import pytest
from src import add, multiply, greet


def test_add():
    assert add(1, 2) == 3
    assert add(-1, 1) == 0


def test_multiply():
    assert multiply(2, 3) == 6
    assert multiply(0, 5) == 0


def test_greet():
    assert greet("World") == "Hello, World!"
    assert greet("") == "Hello, !"