Refactor isolators into top-level classes

README.md

@@ -130,9 +130,9 @@ FixtureKit.configure do |config|
   # Where cache files are stored (default: tmp/cache/fixture_kit)
   config.cache_path = Rails.root.join("tmp/cache/fixture_kit").to_s
 
-  # Wrapper used to isolate generation work (default: FixtureKit::Minitest::Isolator)
-  # config.isolator = FixtureKit::Minitest::Isolator
-  # config.isolator = FixtureKit::RSpec::Isolator
+  # Wrapper used to isolate generation work (default: FixtureKit::MinitestIsolator)
+  # config.isolator = FixtureKit::MinitestIsolator
+  # config.isolator = FixtureKit::RSpecIsolator
 
   # Optional callback, called whenever a fixture cache is generated.
   # Receives the fixture name as a String.
@@ -143,9 +143,9 @@ end
 Custom isolators should subclass `FixtureKit::Isolator` and implement `#run`.
 `#run` receives the generation block and should execute it in whatever lifecycle you need.
 
-By default, FixtureKit uses `FixtureKit::Minitest::Isolator`, which runs generation inside an internal `ActiveSupport::TestCase` and removes that harness case from minitest runnables.
+By default, FixtureKit uses `FixtureKit::MinitestIsolator`, which runs generation inside an internal `ActiveSupport::TestCase` and removes that harness case from minitest runnables.
 
-When using `fixture_kit/rspec`, FixtureKit sets `FixtureKit::RSpec::Isolator`. It runs generation inside an internal RSpec example, and uses a null reporter so harness runs do not count toward suite example totals.
+When using `fixture_kit/rspec`, FixtureKit sets `FixtureKit::RSpecIsolator`. It runs generation inside an internal RSpec example, and uses a null reporter so harness runs do not count toward suite example totals.
 
 ## Lifecycle
 

lib/fixture_kit.rb

@@ -2,10 +2,8 @@
 
 module FixtureKit
   class Error < StandardError; end
-  class DuplicateFixtureError < Error; end
   class DuplicateNameError < Error; end
   class CacheMissingError < Error; end
-  class PregenerationError < Error; end
   class FixtureDefinitionNotFound < Error; end
   class ExposedRecordNotFound < Error; end
   class RunnerAlreadyStartedError < Error; end
@@ -22,7 +20,8 @@ class RunnerAlreadyStartedError < Error; end
   autoload :Cache,         File.expand_path("fixture_kit/cache", __dir__)
   autoload :Runner,        File.expand_path("fixture_kit/runner", __dir__)
   autoload :Isolator,      File.expand_path("fixture_kit/isolator", __dir__)
-  autoload :Minitest,      File.expand_path("fixture_kit/minitest", __dir__)
+  autoload :MinitestIsolator, File.expand_path("fixture_kit/isolators/minitest_isolator", __dir__)
+  autoload :RSpecIsolator, File.expand_path("fixture_kit/isolators/rspec_isolator", __dir__)
 
   extend Singleton
 end

lib/fixture_kit/cache.rb

@@ -39,7 +39,7 @@ def load
     end
 
     def save
-      configuration.isolator.run do
+      FixtureKit.runner.isolator.run do
         models = SqlSubscriber.capture do
           @definition.evaluate
         end

lib/fixture_kit/configuration.rb

@@ -10,7 +10,7 @@ class Configuration
     def initialize
       @fixture_path = nil
       @cache_path = nil
-      @isolator = FixtureKit::Minitest::Isolator
+      @isolator = FixtureKit::MinitestIsolator
       @on_cache = nil
     end
 

lib/fixture_kit/isolators/minitest_isolator.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require "active_support/test_case"
+require "active_record/fixtures"
+
+module FixtureKit
+  class MinitestIsolator < FixtureKit::Isolator
+    TEST_NAME = "fixture kit cache pregeneration"
+
+    def run(&block)
+      test_class = build_test_class
+      test_method = test_class.test(TEST_NAME) do
+        block.call
+        pass
+      end
+
+      result = test_class.new(test_method).run
+      return if result.passed?
+
+      raise result.failures.first.error
+    end
+
+    private
+
+    def build_test_class
+      Class.new(ActiveSupport::TestCase) do
+        ::Minitest::Runnable.runnables.delete(self)
+        include(::ActiveRecord::TestFixtures)
+      end
+    end
+  end
+end

lib/fixture_kit/isolators/rspec_isolator.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module FixtureKit
+  class RSpecIsolator < FixtureKit::Isolator
+    def run(&block)
+      previous_example = ::RSpec.current_example
+      previous_scope = ::RSpec.current_scope
+      example_group = build_example_group
+      example = example_group.example { block.call }
+      instance = example_group.new
+      succeeded =
+        begin
+          example.run(instance, ::RSpec::Core::NullReporter)
+        ensure
+          ::RSpec.current_example = previous_example
+          ::RSpec.current_scope = previous_scope
+        end
+
+      raise example.exception unless succeeded
+    end
+
+    private
+
+    def build_example_group
+      ::RSpec::Core::ExampleGroup.subclass(
+        ::RSpec::Core::ExampleGroup,
+        "FixtureKit",
+        [],
+        []
+      )
+    end
+  end
+end

lib/fixture_kit/minitest.rb

@@ -1,7 +1,3 @@
 # frozen_string_literal: true
 
-module FixtureKit
-  module Minitest
-    autoload :Isolator, File.expand_path("minitest/isolator", __dir__)
-  end
-end
+require "fixture_kit"

lib/fixture_kit/rspec.rb

@@ -4,8 +4,6 @@
 
 module FixtureKit
   module RSpec
-    autoload :Isolator, File.expand_path("rspec/isolator", __dir__)
-
     DECLARATION_METADATA_KEY = :fixture_kit_declaration
 
     # Class methods (extended via config.extend)
@@ -45,7 +43,7 @@ def fixture
 
     def self.configure!(config)
       config.add_setting(:fixture_kit, default: FixtureKit.runner)
-      FixtureKit.runner.configuration.isolator = Isolator
+      FixtureKit.runner.configuration.isolator = FixtureKit::RSpecIsolator
 
       config.extend ClassMethods
       config.include InstanceMethods, DECLARATION_METADATA_KEY

lib/fixture_kit/runner.rb

@@ -11,6 +11,7 @@ class Runner
     def initialize
       @configuration = Configuration.new
       @registry = Registry.new
+      @isolator = nil
       @started = false
     end
 
@@ -28,6 +29,10 @@ def start
       registry.fixtures.each(&:cache)
     end
 
+    def isolator
+      @isolator ||= configuration.isolator.new
+    end
+
     def started?
       @started
     end

spec/integration/dummy_app_spec.rb

@@ -6,6 +6,7 @@
   DUMMY_ROOT = File.expand_path("../dummy", __dir__)
   DUMMY_RSPEC_PATH = "spec/integration/fixture_kit_integration.rb"
   DUMMY_MINITEST_PATH = "test/integration/fixture_kit_integration_test.rb"
+  EXPECTED_DUMMY_TEST_COUNT = 8
   INTEGRATION_FRAMEWORK = ENV.fetch("FIXTURE_KIT_INTEGRATION_FRAMEWORK", "rspec")
 
   def run_dummy_tests
@@ -69,5 +70,14 @@ def run_dummy_tests
     expected_markers.each do |marker|
       expect(output).to include(marker), "Expected marker #{marker.inspect} in output.\nOutput:\n#{output}"
     end
+
+    case INTEGRATION_FRAMEWORK
+    when "rspec"
+      expect(output).to match(/\b#{EXPECTED_DUMMY_TEST_COUNT} examples, 0 failures\b/)
+    when "minitest"
+      expect(output).to match(/\b#{EXPECTED_DUMMY_TEST_COUNT} runs, \d+ assertions, 0 failures, 0 errors, \d+ skips\b/)
+    else
+      raise ArgumentError, "Unsupported integration framework: #{INTEGRATION_FRAMEWORK}"
+    end
   end
 end

spec/support/dummy_rails_helper.rb

@@ -101,5 +101,5 @@ def setup_databases
 FixtureKit.configure do |config|
   config.fixture_path = Rails.root.join("fixture_kit").to_s
   config.cache_path = Rails.root.join("tmp/cache/fixture_kit").to_s
-  config.isolator = FixtureKit::RSpec::Isolator if defined?(FixtureKit::RSpec::Isolator)
+  config.isolator = FixtureKit::RSpecIsolator if defined?(FixtureKit::RSpecIsolator)
 end

spec/unit/configuration_spec.rb

@@ -4,8 +4,8 @@
 
 RSpec.describe FixtureKit::Configuration do
   describe "#isolator" do
-    it "defaults to FixtureKit::Minitest::Isolator" do
-      expect(described_class.new.isolator).to eq(FixtureKit::Minitest::Isolator)
+    it "defaults to FixtureKit::MinitestIsolator" do
+      expect(described_class.new.isolator).to eq(FixtureKit::MinitestIsolator)
     end
 
     it "returns an explicitly configured class" do

spec/unit/fixture_cache_spec.rb

@@ -18,7 +18,7 @@
 
   let(:pass_through_isolator) do
     Class.new do
-      def self.run(&block)
+      def run(&block)
         block.call
       end
     end

spec/unit/fixture_runner_spec.rb

@@ -11,6 +11,22 @@
     allow(FixtureKit::Registry).to receive(:new).and_return(registry)
   end
 
+  describe "#isolator" do
+    it "instantiates the configured isolator once and memoizes it" do
+      runner = described_class.new
+      isolator_instance = instance_double(FixtureKit::MinitestIsolator)
+      isolator_class = class_double(FixtureKit::MinitestIsolator, new: isolator_instance)
+      runner.configuration.isolator = isolator_class
+
+      first_isolator = runner.isolator
+      second_isolator = runner.isolator
+
+      expect(first_isolator).to equal(isolator_instance)
+      expect(second_isolator).to equal(isolator_instance)
+      expect(isolator_class).to have_received(:new).once
+    end
+  end
+
   describe "#start" do
     it "clears all cache files before caching fixtures" do
       runner = described_class.new

spec/unit/minitest_isolator_spec.rb

@@ -2,7 +2,7 @@
 
 require "spec_helper"
 
-RSpec.describe FixtureKit::Minitest::Isolator do
+RSpec.describe FixtureKit::MinitestIsolator do
   describe ".run" do
     it "builds an ActiveSupport::TestCase harness" do
       captured_test_case_class = nil
@@ -17,7 +17,23 @@
       expect(captured_test_case_class).to be < ActiveSupport::TestCase
       expect(captured_test_case_class.included_modules).to include(ActiveRecord::TestFixtures)
       expect(captured_test_case_class.public_instance_methods(false).map(&:to_s))
-        .to include(described_class::TEST_METHOD_NAME)
+        .to include("test_fixture_kit_cache_pregeneration")
+    end
+
+    it "builds a fresh harness class for each run on the same isolator instance" do
+      captured_test_case_classes = []
+
+      allow(Minitest::Runnable.runnables).to receive(:delete).and_wrap_original do |original, test_case_class|
+        captured_test_case_classes << test_case_class
+        original.call(test_case_class)
+      end
+
+      isolator = described_class.new
+      isolator.run { nil }
+      isolator.run { nil }
+
+      expect(captured_test_case_classes.size).to be >= 2
+      expect(captured_test_case_classes[-2]).not_to equal(captured_test_case_classes[-1])
     end
 
     it "does not leak harness test cases into minitest runnables" do
@@ -40,16 +56,14 @@
       expect(Minitest::Runnable.runnables).to eq(runnables_before)
     end
 
-    it "raises FixtureKit::PregenerationError when run fails without a failure" do
-      isolator = described_class.new
-      result = instance_double(Minitest::Result, passed?: false, failures: [])
-      test_case = instance_double(ActiveSupport::TestCase, run: result)
-
-      allow(described_class).to receive(:new).and_return(isolator)
-      allow(isolator).to receive(:build_test_class).and_return(test_case)
+    it "re-raises the first failure error when run fails" do
+      failure_error = RuntimeError.new("harness exploded")
+      failure = instance_double(Minitest::UnexpectedError, error: failure_error)
+      result = instance_double(Minitest::Result, passed?: false, failures: [failure])
+      allow_any_instance_of(ActiveSupport::TestCase).to receive(:run).and_return(result)
 
       expect { described_class.run { nil } }
-        .to raise_error(FixtureKit::PregenerationError, "FixtureKit pregeneration failed")
+        .to raise_error(RuntimeError, "harness exploded")
     end
   end
 end