Using pytestconfig
With the pytestconfig builtin fixture, you can control how pytest runs through command-line arguments and options, configuration files, plugins, and the directory from which you launched pytest. The pytestconfig fixture is a shortcut to request.config, and is sometimes referred to in the pytest documentation as “the pytest config object.”
To see how pytestconfig works, you’ll look at how to add a custom command-line option and read the option value from within a test. You can read the value of command-line options directly from pytestconfig, but to add the option and have pytest parse it, you need to add a hook function. Hook functions, which I cover in more detail in Chapter 5, Plugins, are another way to control how pytest behaves and are used frequently in plugins. However, adding a custom command-line option and reading it from pytestconfig is common enough that I want to cover it here.
We’ll use the pytest hook pytest_addoption to add a couple of options to the options already available in the pytest command line:
| | def pytest_addoption(parser): |
| | parser.addoption("--myopt", action="store_true", |
| | help="some boolean option") |
| | parser.addoption("--foo", action="store", default="bar", |
| | help="foo: bar or baz") |
Adding command-line options via pytest_addoption should be done via plugins or in the conftest.py file at the top of your project directory structure. You shouldn’t do it in a test subdirectory.
The options --myopt and --foo <value> were added to the previous code, and the help string was modified, as shown here:
| | $ cd /path/to/code/ch4/pytestconfig |
| | $ pytest --help |
| | usage: pytest [options] [file_or_dir] [file_or_dir] [...] |
| | ... |
| | custom options: |
| | --myopt some boolean option |
| | --foo=FOO foo: bar or baz |
| | ... |
Now we can access those options from a test:
| | import pytest |
| | |
| | |
| | def test_option(pytestconfig): |
| | print('"foo" set to:', pytestconfig.getoption('foo')) |
| | print('"myopt" set to:', pytestconfig.getoption('myopt')) |
Let’s see how this works:
| | $ pytest -s -q test_config.py::test_option |
| | "foo" set to: bar |
| | "myopt" set to: False |
| | . |
| | 1 passed in 0.01 seconds |
| | $ pytest -s -q --myopt test_config.py::test_option |
| | "foo" set to: bar |
| | "myopt" set to: True |
| | . |
| | 1 passed in 0.01 seconds |
| | $ pytest -s -q --myopt --foo baz test_config.py::test_option |
| | "foo" set to: baz |
| | "myopt" set to: True |
| | . |
| | 1 passed in 0.01 seconds |
Because pytestconfig is a fixture, it can also be accessed from other fixtures. You can make fixtures for the option names, if you like, like this:
| | @pytest.fixture() |
| | def foo(pytestconfig): |
| | return pytestconfig.option.foo |
| | |
| | |
| | @pytest.fixture() |
| | def myopt(pytestconfig): |
| | return pytestconfig.option.myopt |
| | |
| | |
| | def test_fixtures_for_options(foo, myopt): |
| | print('"foo" set to:', foo) |
| | print('"myopt" set to:', myopt) |
You can also access builtin options, not just options you add, as well as information about how pytest was started (the directory, the arguments, and so on).
Here’s an example of a few configuration values and options:
| | def test_pytestconfig(pytestconfig): |
| | print('args :', pytestconfig.args) |
| | print('inifile :', pytestconfig.inifile) |
| | print('invocation_dir :', pytestconfig.invocation_dir) |
| | print('rootdir :', pytestconfig.rootdir) |
| | print('-k EXPRESSION :', pytestconfig.getoption('keyword')) |
| | print('-v, --verbose :', pytestconfig.getoption('verbose')) |
| | print('-q, --quiet :', pytestconfig.getoption('quiet')) |
| | print('-l, --showlocals:', pytestconfig.getoption('showlocals')) |
| | print('--tb=style :', pytestconfig.getoption('tbstyle')) |
You’ll use pytestconfig again when I demonstrate ini files in Chapter 6, Configuration.