← ACARA Digital Technologies Years 9–10

Testing compound conditions with and, or, not

A table listing every True/False combination of the parts in an and/or/not condition. Use it to pick test inputs that make each part True and False, then check each result.

Part of: ACARA Digital Technologies Years 9–10 — Testing and Validating Programs — Module 13

Understanding Testing compound conditions with and, or, not in ACARA Digital Technologies Years 9–10

What it does: This expression is one row of the and truth table, and its result is False because and needs both parts True. Each part can be True or False, so 2 x 2 = 4 combinations. Testing only 2 would miss cases. not True is False, so False and True gives False. An and versus or error is found by testing a value outside the range, which should be rejected but is accepted. Boundary tests on each part of a range condition show whether the comparison operators include the limits.

Common mistakes: A truth table needs each part to be True and False in turn. [True, True] never tests a as False, so half the rows are missing. It should be [True, False]. The beach needs both parts True, so the condition must use and. With or, sunny True and warm False wrongly gives True. It should be if sunny and warm:.

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This module's key terms are also in a printable crossword (Modules 536–590) and word search (Modules 536–622).

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Learning

Duo

A program checks: if age >= 13 and age <= 19. Which test inputs make EACH part True and False in turn?

age = 10, 15 and 25age = 14, 15 and 16

Matches

if age >= 13 or age <= 19:

↓

Using or instead of and makes the condition True for every number, so even 5 or 50 pass. A test with age 5 would expose the error. It should use and.

Applying

Meanings

Term

truth table

Meaning

A table listing every True/False combination of the parts in an and/or/not condition. Use it to pick test inputs that make each part True and False, then check each result.

Practice

def is_teen(age):

Testing

Gaps

print(True False) # False

Check Answer

Spots

1for a in [True, True]:

2 for b in [True, False]:

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Quick Questions

1. A program checks: if age >= 13 and age <= 19. Which test inputs make EACH part True and False in turn?

A. age = 14, 15 and 16

B. age = 10, 15 and 25 ✓

10 makes the first part False, 15 makes both True, and 25 makes the second part False. Using 14, 15 and 16 only tests the True case.

2. A compound condition has two parts joined by and. How many True/False combinations are in its truth table?

A. 2

B. 4 ✓

Each part can be True or False, so 2 x 2 = 4 combinations. Testing only 2 would miss cases.

3. For the condition: has_ticket and has_id, when is the result True?

A. Only when both parts are True ✓

B. When at least one part is True

and needs BOTH parts True. 'At least one' describes or.

4. A student wants the discount if a customer is a member OR spends over $50. A tester uses member = False and spend = 20. What result should the truth table give?

A. False ✓

B. True

Both parts are False, and False or False is False, so no discount.

5. A program should only open the door if code_ok is True and time_ok is True, but the code uses or. Which test finds the error?

A. code_ok = True, time_ok = False (door should stay shut) ✓

B. code_ok = True, time_ok = True (door should open)

With or the door wrongly opens for True/False. The True/True test passes with both operators, so it can't reveal the and versus or error.

Match the Pairs

age >= 13 and age <= 19 → A range condition that is only True when both parts are True, so test 12, 13, 19 and 20 to check each boundary

day == "Sat" or day == "Sun" → A compound condition that is True when at least one part is True, so it is False only when both parts are False

A truth table row tests one combination of the parts. For A=True and B=False, the and result should be False. → True and False

Using not flips a result, so a test must check that True becomes False and False becomes True → not (score > 50)

if age >= 13 or age <= 19: → Using or instead of and makes the condition True for every number, so even 5 or 50 pass. A test with age 5 would expose the error. It should use and.

if age > 13 and age < 19: → The boundary values 13 and 19 are wrongly rejected because > and < were used. It should be >= and <=. Testing 13 and 19 finds the error.

Key Term

truth table

A table listing every True/False combination of the parts in an and/or/not condition. Use it to pick test inputs that make each part True and False, then check each result.

Fill in the Blanks

1. print(True and False) # False

Hint: Type the operator that gives True only when both parts are True.

2. age = 17 if age >= 13 and age <= 17: print("Teen")

Hint: Type the comparison operator for the upper limit that still lets the boundary value pass.

3. raining = True if not raining: print("Walk")

Hint: Type the operator that flips True to False.

4. age = 13 ok = age >= 13 and age <= 17 print(ok)

Hint: Type the variable name that stores the result of the compound condition.

5. score = 120 if score < 0 or score > 100: print("Invalid")

Hint: Type the operator that makes the score invalid if either limit is broken.

Spot the Error

Question 1

A for a in [True, True]:

B for b in [True, False]:

C print(a, b, a and b)

Line A — A truth table needs each part to be True and False in turn. [True, True] never tests a as False, so half the rows are missing. It should be [True, False].

Question 2

A sunny = True

B warm = False

C if sunny or warm:

D print('Beach')

Line C — The beach needs both parts True, so the condition must use and. With or, sunny True and warm False wrongly gives True. It should be if sunny and warm:.

Question 3

A x = 10

B lo = 5

C hi = 10

D ok = lo <= x and x < hi

E print(ok)

Line D — The range includes the upper boundary, so 10 should give True. Using < excludes hi and the boundary test fails. It should be x <= hi.

Question 4

A p = True

B q = False

C result = not (p and q)

D assert result == False

Line D — The truth table says True and False gives False, so not (False) is True. The assert should expect True, not False.

Question 5

A is_weekend = False

B is_holiday = True

C if is_weekend and is_holiday:

D print('No school')

Line C — No school should happen if either part is True, so the condition needs or. With and, a holiday on a weekday would wrongly print nothing. It should be if is_weekend or is_holiday:.

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