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Below are the steps to assign build to a test cases.
Click on the Set Your Build button at the right corner of the screen.
You can see that all the test cases are selected by default. Unselect the test cases to which you do not want to apply the build.
Open the Select Build drop-down and select the build you want the selected test cases to be executed against. This list contains all the builds that are linked to release and cycle, which are associated with the test execution that is being carried out.
The Build is set for those test cases that are selected while choosing the build.
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