

React

Don't use the PrefabProvider. Instead, use the PrefabTestProvider and pass in a config object.

<PrefabTestProvider config={config}>
  <MyComponent />
</PrefabTestProvider>,

Read the full React testing docs.

Testing with DataFiles

Mocking out all of the Prefab calls can be tedious, so we've added a feature called DataFiles to Prefab.

Having your tests/CI reach out to Prefab to get the latest configuration is a viable approach, but for consistency & reproducibility, many of us prefer to have full control over the configuration used to run tests. Datafiles are perfect for this use case.