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1. ## How many combinations?

Hi

Sorry if this is in the wrong section but as it is a web application I am testing, I thought it would be OK in here. Please feel free to move it if not.

OK to my problem ...

I need to know how to work out the test cases required to give full coverage to a problem I have.

The scenario is as follows ...

A person has 2 eyes, and they can have a maximum of 4 injections in either eye at any one time, but the system also allows injections to be swapped if there has been an error from the left eye to the right eye and vice versa.

How would I work out how many combinations I need to test?

I hope this makes sense. It does in my head but that is not saying much [img]/images/graemlins/crazy.gif[/img]

PNE

2. ## Re: How many combinations?

Is this an interview question?
An exam?

3. ## Re: How many combinations?

Hi Joe

I can say honestly say hand on heart that this is a real issue I am having where I work. I had a 'discussion' with the 'powers that be' and said in my opinion there would be a lot combinations to this problem in order to give full coverage.

Do you agree? and if so how would I work out how many?

Thanks again

PNE

4. ## Re: How many combinations?

Your scenario isn't clear enough for me to count the cases.
- does "in either eye" mean you can't have injections in both eyes?
- does "at any one time" mean you need to consider "multiple times"?
- I don't understand the scenario of "allows injections to be swapped..."

But, if I understand your requirements, I think you can start to analyze this way, where L = left, and R = right:
- no injections
- L
- LL
- LLL
- LLLL
- R
- RR
- RRR
- RRRR
- LR (is this possible? not clear from your description)
- etc, etc.

can you extend the list?

5. ## Re: How many combinations?

Q. does "in either eye" mean you can't have injections in both eyes?
A. No, the person can have injections in the right and left eye at the same time

Q. does "at any one time" mean you need to consider "multiple times"?
A. No, what I was trying say is that the person can have a maximum of 4 injections in their left eye and a maximum of 4 injections in their right eye

Q. I don't understand the scenario of "allows injections to be swapped
A. An example would be if the person entered an injecton into the left eye instead of the right eye, the system allows you to 'edit" that injection to change it from the left to the right eye.

Do these answers make it any clearer? Does it change your thought process?

6. ## Re: How many combinations?

Got it.

So can you extend the list now?

7. ## Re: How many combinations?

Do you imagine the list continuing as follows ...

LRR
LRRR
LRRRR
LLR
LLRR
LLRRR
LLRRRR
etc, etc

If so, yes I can extend the list.

As you can see there will be lots of combinations. So what would be the most efficient way of testing this cos surely I wouldn't test all these different combinations or would I?

8. ## Re: How many combinations?

[ QUOTE ]
Do you imagine the list continuing as follows ...

LRR
LRRR
LRRRR
LLR
LLRR
LLRRR
LLRRRR
etc, etc

If so, yes I can extend the list.

[/ QUOTE ]

That's my guess. Then you would need to add the "edit" scenarios as well.

[ QUOTE ]
surely I wouldn't test all these different combinations or would I?

[/ QUOTE ]
Why not?

9. ## Re: How many combinations?

As long as I am on the right track, and yes I agree the 'edit' scenarios will need to be added.

Would you deem it necessary to test all the different combinations if you were testing this?

10. ## Re: How many combinations?

[ QUOTE ]
Would you deem it necessary to test all the different combinations if you were testing this?

[/ QUOTE ]

There's no way for me to tell without a lot more details. But when I see the words "injection" and "eye" in the same sentence, I tend to worry.

Is this a medical application?
What is the risk of NOT testing all combinations?
What is the downside of testing every combination?
How dependent/independent are the combinations?
How much time do you have?
What's the risk if it takes longer than planned?
etc, etc.

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