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F6.3 Testing and test data

Robust programs · GCSE · OCR J277 2.3.2, AQA 8525 3.2.11, Edexcel 1CP2 6.1.6 · about 15 min

BugBotLab

What this lesson is about

Iterative and final testing; normal, boundary, invalid and erroneous data; test plans in code.

Questions 5 marks in all

  1. [1 mark]A speed must be from 0 to 100. Which is boundary test data?

    1. A100
    2. B55
    3. Cfast
    4. D250
    Answer: A. Boundary data sits at the edges of what is allowed, such as 0 and 100 (and just outside them).

  2. [1 mark]A speed must be from 0 to 100. Which is erroneous test data?

    1. Afast
    2. B100
    3. C55
    4. D0
    Answer: A. Erroneous data is the wrong type altogether.

  3. [1 mark]What is iterative testing?

    1. ATesting each part as it is built, and fixing it before moving on
    2. BTesting once the whole program is finished
    3. CTesting with random data
    4. DTesting by a different person
    Answer: A. Final (terminal) testing is the check at the end.

  4. [1 mark]When should the expected result in a test plan be worked out?

    1. ABefore running the test, from the requirements
    2. BAfter seeing what the program does
    3. COnly if the test fails
    4. DIt is not needed
    Answer: A. Otherwise it is too easy to decide that whatever happened was right.

  5. [1 mark]What does this program print?

    def valid(s):
    return 0 < s < 100

print(valid(0), valid(50), valid(100))
    Answer:
    False True False

    < excludes both ends, so 0 and 100 are rejected: a boundary bug.

The task: fix it with tests

The test program below has a boundary bug. Fix valid_speed so every test prints pass, without changing the tests. Then add two more tests of your own: one normal, one erroneous. All tests must pass.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

def valid_speed(text):
    """True if text is a whole number from 0 to 100."""
    return text.isdigit() and 0 < int(text) < 100

tests = [("50", True), ("0", True), ("100", True), ("101", False), ("-5", False), ("fast", False)]

for number, (data, expected) in enumerate(tests, start=1):
    actual = valid_speed(data)
    result = "pass" if actual == expected else "FAIL"
    print(f"test {number}: {data!r} expected {expected}, got {actual}: {result}")

The hint students can ask for: The boundary is wrong: the lowest and highest allowed values should pass. Then add tests of your own, each a pair of an input and the answer you expect, including one that should be refused.

A solution

from bugbot import *
connect()
def valid_speed(text):
    """True if text is a whole number from 0 to 100."""
    return text.isdigit() and 0 <= int(text) <= 100

tests = [("50", True), ("0", True), ("100", True), ("101", False), ("-5", False), ("fast", False)]
tests.append(("75", True))
tests.append(("12.5", False))

for number, (data, expected) in enumerate(tests, start=1):
    actual = valid_speed(data)
    result = "pass" if actual == expected else "FAIL"
    print(f"test {number}: {data!r} expected {expected}, got {actual}: {result}")

Any program that meets the task's checks is marked correct in the simulator; this is one way, not the only way.