It works, for you

Your booking code works. You typed 10 and it booked the hour.

Now a tester types "abc". Then 9. Then 21. Then nothing at all. Your code stops with an error.

You are the person who knows the code, so you try the easy things. A good tester tries the things that break it.

Key words

Word	What it means	Example
Test plan	A table of tests written before you run them.	hour 21: expect refused
Test data	The values you use in a test.	10, 21, "abc"
Valid data	A value the program should accept.	14
Invalid data	The right kind of value, but not allowed. The program should refuse it.	5
Extreme data	A value at the very edge of the allowed range: the first or the last one.	9 and 20 are valid. 8 and 21 are invalid.
Erroneous data	The wrong kind of value. The program should refuse it.	the word "abc" for an hour
Expected result	What should happen, written before the test.	Refused
Actual result	What really happened.	Booked
Evidence	Proof that you ran the test and what happened.	a screenshot

The cells students fill in are left blank in this preview.

A test plan for the hour check

No.	Purpose	Data	Type	Expected	Actual	Action
1	Accept a sensible hour	14	Valid	Booked
2	Accept the first hour	9	Valid extreme	Booked
3	Accept the last hour	20	Valid extreme	Booked
4	Refuse just too early	8	Invalid extreme	Refused	Booked (wrong)	Change the check to start at 9, then run again
5	Refuse just too late	21	Invalid extreme	Refused
6	Refuse a very wrong hour	5	Invalid	Refused
7	Refuse words	abc	Erroneous	Refused
8	Refuse nothing typed	(empty)	Erroneous	Refused

The cells students fill in are left blank in this preview.

Where the full table is needed

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Task 2 asks for tests with proof: the purpose, the data, what you expect, what happened, and what you do next. Task 4a says a formal test document is not needed there. You must still test, so your product works. Practise the full table here.

Write the expected result first

data-callouts.warning.label

Write what should happen before you run the test. If you write it after, you may write what happened instead. Then every test passes, and the plan shows nothing.

Try it: a test is a small program

Code: python

def valid_hour(text):
    if text.isdigit():
        hour = int(text)
        if hour >= 9 and hour <= 20:
            return hour
    return None


def check(number, data, expected):
    actual = valid_hour(data)
    result = "FAIL"
    if actual == expected:
        result = "PASS"
    print(number, data, "expected", expected, "got", actual, result)


check(1, "14", 14)
check(2, "9", 9)
check(3, "21", None)
check(4, "abc", None)

# isdigit() checks the text is only digits.
# >= means "is more than or equal to". <= means "is less than or equal to".
# Add a test for "8". Run it.