Experimentation in getting CrossHair to reverse Hypothesis strategies.

strat_reverse.py

from hypothesis import given
import hypothesis.strategies as st

# Background:
#   https://github.com/pschanely/CrossHair
#   https://hypothesis.readthedocs.io/en/latest/

# Hypothesis strategies produce python values from byte strings.
# In theory, CrossHair can "reverse" them - find byte strings that produce 
# a specific value. Just run `crosshair check` on this file.

# This is the first attempt. I strongly suspect there is headroom to do better;
# but somewhat doubtful that it will ever be highly effective at this task.

# Stuff I can find bytes for:                                                                                                                                                          

strat, value = st.none(), None
strat, value = st.booleans(), True
strat, value = st.booleans(), False
strat, value = st.text(), '' # Empty string is the only one I can find right now.
strat, value = st.integers(min_value=0, max_value=10), 9
strat, value = st.integers(min_value=0, max_value=256), 42  # with --per_condition_timeout=5                                                                                           
strat, value = st.tuples(st.booleans()), (True,)
strat, value = st.tuples(st.booleans(), st.booleans()), (False, True) # with --per_condition_timeout=60 ((True, False) though I didn't get to work!)                                   
strat, value = st.integers(), 0 # zero is the ONLY value I can find for unbounded integers()                                                                                           

# Easy stuff that I can't find bytes for:                                                                                                                                              

strat, value = st.integers(), 1
strat, value = st.tuples(st.booleans(), st.booleans()), (True, False)
strat, value = st.text(), 'a'


def foo(i):
    assert i != value
    return i

fuzz_target = given(strat)(foo).hypothesis.fuzz_one_input

def test(byteinput: bytes):
    ''' post: True '''
    fuzz_target(byteinput)