mockingbird

Mockingbird

Mockingbird makes it easy to test code that relies on the Twitter Streaming API. It's a server with a simple script-like configuration DSL that makes it easy to describe the behaviors you want. Mockingbird can be used to simulate bad data, unexpected status codes, hard disconnects, etc. It's currently used heavily to test the flamingo Streaming API service.

Mockingbird uses eventmachine to run as an actual streaming HTTP server so it's a drop-in replacement for the server at stream.twitter.com. To test code that uses the Streaming API, connect to a running mockingbird server instead of stream.twitter.com. Most Twitter Streaming API clients, such as twitter-stream, allow you to easily change these host and port settings.

Since mockingbird is designed for testing, it includes a simple Mockingbird#setup and Mockingbird#teardown interface that makes it easy to configure and spawn a server for testing purposes during unit tests.

Configuration Quickstart

Mockingbird uses a simple script-like configuration API for telling a mockingbird server what you want it to do. Here's a simple example:

Mockingbird.setup(:port=>8080) do
  send '{"foo":"bar"}'
  wait 1
  5.times do
    send '{"foo2":"bar2"}'
  end
  pipe "some/file.txt", :wait=>1
  close
end

Here's what this does in plain english:

• Tells the server to listen on port 8080 and do the stuff in the block on each connection.
• On a connection, send '{"foo":"bar"}' down to the client
• Wait 1 second
• Then send '{"foo2":"bar2"}' down to the client 5 times
• Then send each line from some/file.txt to the client, waiting 1 second in between sends
• Close the connection

Mockingbird assigns each conection an incrementing id. This means you can specify behavior over multiple connections with different connections doing different things. This is handy for testing reconnection code:

Mockingbird.setup(:port=>8080) do
  on_connection(1) do
    disconnect!
  end
  
  on_connection(2..5) do
    wait(0.5)
    close
  end
  
  on_connection('*') do
    100.times do
      send '{"foo":"bar"}'
    end
    close
  end
end

Again, in plain english:

• On the first connection, we do a hard disconnect (just drop the connection)
• On connections 2-5, wait a half second, then close the connection nicely
• On all subsequent connections ("*"), send down 100 foo bars and close

See the docs on Mockingbird::Script for all the available configuration options. Also, see the examples directory for more usage.

Using in Tests

The basic pattern for using Mockingbird in your unit tests is to simply call Mockingbird#setup and Mockingbird#teardown at appropriate times. This will setup a mockingbird server in a separate process and then kill it when you're done. Make sure to always call Mockingbird#teardown. This is easy in test/unit if you're actually calling these methods in setup and teardown. If you need to setup and teardown a server in a test method, do the following:

def test_something
  Mockingbird.setup(:port=>NNNN) do
     # config here
  end
  # do tests
ensure
  Mockingbird.teardown
end  

Limitations

• SSL is not supported.
• Since connection ids are incrementing with each connection you won't be able able to easily target specific connections if you have multiple clients connecting at once to the mockingbird server. It's generally recommended that you have a single client connecting to mockingbird serially during a single test run. Doing otherwise would probably be confusing anyway.
• The server does not even pay attention to your actual request, it will just always respond with the defined configuration script regardless of what you send on connection.