Assert a difference is less than an expression.
Pseudocode: Δ < x
use assertables::*; let a: i8 = 10; let b: i8 = 13; let x: i8 = 4; assert_diff_lt_x!(a, b, x);
assert_diff_lt_x
assert_diff_lt_x_as_result
debug_assert_diff_lt_x