ScalaTest: How to print debug output in tests (to STDOUT)

When using ScalaTest, Scala, and SBT, and you want to print output in a ScalaTest unit test that you can see, such as printing to STDOUT with println, I just found out that I can do it using its info function, like this:

test("hello world") {
    info("HELLO WORLD")
    assert(1 == 1)

Now when you run your ScalaTest unit tests with SBT, you’ll see that HELLO WORLD output mixed in with your other ScalaTest output.

As more of a real-world need for this, I just used this technique to print the value of System.getProperty("user.dir") from inside a ScalaTest unit test, so I could be sure where my tests were running.

So while println and System.err.println don’t work for printing output to STDOUT or STDERR, this ScalaTest info function does print output, which is nice.