Switching the numbers on payday
A firm replaces its wages system on the last Friday of the month. The old one is switched off at noon. The new one has never been tried with real pay data.
It miscounts overtime. Three hundred people are paid the wrong amount.
The plan was fine. The way it was tested and switched on was not.
Key words
| Word | What it means |
|---|---|
| Configuration | setting up a system so it fits the organisation |
| Integration | making separate systems work together |
| Test environment | a safe copy of a system, used to try things out |
| Reproducible | giving the same result each time the test is repeated |
| Parallel | running the old and new systems side by side |
| Phased | switching on a little at a time |
| Direct | stopping the old system and starting the new one at once |
| Pilot | trying the new system with a small group first |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can choose the safest way to put a change into use and say how it must be tested first.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Configure the new system
Configuration sets the new system up for this organisation: its users, rules and settings.
Two things matter most. First, integration with legacy systems, the older systems that must keep working with it. Second, maintaining service: people must still be able to work during the change.
Test before it goes live
A new system must be fully tested before real people rely on it.
Use a test environment: a copy of the real system with the same hardware and software, but with no real customers. Tests must be reproducible: the same steps give the same result each time, so a fault can be found and fixed.
A reproducible test
old_total = 100 + 250 + 75
new_total = 100 + 250 + 75
for attempt in range(3):
if old_total == new_total:
print("Attempt", attempt + 1, "totals match")
else:
print("Attempt", attempt + 1, "totals differ")Check: configuring and testing
Have a go
Check: configuring and testing
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.