Extract find_tests logic to ruby class + add specs

spec/tooling/lib/tooling/find_tests_spec.rb

+# frozen_string_literal: true
+
+require 'tempfile'
+require_relative '../../../../tooling/lib/tooling/find_tests'
+require_relative '../../../support/helpers/stub_env'
+
+RSpec.describe Tooling::FindTests, feature_category: :tooling do
+  include StubENV
+
+  attr_accessor :changes_file, :matching_tests_paths
+
+  let(:instance)                     { described_class.new(changes_file, matching_tests_paths) }
+  let(:mock_test_file_finder)        { instance_double(TestFileFinder::FileFinder) }
+  let(:new_matching_tests)           { ["new_matching_spec.rb"] }
+  let(:changes_file_content)         { "changed_file1 changed_file2" }
+  let(:matching_tests_paths_content) { "previously_matching_spec.rb" }
+
+  around do |example|
+    self.changes_file         = Tempfile.new('changes')
+    self.matching_tests_paths = Tempfile.new('matching_tests')
+
+    # See https://ruby-doc.org/stdlib-1.9.3/libdoc/tempfile/rdoc/
+    #     Tempfile.html#class-Tempfile-label-Explicit+close
+    begin
+      example.run
+    ensure
+      changes_file.close
+      matching_tests_paths.close
+      changes_file.unlink
+      matching_tests_paths.unlink
+    end
+  end
+
+  before do
+    allow(mock_test_file_finder).to receive(:use)
+    allow(mock_test_file_finder).to receive(:test_files).and_return(new_matching_tests)
+    allow(TestFileFinder::FileFinder).to receive(:new).and_return(mock_test_file_finder)
+
+    stub_env(
+      'RSPEC_TESTS_MAPPING_ENABLED' => nil,
+      'RSPEC_TESTS_MAPPING_PATH' => '/tmp/does-not-exist.out'
+    )
+
+    # We write into the temp files initially, to later check how the code modified those files
+    File.write(changes_file, changes_file_content)
+    File.write(matching_tests_paths, matching_tests_paths_content)
+  end
+
+  describe '#execute' do
+    subject { instance.execute }
+
+    context 'when the matching_tests_paths file does not exist' do
+      before do
+        allow(File).to receive(:exist?).and_return(false)
+        allow(File).to receive(:write).with(matching_tests_paths, any_args)
+      end
+
+      it 'creates an empty file' do
+        expect(File).to receive(:write).with(matching_tests_paths, '')
+
+        subject
+      end
+    end
+
+    context 'when the matching_tests_paths file already exists' do
+      it 'does not create an empty file' do
+        expect(File).not_to receive(:write).with(matching_tests_paths, '')
+
+        subject
+      end
+    end
+
+    it 'does not modify the content of the input file' do
+      expect { subject }.not_to change { File.read(changes_file) }
+    end
+
+    it 'does not overwrite the output file' do
+      expect { subject }.to change { File.read(matching_tests_paths) }
+                        .from(matching_tests_paths_content)
+                        .to("#{matching_tests_paths_content} #{new_matching_tests.uniq.join(' ')}")
+    end
+
+    it 'loads the tests.yml file with a pattern matching mapping' do
+      expect(TestFileFinder::MappingStrategies::PatternMatching).to receive(:load).with('tests.yml')
+
+      subject
+    end
+
+    context 'when RSPEC_TESTS_MAPPING_ENABLED env variable is set' do
+      before do
+        stub_env(
+          'RSPEC_TESTS_MAPPING_ENABLED' => 'true',
+          'RSPEC_TESTS_MAPPING_PATH' => 'crystalball-test/mapping.json'
+        )
+      end
+
+      it 'loads the direct matching pattern file' do
+        expect(TestFileFinder::MappingStrategies::DirectMatching)
+          .to receive(:load_json)
+          .with('crystalball-test/mapping.json')
+
+        subject
+      end
+    end
+
+    context 'when RSPEC_TESTS_MAPPING_ENABLED env variable is not set' do
+      let(:rspec_tests_mapping_enabled) { '' }
+
+      before do
+        stub_env(
+          'RSPEC_TESTS_MAPPING_ENABLED' => rspec_tests_mapping_enabled,
+          'RSPEC_TESTS_MAPPING_PATH' => rspec_tests_mapping_path
+        )
+      end
+
+      context 'when RSPEC_TESTS_MAPPING_PATH is set' do
+        let(:rspec_tests_mapping_path) { 'crystalball-test/mapping.json' }
+
+        it 'does not load the direct matching pattern file' do
+          expect(TestFileFinder::MappingStrategies::DirectMatching).not_to receive(:load_json)
+
+          subject
+        end
+      end
+
+      context 'when RSPEC_TESTS_MAPPING_PATH is not set' do
+        let(:rspec_tests_mapping_path) { nil }
+
+        it 'does not load the direct matching pattern file' do
+          expect(TestFileFinder::MappingStrategies::DirectMatching).not_to receive(:load_json)
+
+          subject
+        end
+      end
+    end
+
+    context 'when the same spec is matching multiple times' do
+      let(:new_matching_tests) do
+        [
+          "new_matching_spec.rb",
+          "duplicate_spec.rb",
+          "duplicate_spec.rb"
+        ]
+      end
+
+      it 'writes uniquely matching specs to the output' do
+        subject
+
+        expect(File.read(matching_tests_paths).split(' ')).to match_array(
+          matching_tests_paths_content.split(' ') + new_matching_tests.uniq
+        )
+      end
+    end
+  end
+end

tooling/bin/find_tests

 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-require 'test_file_finder'
+require_relative '../lib/tooling/find_tests'
 
-changes = ARGV.shift
-output_file = ARGV.shift
+changes_file         = ARGV.shift
+matching_tests_paths = ARGV.shift
 
-changed_files = File.read(changes).split(' ')
-
-tff = TestFileFinder::FileFinder.new(paths: changed_files).tap do |file_finder|
-  file_finder.use TestFileFinder::MappingStrategies::PatternMatching.load('tests.yml')
-
-  if ENV['RSPEC_TESTS_MAPPING_ENABLED']
-    file_finder.use TestFileFinder::MappingStrategies::DirectMatching.load_json(ENV['RSPEC_TESTS_MAPPING_PATH'])
-  end
-end
-
-File.write(output_file, tff.test_files.uniq.join(' '))
+Tooling::FindTests.new(changes_file, matching_tests_paths).execute

tooling/lib/tooling/find_tests.rb

+# frozen_string_literal: true
+
+require 'test_file_finder'
+
+module Tooling
+  class FindTests
+    def initialize(changes_file, matching_tests_paths)
+      @matching_tests_paths = matching_tests_paths
+      @changed_files        = File.read(changes_file).split(' ')
+
+      File.write(matching_tests_paths, '') unless File.exist?(matching_tests_paths)
+
+      @matching_tests = File.read(matching_tests_paths).split(' ')
+    end
+
+    def execute
+      tff = TestFileFinder::FileFinder.new(paths: changed_files).tap do |file_finder|
+        file_finder.use TestFileFinder::MappingStrategies::PatternMatching.load('tests.yml')
+
+        if ENV['RSPEC_TESTS_MAPPING_ENABLED'] == 'true'
+          file_finder.use TestFileFinder::MappingStrategies::DirectMatching.load_json(ENV['RSPEC_TESTS_MAPPING_PATH'])
+        end
+      end
+
+      new_matching_tests = tff.test_files.uniq
+      File.write(matching_tests_paths, (matching_tests + new_matching_tests).join(' '))
+    end
+
+    private
+
+    attr_reader :changed_files, :matching_tests, :matching_tests_paths
+  end
+end