Once the conversion @ MDL-71049 has been finished and all the testcases have a namespace, it's time to look for redundant uses of those namespaces within the test cases code.

For example:

namespace mod_xxx;

...

$something = \mod_xxx\level2\yyy::do();

$anything = new \mod_xxx\zzz();

...

So, for a given namespace (mod_xxx), there aren't uses of it in code (\mod_xxx). Excluding literals and phpdoc blocks.