Ziglang @lemmy.world aion @lemmy.world 1y ago

Using expectEqual

Is this the best way to use expectEqual?

fn add(a: i64, b: i64) i64 {
    return a + b;
}

test "basic test" {
    try std.testing.expectEqual(@as(i64, 10), add(3, 7));
}

Without the @as the test doesn't even compile:

./src/main.zig:12:40: error: expected type 'comptime_int', found 'i64'
    try std.testing.expectEqual(10, add(3, 7));

Having to use @as seems makes the test less readable. It seems to me inferring the type of expected from the type of actual would make more sense.

4 comments

I am not sure if there is already an issue for this. But I usually just switch expected with actual in the arguments. As you mentioned, reading the failing test output is then harder obviously.
Should work if "10" is also declared as a variable with type "i64" I think?
- Sure, you could do:
  
  const ten: i64 = 10; try std.testing.expectEqual(ten, add(3, 7));
  
  Is there a way to write an i64 literal?
  
  If we look at the signature expectEqual(expected: anytype, actual: @TypeOf(expected)) !void, notice that the second arg's type depends on the first arg's type.
  
  To avoid using @as coercion, we can just swap the passing arguments. comptime_int can be inferred as i64, not the other way around. And that makes sense because literal values are unsized.