VSTS Maven build - no JUnit tests run - maven

Question

[Update: Problem cause found! read below]
Problem: VSTS Maven build does not seem to run JUnit, does not show any JUnit results, does not seem to produce any JUnit testreports.
In VSTS, we have a Java project with a Contact and TestContact class with 1 testcase;
source\module\src\main\java\nl\customer\model\situation\Contact.java
source\module\src\test\java\nl\customer\model\ContactTest.java
source\module\pom.xml
Running Maven from Eclipse works fine. Console shows Maven using Surefire reports, running/passing the 1 unit test.
Running the project with Maven on a Windows PC also works:
mvn test
Logging:
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Domain Model
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) # module ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 30 resources
[INFO] skip non existing resourceDirectory C:\project\source\projectdomain\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) # module ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) # module ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory C:\project\source\module\src\test\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) # module ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.20.1:test (default-test) # module ---
[INFO]
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running nl.customer.module.ContactTest
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.002 s - in nl.customer.module.ContactTest
[INFO]
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.109 s
[INFO] Finished at: 2018-01-09T14:05:03+01:00
[INFO] Final Memory: 10M/196M
[INFO] ------------------------------------------------------------------------
In VSTS, using the Maven build step (goal: install) succeeds, but the log does not show anything about JUnit, even with system.debug = true.
Consequently, trying the "Publish test results" always fails (both when using a seperate build task or the Publish TFS option in the maven build task).

Answer 1

It seems I have found the cause of the problem: in VSTS, the Maven build task has the option
Set MAVEN_OPTS to
In our build definition, this was set to
-Xmx1024m -X
The first parameter is correct, it sets the maximum memory.
The second parameter is incorrect. If you want Maven to give debug output, you should put the "-X" parameter under Goal(s).
There is no real warning about the second parameter in the logging.