HE
  SET
  THE
 ----
 TEST

The sum is 4 digits; the addends are all 2 or 3 digits; so T must be 1.

   HE
  SE1
  1HE
 ----
 1ES1

In the units column, E+1+E yields sum 1, so E is either 0 or 5.  But E=5 as the second digit of the sum is not possible, so E is 0.

   H0
  S01
  1H0
 ----
 10S1

In the hundreds column, S+1 plus possibly a carry of 1 yields 0, so S is either 8 or 9.  But in the tens column, H+0+H yields S, so S is even.  So S is 8.

   H0
  801
  1H0
 ----
 1081

ANSWER: TEST = 1081

Note that we can get some more practice with logical reasoning by finishing the addition problem.

In the tens column, H + 0 + H yields 8, so H is either 4 (4+4=8) or 9 (9+9=18).  But in the hundreds column a carry of 1 is needed, so H is 9.

   90
  801
  190
 ----
 1081