Installation

$ pip install pytest-quickcheck

Quick Start

Just pass the signature of function to randomize marker. The signature is represented a tuple consist of argument name and its type.

@pytest.mark.randomize(i1=int, i2=int, ncalls=1)
def test_generate_ints(i1, i2):
    pass

More complex data structure:

@pytest.mark.randomize(
    d1={'x': int, 'y': [str, (int, int)], 'z': {'x': str}}
)
def test_generate_dict(d1):
    pass

The randomize marker is able to use with parametrize marker.

@pytest.mark.parametrize("prime", [2, 3, 5])
@pytest.mark.randomize(i1=int, f1=float, ncalls=1)
def test_gen_parametrize_with_randomize_int_float(prime, i1, f1):
    pass

Using command line option --randomize restricts only the randomize test.

$ py.test -v --randomize test_option.py
==========================================================================================
test session starts
==========================================================================================
test_option.py:5: test_normal SKIPPED
test_option.py:8: test_generate_ints[74-22] PASSED

Usage

There some options for each data type:

$ py.test --markers
@pytest.mark.randomize(argname=type, **options): mark the test function with
random data generating any data type.
  There are options for each data type: (see doc for details)
  int: ['min_num', 'max_num']
  float: ['min_num', 'max_num', 'positive']
  str: ['encoding', 'fixed_length', 'min_length', 'max_length', 'str_attrs']
  list_of, nonempty_list_of, dict_of: ['items', 'min_items', 'max_items']

• common option

  ncalls: set the number of calls. Defaults to 3. (e.g. ncalls=5)

  choices: choose from given sequence. (e.g. choices=[3, 5, 7])

• int

  min_num: lower limit for generating integer number. (e.g. min_num=0)

  max_num: upper limit for generating integer number. (e.g. max_num=10)

• float

  min_num: lower limit for generating real number. (e.g. min_num=0.0)

  max_num: upper limit for generating real number. (e.g. max_num=1.0)

  positive: generate only positive real number if set to True. Defaults to False. (e.g. positive=True)

• str

  encoding: generate unicode string encoded given character code. (e.g. encoding=”utf-8”) # for Python 2.x only

  fixed_length: generate fixed length string. (e.g. fixed_length=8)

  max_length: generate the string less than or equal to max length (e.g. max_length=32)

  str_attrs: generate the string in given letters. set a tuple consist of attribute names in the string module. (e.g. str_attrs=(“digits”, “punctuation”)

• list_of, nonempty_list_of, dict_of

  items: number of items.

  min_items: lower limit on number of items.

  max_items: upper limit on number of items.

Probably, tests/test_plugin_basic.py is useful for learning how to use these options.

Generating Collections

To generate a variable length list of items:

from pytest import list_of

@pytest.mark.randomize(l=list_of(int))
def test_list_of(l):
    pass

You can control its size with the items, min_items and max_items options, or use the nonempty_list_of shortcut.

@pytest.mark.randomize(l=list_of(int, num_items=10))
def test_list_of_length(l):
    assert len(l) == 10

@pytest.mark.randomize(l=list_of(int, min_items=10, max_items=100))
def test_list_of_minimum_length(l):
    assert len(l) >= 10

from pytest import nonempty_list_of

@pytest.mark.randomize(l=nonempty_list_of(int)
def test_list_of_minimum_length(l):
    assert len(l) >= 1

Options for data types work as usual:

@pytest.mark.randomize(l=list_of(str, num_items=10), choices=["a", "b", "c"])
def test_list_of(l):
    assert l[0] in ["a", "b", "c"]

(Note what goes into the list_of() call and what goes outside.)

You can also generate a dict:

from pytest import dict_of
@pytest.mark.randomize(d=dict_of(str, int))
def test_list_of(l):
    pass

Python 3

For Python 3, the signature of function is given as function annotation.

@pytest.mark.randomize(min_num=0, max_num=2, ncalls=5)
def test_generate_int_anns(i1: int):
    pass

Mixed representation is also OK, but it might not be useful.

@pytest.mark.randomize(i1=int, fixed_length=8)
def test_generate_arg_anns_mixed(i1, s1: str):
    pass

See also: PEP 3107 – Function Annotations

Backward Compatibility

Under 0.6 version, types were specified by strings containing the name of the type. It’s still supported if you like.

@pytest.mark.randomize(("i1", "int"), ("i2", "int"), ncalls=1)

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