Error starting the test run: Build directory of the test run is not specified or does not exist.
In Microsoft Test and Lab Manager, the above error message is observed during the execution of an automated test run on a test controller. It can occur in either of the following conditions.
1. The account under which test controller is running does not have read permission on the build directory. (The build directory is same as the drop location of build associated with this test run.)
2. The build directory itself does not exist.
So to come out of this error, ensure that build directory exists and test controller service account has read permission on it.