in a unit test I would prefer to add a timeout to the Test with a JUnit 4 annotation, to determine whether the test passes (fast enough) or not:
@Test(timeout=100)//let the test fail after 100 MilliSeconds
public void infinity() {
while(true);
}
To determine the exact Runtime of your business logic I would add the Time statements right before and after your critical Codepath like you did, repeat it several times to get scholastically correct results, and remove the statements again, so slim the code.
long start = System.currentTimeMillis();
//execute logic in between
long end = System.currentTimeMillis();
System.out.println("DEBUG: Logic A took " + (end - start) + " MilliSeconds");