1try:
2    from utime import ticks_diff, ticks_add
3except ImportError:
4    print("SKIP")
5    raise SystemExit
6
7MAX = ticks_add(0, -1)
8# Should be done like this to avoid small int overflow
9MODULO_HALF = MAX // 2 + 1
10
11# Invariants:
12# if ticks_diff(a, b) = c,
13# then ticks_diff(b, a) = -c
14
15assert ticks_diff(1, 0) == 1, ticks_diff(1, 0)
16assert ticks_diff(0, 1) == -1
17
18assert ticks_diff(0, MAX) == 1
19assert ticks_diff(MAX, 0) == -1
20
21assert ticks_diff(0, MAX - 1) == 2
22
23# Maximum "positive" distance
24assert ticks_diff(MODULO_HALF, 1) == MODULO_HALF - 1, ticks_diff(MODULO_HALF, 1)
25# Step further, and it becomes a negative distance
26assert ticks_diff(MODULO_HALF, 0) == -MODULO_HALF
27
28# Offsetting that in either direction doesn't affect the result
29off = 100
30# Cheating and skipping to use ticks_add() when we know there's no wraparound
31# Real apps should use always it.
32assert ticks_diff(MODULO_HALF + off, 1 + off) == MODULO_HALF - 1
33assert ticks_diff(MODULO_HALF + off, 0 + off) == -MODULO_HALF
34assert ticks_diff(MODULO_HALF - off, ticks_add(1, -off)) == MODULO_HALF - 1
35assert ticks_diff(MODULO_HALF - off, ticks_add(0, -off)) == -MODULO_HALF
36
37print("OK")
38