Steps to Reproduce
1. Create a test.
2. Create an 'Open a new form' step on the 'sc_task' table.
3. Create a 'Click a UI Action' step for the 'Submit' UI action
4. Create another 'Open a new form' step on the 'sc_task' table.
5. Make sure there are no client test runners open.
6. Click the Run Test button, and in the 'Pick a Browser' modal, make sure 'Start a new test runner' radio button is selected. Click Run Test.
Before running the test, open a new client test runner using the Client Test Runner module.
Related Problem: PRB1272093