updating DIRECTORY.md

Author: github-actions

DIRECTORY.md

@@ -5,6 +5,8 @@
   * [KnightTour](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/KnightTour.js)
   * [NQueen](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/NQueen.js)
   * [Sudoku](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/Sudoku.js)
+  * tests
+    * [NQueen](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/tests/NQueen.test.js)
 
 ## Bit-Manipulation
   * [BinaryCountSetBits](https://github.com/TheAlgorithms/Javascript/blob/master/Bit-Manipulation/BinaryCountSetBits.js)