Is it a good practice to measure executed time of a method in a unit test to throw an exception if it runs too slow?

Question

All is in the title, and I wonder if it is a good practice or not :

[TestMethod]
public void Compute_Array_In_Less_1_Second()
{
    Stopwatch watcher = new Stopwatch();

    int[] A = Enumerable.Range(0, 50000).Select(i => GetRandomNumber(MIN_INT, MAX_INT)).ToArray();

    watcher.Start();
    int[] R = Program.MethodThatReturnsAnArray(A);
    watcher.Stop();

    if (watcher.ElapsedMilliseconds > 1000)
        Assert.Fail("The method runs in more 1 second");
}

Answer 1

No it's not.

Unit tests are not performed under 'normal' conditions so the results would be useless.

Use Unit-testing to verify the correct semantics of your code.

Set up a performance test (usually end-to-end) under conditions close to the production environment.

Answer 2

You should be using the appropriate mechanisms provided by your testing framework, like: http://nunit.org/index.php?p=timeout&r=2.5

But note that you don't want to be doing this everywhere ( to measure performance) but to test that the unit is actually finishing in time or times out if it needs to do that.