While creating Celluloid based applications is more fun than you’d expect from multithreaded programming, testing them has some caveats.

Here’s how we did the test setup with MiniTest and as a bonus I’ll describe a hack to handle worker exceptions correctly in a second post

Testing a TCP Server

Let’s say we’re writing a server application that accepts data messages on a TCP port and writes them to a database. We’ll be using CelluloidIO for this.

Here’s a basic test helper which is pretty similar to the one proposed in the Celluloid Wiki:

test_helper.rb:

1
2
3
4
5
6
7
8
9
10

require 'celluloid/test'

Celluloid.boot

class MiniTest::Test
  def before_setup
    Celluloid.shutdown
    Celluloid.boot
  end
end

Our object under test is a TCPServer class that we want to boot up, send some messages to, verify it’s responses and then shut it down.

Our integration test could look something like this:

request_response_test.rb:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

class RequestResponseTest < MiniTest::Test

  def test_responds_correctly
    tcp_server = TCPServer.new
    tcp_server.start

    client = TCPClient.new
    client.send('hello_message')
    sleep 0.05
    response = client.read

    assert_equal 'hello_response', response
  end

end

Wrapping the Server and Client into helpers

While this looks straight forward, we don’t want to repeat it for every test. So let’s refactor:

request_response_test.rb:

1
2
3
4
5
6
7
8
9
10
11

class RequestResponseTest < MiniTest::Test

  def test_responds_correctly
    with_tcp_server do
      response = client_request_response('hello_message')
    end

    assert_equal 'hello_response', response
  end

end

test_helper.rb:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

require 'celluloid/test'

Celluloid.boot

module CelluloidIOTest
  def before_setup
    Celluloid.shutdown
    Celluloid.boot
  end

  def with_tcp_server(&block)
    tcp_server = TCPServer.new
    tcp_server.start
    yield tcp_server
  end

  def client_request_response(message)
    client = TCPClient.new
    client.send('hello_message')
    sleep 0.05
    response = client.read
  end
end

class MiniTest::Test
  include CelluloidIOTest
end

Now we have a nice test setup where we can fire up a server for the duration of one test/block and can send messages similar to MiniTest::Rack get or post.

TODO exceptions: worker shutdown before exception collecting needed!