DOC: How-to run tests.

doc/devel/Development.md

+---
+title: Development
+author: Daniel Hornung
+...
+
+
+# Developing the CaosDB server #
+This file contains information about server development, it is aimed at those
+who want to debug, understand or enhance the CaosDB server.
+
+## Testing ##
+Whether developing new features, refacturing code or fixing bugs, the server
+code should be thoroughly tested for correct and incorrect behvaiour, on correct
+and incorrect input.
+
+### Writing tests ###
+Tests go into `src/test/java/caosdb/`, the files there can serve as examples for
+writing tests.
+
+### Running tests with Maven ###
+- Automatic testing can be done with `make test` or, after compilation, `mvn
+  test`.
+- Tests of single modules can be started with `mvn test -Dtest=TextClass`