Complete Example for you to try
(will take 5 minutes from start to end - everything you need is here).

Step 0: Download and install the tool (download page)
Step 1: Download and extract - JAMExample.zip (contains folders/files for example)
Step 2: Run the Jamtester Teacher Tool (from Windows Start menu)
Step 3: click the first "Browse..." button and select the "folder of student folders" folder and open
Step 4: click the second "Browse..." button and select the "SomeClassTest.java" file in the "teacher's test class" folder
Step 6: click the "Add .class/.jar files" button and selecct the "KarelJRobot.jar" file in the "jars needed for example" folder
Step 7: click go and watch it do its thing
Step 8: viewer pops open with results - use the save options to save as .csv or .jam