Exactly. Verifying an algorithm is easy. Writing it is hard.
How would you verify that algorithm?
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.
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 )
}