After adding the following to build.sbt, scalaTest will show a fail summary after the standart report:
testOptions in Test += Tests.Argument("-oI")
I - show reminder of failed and canceled tests without stack traces
T - show reminder of failed and canceled tests with short stack traces
G - show reminder of failed and canceled tests with full stack traces
There is also a "drop TestSucceeded events" flag, but I have failed to use it: http://www.scalatest.org/user_guide/using_the_runner