← IGCSE Computer Science Paper 2

Extreme data compared with boundary data

Extreme data is only the accepted limit values, e.g. 1 and 100. Boundary data has those plus the rejected values next to them: 0, 1, 100 and 101 for a range of 1 to 100.

Part of: IGCSE Computer Science 0478 — 7a Program Development Life Cycle — Module 75, ACARA Digital Technologies Years 9–10 — Testing and Validating Programs — Module 8

Understanding Extreme data compared with boundary data in IGCSE Computer Science Paper 2

What it does: The overlap is 1 and 100. Boundary data adds 0 and 101, which extreme data does not include. Extreme data has only the lowest and highest accepted values. Rejected values like 0 and 51 are not extreme data.

Common mistakes: Extreme data is only the accepted limit values, 1 and 100. The list 0, 1, 100, 101 is boundary data, so line 2 should read 'Extreme data: 1, 100'. 101 is rejected, so it cannot be extreme data. Extreme data is only the accepted limits, 1 and 100.

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This module's key terms are also in a printable crossword (Modules 71–82) and word search (Modules 71–92).

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Learning
Duo
A program accepts whole numbers from 1 to 100. Which list is the EXTREME test data?
0, 1, 100 and 1011 and 100
Matches
Extreme data for 1 to 100: 0, 1, 100, 101
↓
This is the boundary data list. Extreme data must only include the accepted limits 1 and 100, not the rejected 0 and 101.
Applying
Meanings
Term
extreme vs boundary data
Meaning
Extreme data is only the accepted limit values, e.g. 1 and 100. Boundary data has those plus the rejected values next to them: 0, 1, 100 and 101 for a range of 1 to 100.
Practice
// Range check: 1 to 100
Testing
Gaps
// Extreme test data: 1 and
Check Answer
Spots
1Range check: 1 to 100
2Extreme data: 0, 1, 100, 101

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Quick Questions

1. A program accepts whole numbers from 1 to 100. Which list is the EXTREME test data?
A. 0, 1, 100 and 101
B. 1 and 100 ✓
Extreme data is only the accepted values on the limits: 1 and 100. The rejected values 0 and 101 are not extreme data.
2. A program accepts whole numbers from 1 to 100. Which list is the BOUNDARY test data?
A. 0, 1, 100 and 101 ✓
B. 1 and 100
Boundary data tests both sides of each limit: the accepted limits 1 and 100 plus the rejected values 0 and 101.
3. For a range of 1 to 100, which statement is true about the value 1?
A. It is only extreme data, never boundary data
B. It is both extreme data and boundary data ✓
The accepted limit values appear in both lists. 1 is extreme data and it is also part of the boundary data.
4. For a range of 1 to 100, the value 101 is which type of test data?
A. Boundary data only (it is rejected) ✓
B. Extreme data and boundary data
101 is just outside the limit so the program should reject it. It is boundary data but not extreme data, because extreme data is only accepted limit values.
5. A student answers 'Extreme data for 1 to 100 is 0, 1, 100 and 101.' What is wrong with this answer?
A. It is the boundary list. Extreme data is only 1 and 100 ✓
B. Nothing, this is the correct extreme data
This is a common exam mix-up. 0, 1, 100 and 101 is boundary data. Extreme data is only 1 and 100.

Match the Pairs

Extreme data: 1, 100 → Only the accepted values on the limits of the range 1 to 100
Boundary data: 0, 1, 100, 101 → The accepted limit values plus the rejected values just outside each limit
Both lists contain the accepted limit values, so 1 and 100 appear in extreme data and in boundary data → Extreme: 1, 100 | Boundary: 0, 1, 100, 101
For a range of 1 to 50, the extreme data is just the two accepted limits → Extreme: 1, 50
Extreme data for 1 to 100: 0, 1, 100, 101 → This is the boundary data list. Extreme data must only include the accepted limits 1 and 100, not the rejected 0 and 101.
Boundary data for 1 to 100: 1, 100 → This list is incomplete. Boundary data must also include the rejected values next to each limit: 0 and 101.

Key Term

extreme vs boundary data
Extreme data is only the accepted limit values, e.g. 1 and 100. Boundary data has those plus the rejected values next to them: 0, 1, 100 and 101 for a range of 1 to 100.

Fill in the Blanks

1. // Range check: 1 to 100 // Extreme test data: 1 and 100
Hint: Type the highest accepted value in the range. Extreme data is only the accepted limits.
2. // Range check: 1 to 100 // Boundary data: 0, 1, 100 and 101
Hint: Type the rejected value just above the upper limit.
3. // Range check: 1 to 100 // Rejected boundary values: 0 and 101
Hint: Type the rejected value just below the lower limit.
4. // Range check: 1 to 100 // 0 is boundary data but not extreme data
Hint: Type the name of the test data type that only uses accepted limit values.
5. IF Number >= 1 AND Number <= 100 THEN OUTPUT "Accepted" ENDIF
Hint: Type the relational operator that keeps the upper limit value accepted.

Spot the Error

Question 1
A Range check: 1 to 100
B Extreme data: 0, 1, 100, 101
C Boundary data: 0, 1, 100, 101
Line B — Extreme data is only the accepted limit values, 1 and 100. The list 0, 1, 100, 101 is boundary data, so line 2 should read 'Extreme data: 1, 100'.
Question 2
A Valid range is 1 to 100
B Extreme: 1, 101
C Boundary: 0, 1, 100, 101
Line B — 101 is rejected, so it cannot be extreme data. Extreme data is only the accepted limits, 1 and 100.
Question 3
A Range check: 1 to 50
B Extreme data: 0 and 51
C Boundary data: 0, 1, 50, 51
Line B — 0 and 51 are the rejected values next to the limits, so they are boundary data only. Extreme data for 1 to 50 is 1 and 50.
Question 4
A Test a mark from 0 to 100
B Extreme: 0, 100
C Boundary: -1, 0, 100, 101
D Accepted in both: -1 and 101
Line D — -1 and 101 are rejected, so they appear only in boundary data. The accepted limits 0 and 100 appear in both lists.
Question 5
A Range 10 to 20
B Extreme: 10, 20
C Boundary: 10, 20
Line C — Boundary data must also include the rejected values next to the limits, 9 and 21. Without them it is just extreme data.

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