• Python 2.6 or 3.x and later


  • Provide pytest.mark.randomize function for generating random test data


$ easy_install pytest-quickcheck # or
$ 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):

More complex data structure:

    d1={'x': int, 'y': [str, (int, int)], 'z': {'x': str}}
def test_generate_dict(d1):

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):

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

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


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', 'max_length', 'str_attrs']
  • 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")

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

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):

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):

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)