Add ability to fetch number of tests a scenario would run

qa/qa/runtime/env.rb

@@ -9,6 +9,7 @@ module QA
       extend self
 
       attr_writer :personal_access_token, :admin_personal_access_token
+      attr_accessor :dry_run
 
       ENV_VARIABLES = Gitlab::QA::Runtime::Env::ENV_VARIABLES
 

qa/qa/scenario/bootable.rb

@@ -30,6 +30,13 @@ module QA
                   Runtime::Scenario.define(opt.name, value)
                 end
 
+                next
+              elsif opt.name == :count_examples_only
+                parser.on(opt.arg, opt.desc) do |value|
+                  QA::Runtime::Env.dry_run = true
+                  Runtime::Scenario.define(opt.name, value)
+                end
+
                 next
               end
 

qa/qa/scenario/shared_attributes.rb

@@ -13,6 +13,7 @@ module QA
         'Specify FEATURE_FLAGS as comma-separated flag=state pairs, e.g., "flag1=enabled,flag2=disabled"'
       attribute :parallel, '--parallel', 'Execute tests in parallel'
       attribute :loop, '--loop', 'Execute test repeatedly'
+      attribute :count_examples_only, '--count-examples-only', 'Return the number of examples without running them'
     end
   end
 end

qa/qa/scenario/template.rb

@@ -40,7 +40,8 @@ module QA
         ##
         # Perform before hooks, which are different for CE and EE
         #
-        Runtime::Release.perform_before_hooks
+
+        Runtime::Release.perform_before_hooks unless Runtime::Env.dry_run
 
         Runtime::Feature.enable(options[:enable_feature]) if options.key?(:enable_feature)
         Runtime::Feature.disable(options[:disable_feature]) if options.key?(:disable_feature) && (@feature_enabled = Runtime::Feature.enabled?(options[:disable_feature]))

qa/qa/specs/runner.rb

@@ -9,6 +9,7 @@ module QA
       attr_accessor :tty, :tags, :options
 
       DEFAULT_TEST_PATH_ARGS = ['--', File.expand_path('./features', __dir__)].freeze
+      DEFAULT_STD_ARGS = [$stderr, $stdout].freeze
 
       def initialize
         @tty = false
@@ -68,8 +69,15 @@ module QA
           ParallelRunner.run(args.flatten)
         elsif Runtime::Scenario.attributes[:loop]
           LoopRunner.run(args.flatten)
+        elsif Runtime::Scenario.attributes[:count_examples_only]
+          args.unshift('--dry-run')
+          out = StringIO.new
+          RSpec::Core::Runner.run(args.flatten, $stderr, out).tap do |status|
+            abort if status.nonzero?
+          end
+          $stdout.puts out.string.match(/(\d+) examples,/)[1]
         else
-          RSpec::Core::Runner.run(args.flatten, $stderr, $stdout).tap do |status|
+          RSpec::Core::Runner.run(args.flatten, *DEFAULT_STD_ARGS).tap do |status|
             abort if status.nonzero?
           end
         end

qa/spec/scenario/test/integration/github_spec.rb

@@ -2,7 +2,7 @@
 
 RSpec.describe QA::Scenario::Test::Integration::Github do
   describe '#perform' do
-    let(:env) { spy('Runtime::Env', knapsack?: false) }
+    let(:env) { spy('Runtime::Env', knapsack?: false, dry_run: false) }
 
     before do
       stub_const('QA::Runtime::Env', env)

qa/spec/spec_helper.rb

@@ -12,7 +12,7 @@ QaDeprecationToolkitEnv.configure!
 
 Knapsack::Adapters::RSpecAdapter.bind if QA::Runtime::Env.knapsack?
 
-QA::Runtime::Browser.configure!
+QA::Runtime::Browser.configure! unless QA::Runtime::Env.dry_run
 QA::Runtime::AllureReport.configure!
 QA::Runtime::Scenario.from_env(QA::Runtime::Env.runtime_scenario_attributes)
 

qa/spec/specs/runner_spec.rb

@@ -28,6 +28,26 @@ RSpec.describe QA::Specs::Runner do
       end
     end
 
+    context 'when count_examples_only is set as an option' do
+      let(:out) { StringIO.new }
+
+      before do
+        QA::Runtime::Scenario.define(:count_examples_only, true)
+        out.string = '22 examples,'
+        allow(StringIO).to receive(:new).and_return(out)
+      end
+
+      it 'sets the `--dry-run` flag' do
+        expect_rspec_runner_arguments(['--dry-run', '--tag', '~orchestrated', '--tag', '~transient', '--tag', '~geo', *described_class::DEFAULT_TEST_PATH_ARGS], [$stderr, anything])
+
+        subject.perform
+      end
+
+      after do
+        QA::Runtime::Scenario.attributes.delete(:count_examples_only)
+      end
+    end
+
     context 'when tags are set' do
       subject { described_class.new.tap { |runner| runner.tags = %i[orchestrated github] } }
 
@@ -158,10 +178,10 @@ RSpec.describe QA::Specs::Runner do
       end
     end
 
-    def expect_rspec_runner_arguments(arguments)
+    def expect_rspec_runner_arguments(arguments, std_arguments = described_class::DEFAULT_STD_ARGS)
       expect(RSpec::Core::Runner).to receive(:run)
-        .with(arguments, $stderr, $stdout)
-        .and_return(0)
+                                       .with(arguments, *std_arguments)
+                                       .and_return(0)
     end
   end
 end