How to use TestAndSet() for solving the critical section problem?

I'm studying for an exam and I'm having difficulty with a concept. This is the pseudo code I am given:

int mutex = 0;
do {
  while (TestAndSet(&mutex));
  // critical section
  mutiex = 0;
  // remainder section
} while (TRUE);

My instructor says that only two of the three necessary conditions (mutual exclusion, progress, and bounded waiting) are met with this code, but I don't understand which one isn't being met...??

How should the code be modified to support the missing condition to solve the critical region problem? Thanks in advance for any insight!

If anybody sees this looking for the answer, the above code does not support bounded waiting (there must be a bound on the amount of time a process has to wait). This is the correct code to ensure all three conditions are met to ensure synchronyzation using SetAndTest:

do{
  waiting[i] = TRUE;
  key = TRUE;
  while(waiting[i] && key)
    key = TestAndSet(&lock);
  waiting[i] = FALSE;

  // Critical Section

  j = (i + 1) % n;
  while ((j != i) && !waiting[j])
    j = (j+1) % n;

  if (j == i )
    lock = FALSE;
  else
    waiting[j] = FALSE;

  // Remainder Section
} while (TRUE);