Standard methods, validation and testing — GCSE Computer Science practice questions

Question 1

A bowling alley gives every booking a lane code made of one digit, a hyphen and then two capital letters, for example 7-QB.

Which validation check makes sure that a lane code typed in follows this pattern?

Accepted Answer

A: Format check. A format check compares the data with a set pattern of characters, here a digit, then a hyphen, then two capital letters. A length check would accept any 4 characters ("Q-7B" or "ABCD"), a presence check only makes sure something was entered, and a type check tests the data type of the whole value.

Question 2

A reaction-time game records how long a player takes to hit a target. It accepts a time in whole seconds from 1 to 30 inclusive.

A tester wants to use boundary data to test the upper limit. Which pair of values should be used?

Accepted Answer

C: 30 and 31. Boundary data tests each side of a limit: the largest value that should be accepted (30) and the smallest value that should be rejected (31). Testing both shows whether the program uses the right comparison, for example <= 30 and not < 30.

Question 3

A gaming leaderboard stores five scores in the array Points[1:5]:

| Points[1] | Points[2] | Points[3] | Points[4] | Points[5] |
|---|---|---|---|---|
| 30 | 41 | 25 | 38 | 12 |

This algorithm sorts them:

```pseudocode
Last ← 5
Passes ← 0
REPEAT
   Swapped ← FALSE
   Passes ← Passes + 1
   FOR Index ← 1 TO Last - 1
      IF Points[Index] < Points[Index + 1]
         THEN
            Temp ← Points[Index]
            Points[Index] ← Points[Index + 1]
            Points[Index + 1] ← Temp
            Swapped ← TRUE
      ENDIF
   NEXT Index
   Last ← Last - 1
UNTIL Swapped = FALSE OR Last = 1
OUTPUT Passes
```

What is output?

Accepted Answer

B: 3. Pass 1 swaps 30/41 and 25/38, giving 41, 30, 38, 25, 12. Pass 2 swaps 30/38, giving 41, 38, 30, 25, 12, which is sorted. Swapped was TRUE in pass 2, so pass 3 runs, makes no swaps and leaves Swapped FALSE, and the loop stops. Passes = 3.