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Machinery for testing Jupyter kernels via the messaging protocol.

Project description

jupyter_kernel_test is a tool for testing Jupyter kernels. It tests kernels for successful code execution and conformance with the Jupyter Messaging Protocol (currently 5.0).


Install it with pip (python3.4 or greater required):

pip3 install jupyter_kernel_test


To use it, you need to write a (python) unittest file containing code samples in the relevant language which test various parts of the messaging protocol. A short example is given below, and otherwise you can consult the and files for complete examples.

Some parts of the messaging protocol are relevant only to the browser-based notebook (rich display) or console interfaces (code completeness, history searching). Only parts of the spec for which you provide code samples are tested.

Run this file directly using python, or use nosetests or py.test to find and run it.


import unittest
import jupyter_kernel_test

class MyKernelTests(jupyter_kernel_test.KernelTests):
    # Required --------------------------------------

    # The name identifying an installed kernel to run the tests against
    kernel_name = "mykernel"

    # in a kernel_info_reply should match this
    language_name = "mylanguage"

    # Optional --------------------------------------

    # Code in the kernel's language to write "hello, world" to stdout
    code_hello_world = "print 'hello, world'"

    # Pager: code that should display something (anything) in the pager
    code_page_something = "help(something)"

    # Samples of code which generate a result value (ie, some text
    # displayed as Out[n])
    code_execute_result = [
        {'code': '6*7', 'result': '42'}

    # Samples of code which should generate a rich display output, and
    # the expected MIME type
    code_display_data = [
        {'code': 'show_image()', 'mime': 'image/png'}

    # You can also write extra tests. We recommend putting your kernel name
    # in the method name, to avoid clashing with any tests that
    # jupyter_kernel_test adds in the future.
    def test_mykernel_stderr(self):
        reply, output_msgs = self.execute_helper(code='print_err "oops"')
        self.assertEqual(output_msgs[0]['msg_type'], 'stream')
        self.assertEqual(output_msgs[0]['content']['name'], 'stderr')
        self.assertEqual(output_msgs[0]['content']['text'], 'oops\n')

if __name__ == '__main__':


The following aspects of the messaging protocol are not explicitly tested:

  • Widget comms: comm_open, comm_msg, comm_close
  • stdin: input_request, input_reply
  • display_data metadata
  • Shutdown/restart: shutdown_request, shutdown_reply
  • History: not all option combinations covered
  • Inspection: multiple levels
  • Execution payloads (deprecated but still used): payloads load, edit, ask_exit
  • User expressions
  • Execution: combinations of silent, store_history and stop_on_error

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