From eb99bdc06b1114c4e58b7a1d4007321f02a9d64b Mon Sep 17 00:00:00 2001
From: Roland Hummel <roland.hummel@qaware.de>
Date: Sat, 2 Oct 2021 22:51:25 +0200
Subject: [PATCH 1/3] Add proper test to Backtracking/Sudoku

This replaces the "main" test in the implementation file.
---
 Backtracking/Sudoku.js            | 24 +-------------
 Backtracking/tests/Sudoku.test.js | 52 +++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 23 deletions(-)
 create mode 100644 Backtracking/tests/Sudoku.test.js

diff --git a/Backtracking/Sudoku.js b/Backtracking/Sudoku.js
index ae360bbe2..650758d5b 100644
--- a/Backtracking/Sudoku.js
+++ b/Backtracking/Sudoku.js
@@ -72,26 +72,4 @@ class Sudoku {
   }
 }
 
-function main () {
-  // main function with an example
-  const sudokuBoard = new Sudoku([
-    [3, 0, 6, 5, 0, 8, 4, 0, 0],
-    [5, 2, 0, 0, 0, 0, 0, 0, 0],
-    [0, 8, 7, 0, 0, 0, 0, 3, 1],
-    [0, 0, 3, 0, 1, 0, 0, 8, 0],
-    [9, 0, 0, 8, 6, 3, 0, 0, 5],
-    [0, 5, 0, 0, 9, 0, 6, 0, 0],
-    [1, 3, 0, 0, 0, 0, 2, 5, 0],
-    [0, 0, 0, 0, 0, 0, 0, 7, 4],
-    [0, 0, 5, 2, 0, 6, 3, 0, 0]
-  ])
-
-  sudokuBoard.printBoard()
-
-  console.log('\n')
-  sudokuBoard.solve()
-
-  sudokuBoard.printBoard()
-}
-
-main()
+export { Sudoku }
diff --git a/Backtracking/tests/Sudoku.test.js b/Backtracking/tests/Sudoku.test.js
new file mode 100644
index 000000000..a656d3653
--- /dev/null
+++ b/Backtracking/tests/Sudoku.test.js
@@ -0,0 +1,52 @@
+import { Sudoku } from '../Sudoku'
+
+const data = [
+  [3, 0, 6, 5, 0, 8, 4, 0, 0],
+  [5, 2, 0, 0, 0, 0, 0, 0, 0],
+  [0, 8, 7, 0, 0, 0, 0, 3, 1],
+  [0, 0, 3, 0, 1, 0, 0, 8, 0],
+  [9, 0, 0, 8, 6, 3, 0, 0, 5],
+  [0, 5, 0, 0, 9, 0, 6, 0, 0],
+  [1, 3, 0, 0, 0, 0, 2, 5, 0],
+  [0, 0, 0, 0, 0, 0, 0, 7, 4],
+  [0, 0, 5, 2, 0, 6, 3, 0, 0]
+]
+
+const solved = [
+  [3, 1, 6, 5, 7, 8, 4, 9, 2],
+  [5, 2, 9, 1, 3, 4, 7, 6, 8],
+  [4, 8, 7, 6, 2, 9, 5, 3, 1],
+  [2, 6, 3, 4, 1, 5, 9, 8, 7],
+  [9, 7, 4, 8, 6, 3, 1, 2, 5],
+  [8, 5, 1, 7, 9, 2, 6, 4, 3],
+  [1, 3, 8, 9, 4, 7, 2, 5, 6],
+  [6, 9, 2, 3, 5, 1, 8, 7, 4],
+  [7, 4, 5, 2, 8, 6, 3, 1, 9],
+]
+
+describe('Sudoku', () => {
+  it('should create a valid board successfully', () => {
+    expect(() => {new Sudoku(data)}).not.toThrow()
+  })
+
+  it('should find an empty cell', () => {
+    const board = new Sudoku(data)
+    const emptyCell = board.findEmptyCell()
+    expect(emptyCell).not.toEqual([-1, -1])
+  })
+
+  it('should solve the board successfully', () => {
+    const board = new Sudoku(data)
+    board.solve()
+
+    // should not have empty cells anymore
+    const emptyCell = board.findEmptyCell()
+    expect(emptyCell).toEqual([-1, -1])
+
+    // solved board should match our expectation
+    for (let i = 0; i < 9; i++) {
+      const section = board.getSection(i, [0, 9])
+      expect(section).toEqual(solved[i])
+    }
+  })
+})
\ No newline at end of file

From 44fee4167fb93b4f349a50b033b6aceb5e93f7c7 Mon Sep 17 00:00:00 2001
From: Roland Hummel <roland.hummel@qaware.de>
Date: Sun, 3 Oct 2021 10:15:35 +0200
Subject: [PATCH 2/3] Code style

---
 Backtracking/tests/Sudoku.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Backtracking/tests/Sudoku.test.js b/Backtracking/tests/Sudoku.test.js
index a656d3653..1154bdd85 100644
--- a/Backtracking/tests/Sudoku.test.js
+++ b/Backtracking/tests/Sudoku.test.js
@@ -49,4 +49,4 @@ describe('Sudoku', () => {
       expect(section).toEqual(solved[i])
     }
   })
-})
\ No newline at end of file
+})

From 2b3db6c1d5e810fc9dfd794ce512a2711af6acb1 Mon Sep 17 00:00:00 2001
From: Roland Hummel <roland.hummel@qaware.de>
Date: Sun, 3 Oct 2021 15:11:15 +0200
Subject: [PATCH 3/3] Apply standard code style

---
 Backtracking/tests/Sudoku.test.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Backtracking/tests/Sudoku.test.js b/Backtracking/tests/Sudoku.test.js
index 1154bdd85..092556f1c 100644
--- a/Backtracking/tests/Sudoku.test.js
+++ b/Backtracking/tests/Sudoku.test.js
@@ -21,12 +21,14 @@ const solved = [
   [8, 5, 1, 7, 9, 2, 6, 4, 3],
   [1, 3, 8, 9, 4, 7, 2, 5, 6],
   [6, 9, 2, 3, 5, 1, 8, 7, 4],
-  [7, 4, 5, 2, 8, 6, 3, 1, 9],
+  [7, 4, 5, 2, 8, 6, 3, 1, 9]
 ]
 
 describe('Sudoku', () => {
   it('should create a valid board successfully', () => {
-    expect(() => {new Sudoku(data)}).not.toThrow()
+    // we deliberately want to check whether this constructor call fails or not
+    // eslint-disable-next-line no-new
+    expect(() => { new Sudoku(data) }).not.toThrow()
   })
 
   it('should find an empty cell', () => {