Output from scalatest is not synchronized with output from the tests - scalatest

Question

I have a suite of scalatest tests that output information to the console using println as they run.
When I run the suite using the Eclipse Scala plug-in (using Run As ... / 3 ScalaTest - File from the context menu) there is additional output to the console about which tests pass and which fail. I guess this output is from the runner.
The problem is that the lines from my code and the lines from the runner are not interleaved sensibly. It's as if they are being printed from two different threads that aren't synchronized.
For example here is the output from a run
>>>>>>>>>>>>>Starting The parser should warn when the interface name at the end does not match >>>>>>>>>>>>>>>>>>
(interface Fred
interface Bob)
-----------------------------
File: <unknown> line: 2 column: 11 Name does not match.
----The AST after parsing-------------
[ IntfDeclNd( (), (), () ) ]
---------------------------------------
<<<<<<<<<<<<<Finished The parser should warn when the interface name at the end does not match <<<<<<<<<<<<<<<<<
>>>>>>>>>>>>>Starting The parser should parse a class with generic args >>>>>>>>>>>>>>>>>>
(class Fred{type a, type b extends B}() class)
- should parse multiline comment at end of file *** FAILED ***
Expected 0, but got 1 (TestsBase.scala:103)
- should fail on incomplete multiline comment
- should parse single line comments
- should allow a class name to be repeated at the end
- should warn when the class name at the end does not match
- should allow an interface name to be repeated at the end
- should warn when the interface name at the end does not match
----The AST after parsing-------------
The lines starting with "- should" or "Expected" come from the runner and you can see that a bunch of them are plunked in the middle of the output from one of my tests. Other output from the runner appears elsewhere, this isn't all of it.
My questions: Why is this happening? Is there some way to get the runner's output to coordinate with my output?

Answer 1

Most likely, the suites are running in parallel.
http://www.scalatest.org/user_guide/using_the_runner#executingSuitesInParallel
With the proliferation of multi-core architectures, and the often
parallelizable nature of tests, it is useful to be able to run tests
in parallel. [...]
The -P option may optionally be appended with a number (e.g. "-P10" --
no intervening space) to specify the number of threads to be created
in the thread pool. If no number (or 0) is specified, the number of
threads will be decided based on the number of processors available.
So basically pass -P1 to the runner. For eclipse, the place would possibly be the Arguments tab.