implement SudokuSolver.validate() method and write unit tests for method

controllers/sudoku-solver.js

@@ -8,19 +8,73 @@ class SudokuSolver {
 
     checkRowPlacement(puzzleString, row, column, value) {
 
+        // rows
+        const rows = {
+            A: [],
+            B: [],
+            C: [],
+            D: [],
+            E: [],
+            F: [],
+            G: [],
+            H: [],
+            I: [],
+        };
 
+        // rowKeys
+        const rowKeys = Object.keys(rows);
+
+        // split puzzle strings and assign row values for each row
+        rowKeys.forEach((key, index) => {
+
+            const start = index * 9;
+            const end = start + 9;
+
+            const rowValues = puzzleString.slice(start, end).split('');
+            
+            rows[key] = rowValues
+
+        });
+
+        // get row values for placement
+        const rowValues = rows[row];
+
+        // get existing value placed
+        const existingValue = rowValues[column - 1];
+
+        // make sure placement location does not already contain a number
+        // make sure placements row does not already have value.
+        return (existingValue == '.' || existingValue == value) && !rowValues.includes(value);
 
     }
 
     checkColPlacement(puzzleString, row, column, value) {
 
+        const columns = {
+            1: [],
+            2: [],
+            3: [],
+            4: [],
+            5: [],
+            6: [],
+            7: [],
+            8: [],
+            9: [],
+        };
 
+        const columnKeys = Object.keys(columns);
+
+        columnKeys.forEach((key, index) => {
+
+            
+
+        });
 
     }
 
     checkRegionPlacement(puzzleString, row, column, value) {
 
-        
+
 
     }