Provide natural mapping

.test-map.yml

@@ -3,6 +3,7 @@ lib/test_map/config.rb:
 - lib/test_map/config.rb
 - lib/test_map/file_recorder.rb
 - lib/test_map/filter.rb
+- lib/test_map/natural_mapping.rb
 lib/test_map/errors.rb:
 - lib/test_map/file_recorder.rb
 lib/test_map/file_recorder.rb:
@@ -11,19 +12,24 @@ lib/test_map/file_recorder.rb:
 - lib/test_map/file_recorder.rb
 - lib/test_map/filter.rb
 - lib/test_map/mapping.rb
+- lib/test_map/natural_mapping.rb
 - lib/test_map/plugins/minitest.rb
 - lib/test_map/report.rb
 lib/test_map/filter.rb:
 - lib/test_map/file_recorder.rb
 - lib/test_map/filter.rb
 lib/test_map/mapping.rb:
 - lib/test_map/mapping.rb
+lib/test_map/natural_mapping.rb:
+- lib/test_map/mapping.rb
+- lib/test_map/natural_mapping.rb
 lib/test_map/plugins/minitest.rb:
 - lib/test_map/config.rb
 - lib/test_map/errors.rb
 - lib/test_map/file_recorder.rb
 - lib/test_map/filter.rb
 - lib/test_map/mapping.rb
+- lib/test_map/natural_mapping.rb
 - lib/test_map/report.rb
 lib/test_map/report.rb:
 - lib/test_map/report.rb

README.md

@@ -27,6 +27,9 @@ TestMap::Configure.configure do |config|
   config.out_file = 'my-test-map.yml' # default is .test-map.yml
   # defaults to [%r{^(vendor|test|spec)/}] }
   config.exclude_patterns = [%r{^(libraries|testsuite)/}]
+  # register a custom rule to match new files; must implement `call(file)`;
+  # defaults to nil
+  config.natural_mapping = ->(file) { file.sub(%r{^library/}, 'test/') }
 end
 ```
 

lib/test_map.rb

@@ -6,6 +6,7 @@
 require_relative 'test_map/filter'
 require_relative 'test_map/report'
 require_relative 'test_map/file_recorder'
+require_relative 'test_map/natural_mapping'
 require_relative 'test_map/mapping'
 
 # TestMap records associated files to test execution.

lib/test_map/config.rb

@@ -11,7 +11,7 @@ def self.configure = yield(config)
 
     def self.default_config
       { logger: Logger.new('/dev/null'), out_file: '.test-map.yml',
-        exclude_patterns: [%r{^(vendor|test|spec)/}] }
+        exclude_patterns: [%r{^(vendor|test|spec)/}], natural_mapping: nil }
     end
   end
 end

lib/test_map/mapping.rb

@@ -9,20 +9,11 @@ def map = YAML.safe_load_file(map_file)
 
     def lookup(*changed_files)
       new_files = apply_natural_mapping(changed_files - map.keys)
-      map.values_at(*changed_files).flatten.compact.uniq.concat(new_files)
+      map.values_at(*changed_files).concat(new_files).flatten.compact.uniq
     end
 
     def apply_natural_mapping(files)
-      pattern = if File.exist?("#{Dir.pwd}/test")
-                  'test/%s_test.rb'
-                elsif File.exist?("#{Dir.pwd}/spec")
-                  'spec/%s_spec.rb'
-                # elseif Handle files in packs
-                else
-                  return [] # skip files
-                end
-
-      files.map { format(pattern, File.basename(_1, '.rb')) }
+      files.map { |file| NaturalMapping.new(file).test_files }
     end
   end
 end

lib/test_map/natural_mapping.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'yaml'
+
+module TestMap
+  # Natural mapping determines the test file for a given source file by
+  # applying common and configurable rules and transformation.
+  class NaturalMapping
+    CommonRule = Struct.new(:file) do
+      def self.call(file) = new(file).call
+
+      def call
+        if File.exist?('test')
+          transform('test')
+        elsif File.exist?('spec')
+          transform('spec')
+        end
+      end
+
+      def transform(type)
+        test_file = "#{File.basename(file, '.rb')}_#{type}.rb"
+        test_path = File.dirname(file).sub('app/', '')
+        test_path = nil if test_path == '.'
+        [type, test_path, test_file].compact.join('/')
+      end
+    end
+
+    attr_reader :file
+
+    def initialize(file) = @file = file
+    def test_files = Array(transform(file))
+
+    def transform(file)
+      self.class.registered_rules.each do |rule|
+        test_files = rule.call(file)
+
+        return test_files if test_files
+      end
+
+      nil
+    end
+
+    def self.registered_rules
+      @registered_rules ||= [
+        Config.config[:natural_mapping],
+        CommonRule
+      ].compact
+    end
+  end
+end

test/test_map/natural_mapping_test.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+# Tests for mapping.
+class NaturalMappingTest < Minitest::Test
+  def test_mapping
+    mapping = subject.new('lib/animal.rb')
+
+    assert_equal ['test/lib/animal_test.rb'], mapping.test_files
+  end
+
+  def test_rails_mapping
+    mapping = subject.new('app/model/animal.rb')
+
+    assert_equal ['test/model/animal_test.rb'], mapping.test_files
+  end
+
+  def test_specs
+    File.stub(:exist?, ->(type) { type == 'spec' }) do
+      mapping = subject.new('app/model/animal.rb')
+
+      assert_equal ['spec/model/animal_spec.rb'], mapping.test_files
+    end
+  end
+
+  def test_no_known_test_lib
+    File.stub(:exist?, ->(_) { false }) do
+      mapping = subject.new('lib/animal.rb')
+      puts mapping.test_files
+
+      assert_empty mapping.test_files
+    end
+  end
+
+  private
+
+  def subject = TestMap::NaturalMapping
+end