I decided to try to code up my own test runner to make this work. Here's the first version:
First, the build target concatenates all of the test files. In my case, test files are in a directory called tests and each of them ends with Test.js.
Most of the magic happens in testRunner.js:
Basically how it works is to override some methods in goog.testing.TestCase to capture the results. We don't particularly care about successes, so they're replaced by dots. Failures show as an F and any errors are explained in more detail after all tests finish.
I've uploaded all of the example code to Github at https://github.com/omnicolor/Closure-CLI-test-runner.