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Testing Async Module Implementation in concurrent-ruby

This test suite validates the Concurrent::Async module in Ruby, focusing on asynchronous method execution and concurrent programming patterns. It ensures proper handling of async/await operations, method delegation, and thread-safe execution in concurrent Ruby applications.

Test Coverage Overview

The test suite provides comprehensive coverage of the Concurrent::Async module’s core functionality.

Key areas tested include:

Object creation and constructor delegation
Argument validation and method arity checking
Async and await method execution patterns
Error handling and exception propagation
Thread safety and locking mechanisms
Fork safety verification

Implementation Analysis

The testing approach utilizes RSpec’s behavior-driven development framework with extensive use of context blocks and shared examples.

Notable patterns include:

Dynamic class creation for isolation testing
Mock object verification for executor interactions
Concurrent execution validation
IVar status checking for async operations

Technical Details

Testing infrastructure includes:

RSpec testing framework
Concurrent Ruby’s global IO executor
IVar implementation for future handling
Process forking tests for Unix platforms
Sleep-based timing verification

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices for concurrent code.

Notable practices include:

Isolated test contexts
Comprehensive edge case coverage
Proper async operation verification
Thread-safety validation
Platform-specific test conditioning

ruby-concurrency/concurrent-ruby

spec/concurrent/async_spec.rb

            
require 'concurrent/async'

module Concurrent
  RSpec.describe Async do

    let(:async_class) do
      Class.new do
        include Concurrent::Async
        attr_accessor :accessor
        def initialize(*args)
        end
        def echo(msg)
          msg
        end
        def gather(first, second = nil)
          return first, second
        end
        def boom(ex = StandardError.new)
          raise ex
        end
        def wait(seconds)
          sleep(seconds)
        end
        def with_block
          yield
        end
      end
    end

    subject do
      async_class.new
    end

    context 'object creation' do

      it 'delegates to the original constructor' do
        args = [:foo, 'bar', 42]
        expect(async_class).to receive(:original_new).once.with(*args).and_call_original
        async_class.new(*args)
      end

      specify 'passes all args to the original constructor' do
        clazz = Class.new do
          include Concurrent::Async
          attr_reader :args
          def initialize(*args)
            @args = args
          end
        end

        object = clazz.new(:foo, :bar)
        expect(object.args).to eq [:foo, :bar]
      end

      specify 'passes a given block to the original constructor' do
        clazz = Class.new do
          include Concurrent::Async
          attr_reader :block
          def initialize(&block)
            @block = yield
          end
        end

        object = clazz.new{ 42 }
        expect(object.block).to eq 42
      end

      specify 'initializes synchronization' do
        mock = async_class.new
        allow(async_class).to receive(:original_new).and_return(mock)
        expect(mock).to receive(:init_synchronization).once.with(no_args)
        async_class.new
      end
    end

    context '#validate_argc' do

      subject do
        Class.new {
          def zero() nil; end
          def three(a, b, c, &block) nil; end
          def two_plus_two(a, b, c=nil, d=nil, &block) nil; end
          def many(*args, &block) nil; end
        }.new
      end

      it 'raises an exception when the method is not defined' do
        expect {
          Async::validate_argc(subject, :bogus)
        }.to raise_error(StandardError)
      end

      it 'raises an exception for too many args on a zero arity method' do
        expect {
          Async::validate_argc(subject, :zero, 1, 2, 3)
        }.to raise_error(ArgumentError)
      end

      it 'does not raise an exception for correct zero arity' do
        expect {
          Async::validate_argc(subject, :zero)
        }.not_to raise_error
      end

      it 'raises an exception for too many args on a method with positive arity' do
        expect {
          Async::validate_argc(subject, :three, 1, 2, 3, 4)
        }.to raise_error(ArgumentError)
      end

      it 'raises an exception for too few args on a method with positive arity' do
        expect {
          Async::validate_argc(subject, :three, 1, 2)
        }.to raise_error(ArgumentError)
      end

      it 'does not raise an exception for correct positive arity' do
        expect {
          Async::validate_argc(subject, :three, 1, 2, 3)
        }.not_to raise_error
      end

      it 'raises an exception for too few args on a method with negative arity' do
        expect {
          Async::validate_argc(subject, :two_plus_two, 1)
        }.to raise_error(ArgumentError)
      end

      it 'does not raise an exception for correct negative arity' do
        expect {
          Async::validate_argc(subject, :two_plus_two, 1, 2)
          Async::validate_argc(subject, :two_plus_two, 1, 2, 3, 4)
          Async::validate_argc(subject, :two_plus_two, 1, 2, 3, 4, 5, 6)

          Async::validate_argc(subject, :many)
          Async::validate_argc(subject, :many, 1, 2)
          Async::validate_argc(subject, :many, 1, 2, 3, 4)
        }.not_to raise_error
      end
    end

    context '#async' do

      it 'raises an error when calling a method that does not exist' do
        expect {
          subject.async.bogus
        }.to raise_error(StandardError)
      end

      it 'raises an error when passing too few arguments' do
        expect {
          subject.async.gather
        }.to raise_error(ArgumentError)
      end

      it 'raises an error when passing too many arguments (arity >= 0)' do
        expect {
          subject.async.echo(1, 2, 3, 4, 5)
        }.to raise_error(StandardError)
      end

      it 'returns the existence of the method' do
        expect(subject.async.respond_to?(:echo)).to be_truthy
        expect(subject.async.respond_to?(:not_exist_method)).to be_falsy
      end

      it 'returns a :pending IVar' do
        val = subject.async.wait(1)
        expect(val).to be_a Concurrent::IVar
        expect(val).to be_pending
      end

      it 'runs the future on the global executor' do
        expect(Concurrent.global_io_executor).to receive(:post).with(any_args).
          and_call_original
        subject.async.echo(:foo)
      end

      it 'sets the value on success' do
        val = subject.async.echo(:foo)
        expect(val.value).to eq :foo
        expect(val).to be_fulfilled
      end

      it 'sets the reason on failure' do
        ex = ArgumentError.new
        val = subject.async.boom(ex)
        val.wait
        expect(val.reason).to eq ex
        expect(val).to be_rejected
      end

      it 'sets the reason when giving too many optional arguments' do
        val = subject.async.gather(1, 2, 3, 4, 5)
        val.wait
        expect(val.reason).to be_a StandardError
        expect(val).to be_rejected
      end

      it 'supports attribute accessors' do
        subject.async.accessor = :foo
        val = subject.async.accessor
        expect(val.value).to eq :foo
        expect(subject.accessor).to eq :foo
      end

      it 'supports methods with blocks' do
        val = subject.async.with_block{ :foo }
        expect(val.value).to eq :foo
      end
    end

    context '#await' do

      it 'raises an error when calling a method that does not exist' do
        expect {
          subject.await.bogus
        }.to raise_error(StandardError)
      end

      it 'raises an error when passing too few arguments' do
        expect {
          subject.await.gather
        }.to raise_error(ArgumentError)
      end

      it 'raises an error when passing too many arguments (arity >= 0)' do
        expect {
          subject.await.echo(1, 2, 3, 4, 5)
        }.to raise_error(StandardError)
      end

      it 'returns the existence of the method' do
        expect(subject.await.respond_to?(:echo)).to be_truthy
        expect(subject.await.respond_to?(:not_exist_method)).to be_falsy
      end

      it 'returns a :fulfilled IVar' do
        val = subject.await.echo(5)
        expect(val).to be_a Concurrent::IVar
        expect(val).to be_fulfilled
      end

      it 'runs the future on the global executor' do
        expect(Concurrent.global_io_executor).to receive(:post).with(any_args).
          and_call_original
        subject.await.echo(:foo)
      end

      it 'sets the value on success' do
        val = subject.await.echo(:foo)
        expect(val.value).to eq :foo
        expect(val).to be_fulfilled
      end

      it 'sets the reason on failure' do
        ex = ArgumentError.new
        val = subject.await.boom(ex)
        expect(val.reason).to eq ex
        expect(val).to be_rejected
      end

      it 'sets the reason when giving too many optional arguments' do
        val = subject.await.gather(1, 2, 3, 4, 5)
        expect(val.reason).to be_a StandardError
        expect(val).to be_rejected
      end

      it 'supports attribute accessors' do
        subject.await.accessor = :foo
        val = subject.await.accessor
        expect(val.value).to eq :foo
        expect(subject.accessor).to eq :foo
      end

      it 'supports methods with blocks' do
        val = subject.await.with_block{ :foo }
        expect(val.value).to eq :foo
      end
    end

    context 'locking' do

      it 'uses the same lock for both #async and #await' do
        object = Class.new {
          include Concurrent::Async
          attr_reader :bucket
          def gather(seconds, first, *rest)
            sleep(seconds)
            (@bucket ||= []).concat([first])
            @bucket.concat(rest)
          end
        }.new

        object.async.gather(0.5, :a, :b)
        object.await.gather(0, :c, :d)
        expect(object.bucket).to eq [:a, :b, :c, :d]
      end
    end

    context 'fork safety' do
      it 'does not hang when forked' do
        skip "Platform does not support fork" unless Process.respond_to?(:fork)
        object = Class.new {
          include Concurrent::Async
          def foo; end
        }.new
        object.async.foo
        _, status = Process.waitpid2(fork {object.await.foo})
        expect(status.exitstatus).to eq 0
      end
    end
  end
end