gitlab-org--gitlab-foss/spec/experiments/application_experiment_spec.rb

# frozen_string_literal: true

require 'spec_helper'

RSpec.describe ApplicationExperiment, :experiment do
  subject { described_class.new('namespaced/stub') }

  let(:feature_definition) do
    { name: 'namespaced_stub', type: 'experiment', group: 'group::adoption', default_enabled: false }
  end

  around do |example|
    Feature::Definition.definitions[:namespaced_stub] = Feature::Definition.new('namespaced_stub.yml', feature_definition)
    example.run
    Feature::Definition.definitions.delete(:namespaced_stub)
  end

  before do
    allow(subject).to receive(:enabled?).and_return(true)
  end

  it "naively assumes a 1x1 relationship to feature flags for tests" do
    expect(Feature).to receive(:persist_used!).with('namespaced_stub')

    described_class.new('namespaced/stub')
  end

  it "doesn't raise an exception without a defined control" do
    # because we have a default behavior defined

    expect { experiment('namespaced/stub') { } }.not_to raise_error
  end

  describe "enabled" do
    before do
      allow(subject).to receive(:enabled?).and_call_original

      allow(Feature::Definition).to receive(:get).and_return('_instance_')
      allow(Gitlab).to receive(:dev_env_or_com?).and_return(true)
      allow(Feature).to receive(:get).and_return(double(state: :on))
    end

    it "is enabled when all criteria are met" do
      expect(subject).to be_enabled
    end

    it "isn't enabled if the feature definition doesn't exist" do
      expect(Feature::Definition).to receive(:get).with('namespaced_stub').and_return(nil)

      expect(subject).not_to be_enabled
    end

    it "isn't enabled if we're not in dev or dotcom environments" do
      expect(Gitlab).to receive(:dev_env_or_com?).and_return(false)

      expect(subject).not_to be_enabled
    end

    it "isn't enabled if the feature flag state is :off" do
      expect(Feature).to receive(:get).with('namespaced_stub').and_return(double(state: :off))

      expect(subject).not_to be_enabled
    end
  end

  describe "publishing results" do
    it "doesn't record, track or push data to the client if we shouldn't track", :snowplow do
      allow(subject).to receive(:should_track?).and_return(false)
      subject.record!

      expect(subject).not_to receive(:record_experiment)
      expect(subject).not_to receive(:track)
      expect(Gon).not_to receive(:push)

      subject.publish(:action)

      expect_no_snowplow_event
    end

    describe 'recording the experiment' do
      it 'does not record the experiment if we do not tell it to' do
        expect(subject).not_to receive(:record_experiment)

        subject.publish
      end

      it 'records the experiment if we tell it to' do
        subject.record!

        expect(subject).to receive(:record_experiment)

        subject.publish
      end
    end

    it "tracks the assignment" do
      expect(subject).to receive(:track).with(:assignment)

      subject.publish
    end

    it "pushes the experiment knowledge into the client using Gon" do
      expect(Gon).to receive(:push).with({ experiment: { 'namespaced/stub' => subject.signature } }, true)

      subject.publish
    end

    it "handles when Gon raises exceptions (like when it can't be pushed into)" do
      expect(Gon).to receive(:push).and_raise(NoMethodError)

      expect { subject.publish }.not_to raise_error
    end
  end

  it "can exclude from within the block" do
    expect(described_class.new('namespaced/stub') { |e| e.exclude! }).to be_excluded
  end

  describe 'recording the experiment subject' do
    using RSpec::Parameterized::TableSyntax

    subject { described_class.new('namespaced/stub', nil, **context) }

    before do
      subject.record!
    end

    context 'when providing a compatible context' do
      where(:context_key, :object_type) do
        :namespace | :group
        :group     | :group
        :project   | :project
        :user      | :user
        :actor     | :user
      end

      with_them do
        let(:context) { { context_key => build(object_type) }}

        it 'records the experiment and the experiment subject from the context' do
          expect { subject.publish }.to change(Experiment, :count).by(1)

          expect(Experiment.last.name).to eq('namespaced/stub')
          expect(ExperimentSubject.last.send(object_type)).to eq(context[context_key])
        end
      end
    end

    context 'when providing an incompatible or no context' do
      where(context_hash: [{ foo: :bar }, {}])

      with_them do
        let(:context) { context_hash }

        it 'does not record the experiment' do
          expect { subject.publish }.not_to change(Experiment, :count)
        end
      end
    end
  end

  describe "tracking events", :snowplow do
    it "doesn't track if we shouldn't track" do
      allow(subject).to receive(:should_track?).and_return(false)

      subject.track(:action)

      expect_no_snowplow_event
    end

    it "tracks the event with the expected arguments and merged contexts" do
      subject.track(:action, property: '_property_', context: [
        SnowplowTracker::SelfDescribingJson.new('iglu:com.gitlab/fake/jsonschema/0-0-0', { data: '_data_' })
      ])

      expect_snowplow_event(
        category: 'namespaced/stub',
        action: 'action',
        property: '_property_',
        context: [
          {
            schema: 'iglu:com.gitlab/fake/jsonschema/0-0-0',
            data: { data: '_data_' }
          },
          {
            schema: 'iglu:com.gitlab/gitlab_experiment/jsonschema/1-0-0',
            data: { experiment: 'namespaced/stub', key: '86208ac54ca798e11f127e8b23ec396a', variant: 'control' }
          }
        ]
      )
    end
  end

  describe "variant resolution" do
    it "uses the default value as specified in the yaml" do
      expect(Feature).to receive(:enabled?).with('namespaced_stub', subject, type: :experiment, default_enabled: :yaml)

      expect(subject.variant.name).to eq('control')
    end

    context "when rolled out to 100%" do
      before do
        stub_feature_flags(namespaced_stub: true)
      end

      it "returns the first variant name" do
        subject.try(:variant1) {}
        subject.try(:variant2) {}

        expect(subject.variant.name).to eq('variant1')
      end
    end
  end

  context "when caching" do
    let(:cache) { Gitlab::Experiment::Configuration.cache }

    before do
      allow(Gitlab::Experiment::Configuration).to receive(:cache).and_call_original

      cache.clear(key: subject.name)

      subject.use { } # setup the control
      subject.try { } # setup the candidate
    end

    it "caches the variant determined by the variant resolver" do
      expect(subject.variant.name).to eq('candidate') # we should be in the experiment

      subject.run

      expect(subject.cache.read).to eq('candidate')
    end

    it "doesn't cache a variant if we don't explicitly provide one" do
      # by not caching "empty" variants, we effectively create a mostly
      # optimal combination of caching and rollout flexibility. If we cached
      # every control variant assigned, we'd inflate the cache size and
      # wouldn't be able to roll out to subjects that we'd already assigned to
      # the control.
      stub_feature_flags(namespaced_stub: false) # simulate being not rolled out

      expect(subject.variant.name).to eq('control') # if we ask, it should be control

      subject.run

      expect(subject.cache.read).to be_nil
    end

    it "caches a control variant if we assign it specifically" do
      # by specifically assigning the control variant here, we're guaranteeing
      # that this context will always get the control variant unless we delete
      # the field from the cache (or clear the entire experiment cache) -- or
      # write code that would specify a different variant.
      subject.run(:control)

      expect(subject.cache.read).to eq('control')
    end

    context "arbitrary attributes" do
      before do
        subject.cache.store.clear(key: subject.name + '_attrs')
      end

      it "sets and gets attributes about an experiment" do
        subject.cache.attr_set(:foo, :bar)

        expect(subject.cache.attr_get(:foo)).to eq('bar')
      end

      it "increments a value for an experiment" do
        expect(subject.cache.attr_get(:foo)).to be_nil

        expect(subject.cache.attr_inc(:foo)).to eq(1)
        expect(subject.cache.attr_inc(:foo)).to eq(2)
      end
    end
  end
end