Test Runner tab in IntelliJ 2018.3 CE not showing

I'm using IntelliJ 2018.3 CE. I have a java maven project (developed using springboot) in which the JUnit tests have already been written. However, when I try to run the tests, the output is always shown in the default run window, and NOT in the Test Runner Tab. In fact, I cannot make this window pop-up after a running a test.

I have Junit 4.12 in the external libraries of my project (as Maven: junit:junit:4.12). The test folders have been appropriately flagged as test resources.

I presume it has to deal with settings in IntelliJ but even with all the effort in the world, I wasn't able to find what is causing this.

Is someone experiencing the same issue? Or does someone know how to resolve this?

Any help would be very much appreciated.