added tests for selecting nodes and getting a subset of packages

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
added test for all nodes if no package was selected

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
added test for selecting a package and getting a subset of nodes

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>