Why do I get 'no possible value' when I create scripts?

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I'm looking to move one product to another but when I Create Scripts, I get scripts which include 'no possible value'. These are not negative scripts. Is it because I reduced options by one and the original options are still in the parameters. How do I delete parameters? 
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Posted 5 years ago

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Photo of Justin Hunter, Hexawise Founder

Justin Hunter, Hexawise Founder, Founder and CEO

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Good questions.


I assume you have some invalid pairs in this test plan? What the "no possible value" is trying to tell you is that the test case is providing coverage for a needed pair, and that the way you have your invalid pairs setup then prevents this test from being able to provide a value for that parameter in light of that needed pair and the invalid pairs. That sounds confusing, I know, so an example is much easier to understand.

Let's say we have a test plan with 3 parameters, each with 2 values:

Fruit: Apple, Pear
Car: Toyota, Dodge
Dog: Collie, Mutt

And let's further suppose we have 2 invalid pairs:

if Fruit = Apple then Car != Toyota
if Car = Dodge then Dog != Mutt

To create 2-way coverage, Hexawise will ensure you've paired every parameter value with every other parameter value (unless an invalid pair says it shouldn't be paired), which in this case means that Hexawise will necessarily pair Fruit as Apple with Dog as Mutt in at least one test case, since that pairing could be the source of a bug. You probably already see the problem!

In the test case that has Fruit as Apple and Dog as Mutt we need to have a test value for the Car parameter. You can't have Car as Toyota, because Apple can't be paired with Toyota, and you can't have Car as Dodge, because Mutt can't be paired with Dodge. So what value can Hexawise provide for Car in this test case? It has no value to provide, there is none, so it provides "no possible value".

That's why you get these cases. Generally, given the real context of your actual test plan, it is clear what to do to resolve these. Sometimes your invalid pairs may need a bit of adjusting, sometimes you might want to introduce a "N/A" value for a parameter, etc.


Editing parameter names is easy. Simply go to the Define Inputs screen and click on the name of a parameter. That will allow you to edit it.


Editing constraints is straightforward too. Simply:

1) Go to the "Define Inputs" screen,
2) Hover over the name of a value,
3) Click on the red X (to add an invalid pair) or green arrows (Married Pair)
4) Again, don't forget that sometimes you might need to add a Value called something like "Not Applicable" to one or more of your Parameters in some of your scenarios.

If you have a real-life case where it's not so clear what to do, let us know and one of us would be more than happy to hop on the phone and talk through that test plan with you.

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Thanks Justin

I've added N/A.

How do I then exclude these tests if I don't want them?
Photo of Justin Hunter, Hexawise Founder

Justin Hunter, Hexawise Founder, Founder and CEO

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Thank you for your question.  You usually would not want to remove the tests that include "N/A" in them.  Where you see an N/A, that is just an indication that the specific value in question is not applicable.  It is not an indication that the entire test scenario should be removed.

A flight reservation example might help to explain this point:

Fly to: USA, China, Australia
Class: First, Business, Economy
Reserve a Car Also: Car, No Car
Type of Car: Luxury, Economy, N/A
Payment Method: Credit Card, Frequent Flyer Miles

Some tests would look like this:

Fly to: USA
Class: Business
Reserve a Car Also: Car
Type of Car: Economy
Payment Method: Credit Card

Other tests would look like this:

Fly to: China
Class: Economy
Reserve a Car Also: No Car
Type of Car: N/A
Payment Method: Frequent Flier Miles

It would be a mistake to remove the second type of test (e.g., tests that include N/A's).  That is because each test in a set of Hexawise-generated set of tests includes important combinations. The test scenario above, for example, might be the only test in the set that contains certain combinations, such as, e.g., 

China and Economy
China and No Car
China and Frequent Flier Miles
Economy and No Car
Economy and Frequent Flyer Miles
No Car and Frequent Flyer Miles

I hope this example helps.  If not, please let us know.  Thank you.

- Justin
Photo of Justin Hunter, Hexawise Founder

Justin Hunter, Hexawise Founder, Founder and CEO

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We have posted a blog post about how to address it when you see No Possible Value in Hexawise that might be helpful: https://hexawise.com/posts/whaddya-mean-no-possible-value