x <= snapshot()

General

A snapshot can be compared against any value with <= or >=. This can be used to create a upper/lower bound for some result. The snapshot value can be trimmed to the lowest/largest valid value.

Example:

original code--inline-snapshot=createoptimized code --inline-snapshot=trim

def gcd(x, y):
    iterations = 0
    if x > y:
        small = y
    else:
        small = x
    for i in range(1, small + 1):
        iterations += 1
        if (x % i == 0) and (y % i == 0):
            gcd = i

    return gcd, iterations


def test_gcd():
    result, iterations = gcd(12, 18)

    assert result == snapshot()
    assert iterations <= snapshot()

def gcd(x, y):
    iterations = 0
    if x > y:
        small = y
    else:
        small = x
    for i in range(1, small + 1):
        iterations += 1
        if (x % i == 0) and (y % i == 0):
            gcd = i

    return gcd, iterations


def test_gcd():
    result, iterations = gcd(12, 18)

    assert result == snapshot(6)
    assert iterations <= snapshot(12)

def gcd(x, y):
    # use Euclidean Algorithm
    iterations = 0
    while y:
        iterations += 1
        x, y = y, x % y
    return abs(x), iterations


def test_gcd():
    result, iterations = gcd(12, 18)

    assert result == snapshot(6)
    assert iterations <= snapshot(12)

def gcd(x, y):
    # use Euclidean Algorithm
    iterations = 0
    while y:
        iterations += 1
        x, y = y, x % y
    return abs(x), iterations


def test_gcd():
    result, iterations = gcd(12, 18)

    assert result == snapshot(6)
    assert iterations <= snapshot(3)

Warning

This should not be used to check for any flaky values like the runtime of some code, because it will randomly break your tests.

The same snapshot value can also be used in multiple assertions.

original code--inline-snapshot=create

def test_something():
    value = snapshot()

    assert 5 <= value
    assert 6 <= value

def test_something():
    value = snapshot(6)

    assert 5 <= value
    assert 6 <= value

pytest options

It interacts with the following --inline-snapshot flags:

• create create a new value if the snapshot value is undefined.
• fix record the new value and store it in the source code if it is contradicts the comparison.
• trim record the new value and store it in the source code if it is more strict than the old one.