Explictly state what to submit.

01-tree_successor/task.md

@@ -7,4 +7,5 @@ and it should return another node of the tree with the next higher key
 - The given node can also be a null pointer, in which case the method should
   return the smallest node in the tree.
 
-You should submit the file `tree_successor.*`.
+You should submit the file `tree_successor.*` (but not the
+`tree_successor_test.*`).

02-splay_operation/task.md

@@ -2,3 +2,6 @@ Given an implementation of a binary search tree including parent pointers:
 - implement `splay` method, possibly utilizing the provided `rotate` operation
   performing a single rotation;
 - update `lookup`, `insert` and `remove` methods to utilize it correctly.
+
+You should submit the `splay_operation.*` file (but not the
+`splay_operation_test.*`).