diff --git a/app/src/main/java/sudoku/Solver.java b/app/src/main/java/sudoku/Solver.java
index 4eb977c..f1b9249 100644
--- a/app/src/main/java/sudoku/Solver.java
+++ b/app/src/main/java/sudoku/Solver.java
@@ -10,6 +10,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public void setBoard(int[][] board) {
         this.board = board;
     }
@@ -17,6 +18,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public int[][] getBoard() {
         return board;
     }
@@ -24,6 +26,7 @@ public class Solver implements SudokuSolver {
     /**
      * Resets the board to all zeros
      */
+    @Override
     public void clear() {
         board = new int[9][9];
     }
@@ -31,6 +34,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public boolean solve() {
         return solve(0, 0);
     }
@@ -79,6 +83,7 @@ public class Solver implements SudokuSolver {
     /**
      * Randomizes the board. This guarantees a solvable board.
      */
+    @Override
     public void randomizeBoard() {
         this.clear();
         for (int i = 0; i < 9; ++i) {
@@ -94,6 +99,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public void set(int row, int col, int val) {
         if (row < 9 && col < 9) {
             board[row][col] = val;
@@ -103,6 +109,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public int get(int row, int col) {
         if (row < 9 && col < 9) {
             return board[row][col];
@@ -113,6 +120,7 @@ public class Solver implements SudokuSolver {
     /**
      * {@inheritDoc}
      */
+    @Override
     public boolean isLegal(int row, int col, int val) {
         if (row < 0 || row >= 9 || col < 0 || col >= 9 || val < 1 || val > 9) {
             return false;
@@ -153,6 +161,7 @@ public class Solver implements SudokuSolver {
      * 
      * @return true if solved
      */
+    @Override
     public boolean isSolved() {
         return isSolved(0, 0);
     }
diff --git a/app/src/main/java/sudoku/SudokuSolver.java b/app/src/main/java/sudoku/SudokuSolver.java
index e77ecdd..f6fd74b 100644
--- a/app/src/main/java/sudoku/SudokuSolver.java
+++ b/app/src/main/java/sudoku/SudokuSolver.java
@@ -7,7 +7,7 @@ public interface SudokuSolver {
      * @param board a board to copy values from
      * @throws IllegalArgumentException if board is invalid, e.g. not 9x9
      */
-    void setBoard(int[][] board);
+    void setBoard(int[][] board) throws IllegalArgumentException;
 
     /**
      * Get a copy of the sudoku board
@@ -49,6 +49,18 @@ public interface SudokuSolver {
      */
     void set(int row, int col, int nbr);
 
+    /**
+     * Randomize the board. Guaranteed to be solvable.
+     */
+    void randomizeBoard();
+
+    /**
+     * Check if the board is solved
+     * 
+     * @return true if solved
+     */
+    boolean isSolved();
+
     /**
      * Clear the board
      */