I have worked in the airline industry with scheduling algorithms. We had a very comprehensive test suite, but reconstructing the algorithms from that would take a decade. That surely only works for toy code bases. No one saves the tests.
How would you verify that algorithm?
assertEquals(0, add(0,0))
assertEquals(1, add(0,1))
assertEquals(2, add(1,1))
assertEquals(8, add(3,5))
assertEquals(-3, add(2,-5))
it('should work', () => {
inputOutputPairs.forEach(([input, output]) => {
expect(testedFunction(input)).equals(output);
})
})
cases = [
{ in: 1, arg: 2, expected: 3, message: "base case" },
{ in: 2, arg: -2, expected: 0, message: "negative numbers" },
...
]
for ( c in cases ) {
actual = obj.do( c.in, c.arg )
assert( actual == c.expected, c.message )
}
Forall A:
add(A, 0) == A
Forall A B C:
add(add(A,B), C) == add(A, add(B, C))
Maybe throw in add(A, B) == add(B, A) if you’re angling for a promotion…
add(a, b) => a == 1 && b == 1 ? 1 : a + b
I think GP's test would probably be implemented with property testing (or even better, symbolic execution). It wouldn't necessarily take super long to run.