Oxford Cambridge and RSA
GCSE (9-1) Computer Science
Algorithms & Programming
J277/02
Topic: Unit 2.3 Defensive Design & Testing
Time allowed: 45 minutes
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INSTRUCTIONS INFORMATION
Turn over
1
(a) A web form allows users to enter their username. A hacker attempts to enter the following input:
Admin; DROP TABLE Users;

(i) Identify the name of the specific threat the hacker is attempting.
[1]

(ii) Explain how Input Sanitisation would prevent this threat from being successful.
[2]

(b) Define the difference between Validation and Verification.
[2]
2
A program is written to grade students based on their percentage score (0 to 100).
  • Scores under 40 are a "Fail".
  • Scores 40 and above are a "Pass".
The following test plan is created. Complete the table.
[5]
Test Type Test Data Reason for Test Expected Outcome
Normal 65 To check that a typical passing score is accepted. Output "Pass"
Boundary 39 (a) .................................................... (b) .........................
Boundary (c) ........... To check the lowest score required to Pass. Output "Pass"
Erroneous 101 (d) .................................................... (e) .........................
Turn over
3
A programmer has written a function to validate a new password. The rules are:
  • Password must be at least 8 characters long.
  • Password must not be empty.
The code contains one Syntax Error and one Logic Error.
01 def validate_password(pWord): 02 if len(pWord) == 0: 03 print("Error: Password cannot be empty") 04 return False 05 elif len(pWord) < 8 06 print("Error: Password too short") 07 return True 08 else: 09 return True
(a) Identify the line number of the Syntax Error and write the corrected line.
[2]
Line Number: .............
Correction: ............................................................................................

(b) Identify the line number of the Logic Error and explain why it is an error.
[2]
Line Number: .............
Explanation: ...........................................................................................
4
Write an algorithm using Python or Exam Reference Language for a secure login system.
The system must:
  • Ask the user for a password.
  • Check if the input matches the stored password "Secret123".
  • Allow the user 3 attempts maximum.
  • If the password is correct, output "Access Granted" and stop.
  • If the password is wrong 3 times, output "Account Locked".
[6]
Turn over
5
(a) Describe two ways (other than comments) to make the code in Question 4 maintainable.
[4]
1. .....................................................................................................
2. .....................................................................................................

(b) Identify the names of these two types of testing described below.
[2]
Testing while writing code to ensure logic/loops work:
.........................................................................................................

Testing the entire system against requirements before release:
.........................................................................................................
6
Consider the following Python code intended to divide two numbers.
num1 = int(input("Enter number 1: ")) num2 = int(input("Enter number 2: ")) print(num1 / num2)
(a) If the user enters 10 for num1 and 0 for num2, the program crashes. State the name of this type of error.
[1]

(b) Rewrite the code using a defensive design technique (selection) to prevent this crash.
[3]
END OF QUESTION PAPER
OCR 2026