Add basic CMAB DecisionService spec

Author: jaeopt

spec/cmab_service_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+require 'optimizely/decision_service'
+require 'optimizely/logger'
+
+describe 'CMAB DecisionService' do
+  let(:logger) { Optimizely::SimpleLogger.new }
+  let(:decision_service) { Optimizely::DecisionService.new(logger) }
+  let(:experiment) do
+    {
+      'id' => '12345',
+      'key' => 'cmab_experiment',
+      'type' => 'cmab',
+      'variations' => [
+        { 'id' => 'v1', 'key' => 'variation_1' },
+        { 'id' => 'v2', 'key' => 'variation_2' }
+      ]
+    }
+  end
+  let(:project_config) { double('ProjectConfig', get_experiment_from_id: experiment) }
+  let(:user_context) { double('UserContext', user_id: 'user_abc', user_attributes: {}) }
+
+  it 'returns a CMAB variation for a CMAB experiment' do
+    variation_id, reasons = decision_service.get_variation(project_config, '12345', user_context)
+    expect(['v1', 'v2']).to include(variation_id)
+    expect(reasons.any? { |r| r.include?('CMAB decision') }).to be true
+  end
+end