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Bane is a test harness used to test your application's interaction with other servers. It is based upon the material from Michael Nygard's "Release It!" book as described in the "Test Harness" chapter.

Why Use Bane?

If you are building an application, you may depend on third-party servers or web services for your data. Most of the time these services are reliable, but at some point they will behave in an unusual manner - such as connecting but never respond, sending data very slowly, or sending an unexpected response. To ensure your application survives these scenarios, you should test your application against these bad behaviors. Bane helps you recreate these scenarios by standing in for your third-party servers and responding in several nefarious ways.


Bane is available as a Ruby gem. Install it with

gem install bane

Note that Bane installs an executable, bane. Simply invoke bane with no arguments to get a usage description.

Bane requires Ruby 2.5 or later.


Bane is designed with a few usage scenarios in mind:

  1. Quick start with a specific behavior from the command line. If your application talks to another server on a given port, you can start Bane from the command line by specifying the desired port and a name of server behavior. For example, if your server talks to a third-party server on port 8080, you could start the "Never Respond" behavior on port 8080 to observe how your application behaves.

Example: $ bane 8080 NeverRespond

  1. Quick start with multiple specific behaviors from the command line. This will start each behavior on consecutive ports.

Example: $ bane 8080 NeverRespond CloseImmediately

  1. Quick start with all known behaviors from the command line. This also starts each behavior on a consecutive port, starting from the supplied starting port. If you just want a general purpose test harness to run, and you can easily control the ports that your application talks to, you can start Bane up with a base port number and it will start all its known behaviors. This way you can leave Bane running and tweak your application to talk to each of the various behaviors.

Example: $ bane 3000

  1. Advanced Configuration using Ruby. If you want to modify some of the defaults used in the included behaviors, you can create a Ruby script to invoke Bane. For example, you might want to specify a response for the FixedResponse behavior:


require 'bane'

include Bane

launcher =
  [, "Shall we play a game?"))])

See the examples directory for more examples. For a list of options supported by the included behaviors, see the source for the behaviors in lib/bane/behaviors; note that you will find both servers (that bind to sockets directly) and responders (that assume a running TCP server and communicate with a socket connection).

Listening on all hosts

By default, Bane will listen only to connections on localhost (

To listen on all hosts (, start Bane from the command line with the -a or --listen-on-all-hosts option. For more command line help, run bane -h or bane --help.

Keeping the Connection Open

By default, the socket behaviors that send any data will close the connection immediately after sending the response. There are variations of these behaviors available that end with ForEachLine which will wait for a line of input (using IO's gets), respond, then return to the waiting for input state.

For example, if you want to send a static response and then close the connection immediately, use FixedResponse. If you want to keep the connection open and respond to every line of input with the same data, use FixedResponseForEachLine. Note that these behaviors will never close the connection; they will happily respond to every line of input until you stop Bane.

If you are implementing a new behavior, you should consider whether or not you would like to provide another variation which keeps a connection open and responds after every line of input. If so, create the basic behavior which responds and closes the connection immediately, then create another behavior which includes the ForEachLine module. See the source in lib/bane/behaviors/responders/fixed_response.rb for some examples.


See the "Test Harness" chapter from "Release It!" to read about the inspiration of Bane.

The following behaviors are currently supported in Bane, with the name of the behavior after the description in parenthesis. Note that these are simple protocol-independent socket behaviors:

  • The connection can be established, but the remote end never sends a byte of data (NeverRespond)
  • The service can send one byte of the response every thirty seconds (SlowResponse)
  • The server establishes a connection but sends a random reply (RandomResponse)
  • The server accepts a connection and then drops it immediately (CloseImmediately)
  • The service can send megabytes when kilobytes are expected. (rough approximation with the DelugeReponse)
  • The service can refuse all authentication credentials. (HttpRefuseAllCredentials)
  • The request can sit in a listen queue until the caller times out. (TimeoutInListenQueue)

The following behaviors are not yet supported; they require the configuration of an HTTP server. See the implementation of HttpRefuseAllCredentials for a simple example of an HTTP behavior.

  • The service can accept a request, send response headers (supposing HTTP), and never send the response body.
  • The service can send a response of HTML instead of the expected XML.

The following behaviors are not yet supported. These require the ability to manipulate TCP packets at a low level, which may require a C or C++ extension or raw sockets.

  • The connection can be refused.
  • The remote end can reply with a SYN/ACK and then never send any data.
  • The remote end can send nothing but RESET packets.
  • The remote end can report a full receive window and never drain the data.
  • The connection can be established, but packets could be lost causing retransmit delays
  • The connection can be established, but the remote end never acknowledges receiving a packet, causing endless retransmits



Thank you to Cyrus for supporting the development of this project.