CON-3827 add unit test instructions to filler (#3151)

* fix(filler): add unit tests

* fix(filler): add unit tests

Author: pedrodesu

subjects/filler/README.md

@@ -163,6 +163,15 @@ And his response:
 7 2\n
 ```
 
+### Unit Tests
+
+You must implement unit tests within your `filler` project to ensure your robot's parsing logic and placement strategy are reliable. Specifically, your tests should:
+
+- Verify **Input Parsing** by ensuring the Anfield grid and the incoming pieces are correctly converted into internal data structures from the standard input string.
+- Verify **Valid Placement Logic** by testing that a potential coordinate correctly identifies if it has exactly one overlapping cell with existing territory and zero overlaps with the opponent.
+- Test **Boundary Conditions** to ensure the robot never attempts to place a piece that extends beyond the rows or columns of the Anfield.
+- Verify **Coordinate Output** by ensuring the final calculation is formatted exactly as `X Y\n` as required by the `game_engine`.
+
 ### Bonus
 
 - Create a graphic visualizer for this project.

subjects/filler/audit/README.md

@@ -24,6 +24,16 @@
 
 ###### Can you confirm that the student player won at least 4 out of 5 times?
 
+#### Unit Tests
+
+###### Do all tests pass without errors?
+
+###### Are there specific tests for **Input Parsing** (e.g., verifying the robot correctly reads the Anfield dimensions and the piece shape from stdin)?
+
+###### Are there tests for **Placement Validation** (e.g., checking that a move is rejected if it overlaps two of your own cells or one of the opponent's)?
+
+###### Are there tests for **Boundary Detection** to ensure pieces are never placed partially outside the grid?
+
 #### Basic
 
 ###### +Does the code obey the [good practices](../../good-practices/README.md)?