Overview

In specific scenarios, system allows user to define what parameter values can never be tested together or in the other hand, scenarios where paramater values can only be tested together. 
For that, user can apply contraints to support these cases.

Invalid constraints

Invalid constraints restrict parameter values that can never be tested together.

In this example, let's assume Internet Explorer (IE) is not supported on Apple computers so it would be impossible for a tester to execute a test case that instructed them to launch IE from a Mac running on its native operating system. Accordingly, we do not want any tests generated to include combinations such as “OS X” and “IE8” in the same test case.

On the Rules ->Constraints screen, you will need to click on two red X’s. Hover over the first Value of the Invalid Pair and click on the red X that appears

Find the second Value that can never appear together with the first one, hover over it, and click on the red X to create your “Invalid Pair”

As you enter your Constraints, you will see them listed to the left:

Problem solved!

After you enter these two Invalid Pairs, clicking on the “Scenarios” button will create a completely new set of test cases that excludes those two pairs of Values (and only those two pairs of Values). Each test with ‘OS X’ as the operating system will have a browser other than IE.

As you use the Invalid Pair feature and the related Bound Pair one, keep in mind these usage tips:

Do you need to add a lot of Invalid Constraints?

• Imagine you had an application that asked “Would you like to add a hotel to your travel reservation?” Any scenarios with “Do Not Add a Hotel” would require many, many different Invalid Constraints between things like “Do Not Add a Hotel” and “Hotel Chain Preference = X”. For situations like those, the Bound Constraint feature will help you accomplish your constraint handling much faster.
• If you have more than 10 or so Invalid Constraints (or Bound Constraints) in your plan, you might find that it is faster to export your plan into Excel and document your paired values in Excel. If so, make sure to both (1) add multiple paired values in DesignWise before you export into Excel (so you can copy and paste the DesignWise formatting for Invalid Constraints and/or Bound Constraints), and (2) ensure that you use the exact spelling of Values (e.g., ‘cutting and pasting’ Values will usually be safer than typing)
  
  

Watch out for “Not Applicable” Values.

• Do you need to add some of them to your plan? Do you need to invalidate the combination of “Not Applicable” with other specific Values?
• Especially watch out for situations where you have multiple related “Not Applicable” values in a plan. Would it make sense to create a “Bound Constraint” between ‘Hotel Chain Preference = Not Applicable’ and ‘Type of Room’ = Not Applicable’?

Bound constraints

Bound constraints restrict parameter values that can only be tested together.