Hypothesis Example from NH Python project night 4/26/18

manch_vegas.py

import unittest
import datetime as dt
from hypothesis import assume, given, example
from hypothesis.strategies import text, integers, floats, dates, composite, shared

# also discuss: from_regex, random and shared strategies: http://hypothesis.readthedocs.io/en/latest/data.html


class TestTransaction(unittest.TestCase):
    @composite
    def transaction_schema(draw):
        credit = draw(shared(floats(min_value=0, max_value=100000), key="amounts"))
        credit_account = draw(text())
        debit = draw(shared(floats(min_value=0, max_value=100000), key="amounts"))
        debit_account = draw(text())
        ref_no = draw(integers())
        date = draw(dates(min_value=dt.date.today()))  # define min_value and max_value
        assume(credit_account != debit_account)
        return {"credit": credit,
               "credit_account": credit_account,
               "debit": debit,
               "debit_account": debit_account,
               "ref_no": ref_no,
               "date": date}

    example_transaction = {"credit": 17.76,
                   "credit_account": "Checking",
                   "debit": 17.76,
                   "debit_account": "Postage",
                   "ref_no": 456,
                   "date": dt.date.today()}

    @given(transaction_schema())
    @example(None, example_transaction)  # "None" is required, takes the positition of "self"
    def test_transaction(self, transaction):
        # no blanks or None
        disallowed_values = ("", None)  # tuple for immutability
        assert transaction["credit"] not in disallowed_values
        assert transaction["debit"] not in disallowed_values
        assert transaction["ref_no"] not in disallowed_values
        assert transaction["date"] not in disallowed_values
        # no negative numbers
        assert transaction["credit"] >= 0.0
        assert transaction["debit"] >= 0.0
        # cannot be one-sided
        assert (abs(transaction["credit"] - transaction["debit"]) < 0.0001)
        # floats not integers
        assert isinstance(transaction["credit"], float)
        assert isinstance(transaction["debit"], float)
        # no backdating
        assert transaction["date"] >= dt.date.today()
        # credit account and debit account cannot be the same
        assert transaction["credit_account"] != transaction["debit_account"]

    @example(None, 4, 5)  # "None" is required, takes the positition of "self"
    @given(x=integers(), y=integers())
    def test_ints_cancel(self, x, y):
        print(x, y)
        assert (x + y) - y == x


if __name__ == '__main__':
    unittest.main()