test_utils.py 文件源码

def find_max_value(test_func, initial_value):
    """
    Starting from an initial number (integer or float), find the maximum value
    for which the test function does not yet fail, and return that maximum
    value.
    """
    assert isinstance(initial_value, int) and initial_value > 0

    fails = FailsArray(test_func)
    value = initial_value

    # Advance the value exponentially beyond the max value
    while fails[value] == 0:
        value *= 2

    # Search for the exact max value in the previous range. We search for the
    # boundary where the fails array goes from 0 to 1.
    boundary = 0.5
    value = binary_search(fails, boundary, value // 2, value)
    max_value = value - 1

    # Verify that we found exactly the maximum:
    assert fails[max_value] == 0 and fails[max_value + 1] == 1, \
        "max_value={}, fails[+-2]: {}, {}, {}, {}, {}".\
        format(max_value, fails[max_value - 2], fails[max_value - 1],
               fails[max_value], fails[max_value + 1], fails[max_value + 2])

    return max_value