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You need to run the ant setup target to copy jar files to their appropriate home in classpath. Do this by right-clicking on setup in the Outline view and selecting Run->Ant Build.
These will leave you two jar files short.
Add them to the Java build path by right-clicking on the grits project and selecting Properties, then Java Build Path. Add junit and mockobjects.
If you didn't get them in the right place, they are generally to be found in the lib/runtime directory and should be copied into the afore-mentioned lib directory.
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