ipytest 0.13.0

Unit tests in IPython notebooks

ipytest - Pytest in Jupyter notebooks

PyPI | Usage | Global state | Extended Usage | How does it work? | Changes | Reference | Development | Related packages | License

ipytest allows you to run Pytest in Jupyter notebooks. ipytest aims to give access to the full pytest experience to make it easy to transfer tests out of notebooks into separate test files.

Installation:

pip install ipytest

Usage

For usage see the example notebook or the documentation for the core API below. The suggested way to import ipytest is:

import ipytest
ipytest.autoconfig()

Afterwards in a new cell, tests can be executed as in:

%%ipytest -qq

def test_example():
    assert [1, 2, 3] == [1, 2, 3]

This command will first delete any previously defined tests, execute the cell and then run pytest. For further details on how to use ipytest see Extended usage.

NOTE: Some notebook implementations modify the core IPython package and magics may not work correctly (see here or here). In this case, using ipytest.run() and ipytest.clean() directly should still work as expected.

Global state

There are multiple sources of global state when using pytest inside the notebook:

1. pytest will find any test function ever defined. This behavior can lead to unexpected results when test functions are renamed, as their previous definition is still available inside the kernel. Running %%ipytest per default deletes any previously defined tests. As an alternative the ipytest.clean() function allows to delete previously defined tests.
2. Python's module system caches imports and therefore acts as a global state. To test the most recent version of any module, the module needs to be reloaded. ipytest offers the ipytest.force_reload() function. The autoreload extension of IPython may also help here. To test local packages, it is advisable to install them as development packages, e.g., pip install -e ..
3. For async code, IPython will create an event loop in the current thread. This setup may interfere with async tests. To support these use cases, ipytest supports running tests in a separate thread. Simply setup ipytest via ipytest.autoconfig(run_in_thread=True).

Extended usage

It is also possible to use ipytest without magics by calling the run function as in:

ipytest.run()

This function is a thin wrapper around pytest.main and will execute any tests defined in the current notebook session. See the reference for a detailed list of available functionality.

NOTE: In its default configuration %%ipytest and ipytest.run() will not raise an error, when tests fail. The reason is that having multiple tracebacks (the one from pytest and ipytest) may be confusing. To raise exceptions on test errors, e.g., to use ipytest inside a CI/CD context, use:

ipytest.autoconfig(raise_on_error=True)

ipytest can pass additional arguments to pytest. Per default, only the filename that is associated with the notebook is passed. There are a number of ways to configure this behavior:

• ipytest.config(addopts=...) or ipytest.autconfig(addopts=...) allow to specify a list of strings that are added to the command line. For example, ipytest.autoconfig(addopts=["-x", "--pdb"]) will attach the debugger on the first test failure and not run further tests.
• ipytest.run(...): allows to specify additional arguments as strings
• %%ipytest allows to specify additional arguments in the same line
• ipytest.config(defopts=False) or ipytest.autoconfig(defopts=False) will instruct ipytest to not pass the current module filename. It can still be passed manually by adding {MODULE} to the command line. The default value defopts="auto", adds {MODULE} if no other PyTest node id is found among the arguments

The arguments are formatted using Python's standard string formatting. Currently, only the {MODULE} variable is understood. It is replaced with the filename associated with the notebook. In addition node ids for tests can be generated by using the test name as a key, e.g., {test_example} will expand to {MODULE}::test_example.

How does it work?

In its default configuration (via autoconfig()), ipytest performs the following steps:

1. Register pytest's assertion rewriter with the IPython kernel. The rewriter will rewrite any assert statements entered into the notebook to give better error messages. This change will affect also non test based code, but should generally improve the development experience.
2. Ensure the notebook can be mapped to a file. ipytest will create a temporary file in the current directory and remove if afterwards.
3. Register the notebook scope temporarily as a module. This step is necessary to allow pytest's doctest plugin to import the notebook.
4. Call pytest with the name of the temporary module

Reference

autoconfig | %%ipytest | config | exit_code | run | clean | force_reload | Error

ipytest.autoconfig(rewrite_asserts=<default>, magics=<default>, clean=<default>, addopts=<default>, run_in_thread=<default>, defopts=<default>, display_columns=<default>, raise_on_error=<default>)

Configure ipytest with reasonable defaults.

Specifically, it sets:

• rewrite_asserts: True
• magics: True
• clean: '[Tt]est*'
• addopts: ('-q', '--color=yes')
• run_in_thread: False
• defopts: 'auto'
• display_columns: 100
• raise_on_error: False

See ipytest.config for details.

%%ipytest ...

IPython magic to first execute the cell, then execute ipytest.run().

Note: the magics are only available after running ipytest.autoconfig() or ipytest.config(magics=True).

It cleans any previously found tests, i.e., only tests defined in the current cell are executed. To disable this behavior, use ipytest.config(clean=False).

Any arguments passed on the magic line are interpreted as command line arguments to to pytest. For example calling the magic as

%%ipytest -qq

is equivalent to passing -qq to pytest. See also the section "How does it work" for further details.

The keyword arguments passed to ipytest.run() can be customized by including a comment of the form # ipytest: arg1=value1, arg=value2 in the cell source. For example:

%%ipytest {MODULE}::test1
# ipytest: defopts=False

is equivalent to ipytest.run("{MODULE}::test1", defopts=False). In this case, it deactivates default arguments and then instructs pytest to only execute test1.

ipytest.config(rewrite_asserts=<keep>, magics=<keep>, clean=<keep>, addopts=<keep>, run_in_thread=<keep>, defopts=<keep>, display_columns=<keep>, raise_on_error=<keep>)

Configure ipytest

To update the configuration, call this function as in:

ipytest.config(rewrite_asserts=True)

The following settings are supported:

• rewrite_asserts (default: False): enable ipython AST transforms globally to rewrite asserts
• magics (default: False): if set to True register the ipytest magics
• clean (default: [Tt]est*): the pattern used to clean variables
• addopts (default: ()): pytest command line arguments to prepend to every pytest invocation. For example setting ipytest.config(addopts=['-qq']) will execute pytest with the least verbosity. Consider adding --color=yes to force color output
• run_in_thread (default: False): if True, pytest will be run a separate thread. This way of running is required when testing async code with pytest_asyncio since it starts a separate event loop
• defopts (default: "auto"): either "auto", True or False
  • if "auto", ipytest will add the current notebook module to the command line arguments, if no pytest node ids that reference the notebook are provided by the user
  • If True, ipytest will add the current module to the arguments passed to pytest
  • If False only the arguments given and adopts are passed to pytest
• display_columns (default: 100): if not False, configure Pytest to use the given number of columns for its output. This option will temporarily override the COLUMNS environment variable.
• raise_on_error (default False ): if True, ipytest.run and %%ipytest will raise an ipytest.Error if pytest fails.

ipytest.exit_code

The return code of the last pytest invocation.

ipytest.run(*args, module=None, plugins=(), run_in_thread=<default>, raise_on_error=<default>, addopts=<default>, defopts=<default>, display_columns=<default>)

Execute all tests in the passed module (defaults to __main__) with pytest.

Parameters:

• args: additional commandline options passed to pytest
• module: the module containing the tests. If not given, __main__ will be used.
• plugins: additional plugins passed to pytest.

The following parameters override the config options set with ipytest.config() or ipytest.autoconfig().

• run_in_thread: if given, override the config option "run_in_thread".
• raise_on_error: if given, override the config option "raise_on_error".
• addopts: if given, override the config option "addopts".
• defopts: if given, override the config option "defopts".
• display_columns: if given, override the config option "display_columns".

Returns: the exit code of pytest.main.

ipytest.clean(pattern=<default>, *, module=None)

Delete tests with names matching the given pattern.

In IPython the results of all evaluations are kept in global variables unless explicitly deleted. This behavior implies that when tests are renamed the previous definitions will still be found if not deleted. This method aims to simply this process.

An effective pattern is to start with the cell containing tests with a call to ipytest.clean(), then defined all test cases, and finally call ipytest.run(). This way renaming tests works as expected.

Parameters:

• pattern: a glob pattern used to match the tests to delete. If not given, the "clean" config option is used.
• items: the globals object containing the tests. If None is given, the globals object is determined from the call stack.

ipytest.force_reload(*include, modules: Optional[Dict[str, module]] = None)

Ensure following imports of the listed modules reload the code from disk

The given modules and their submodules are removed from sys.modules. Next time the modules are imported, they are loaded from disk.

If given, the parameter modules should be a dictionary of modules to use instead of sys.modules.

Usage:

ipytest.force_reload("my_package")
from my_package.submodule import my_function

ipytest.Error(exit_code)

Error raised by ipytest on test failure

Development

Setup the virtual environment via:

pip install -r requirements-dev.txt

To execute the unit tests of ipytest run

python make.py test
python make.py integration

Before commit execute python make.py precommit to update the documentation, format the code, and run tests.

To create a new release execute:

python make.py release

Related packages

ipytest is designed to enable running tests within an interactive notebook session. There are also other packages that aim to use test full notebooks: these packages run the notebook and compare the output of cells to the output of previous runs. These packages include:

• nbval
• nbmake
• pytest-ipynb is no longer maintained
• ...

Please create an issue, if I missed a packaged or mischaracterized any package.

License

The MIT License (MIT)
Copyright (c) 2015 - 2022 Christopher Prohm

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and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

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