tests: add missing test for KnightTour (#1598)

Author: vil02

Diff for: Backtracking/tests/KnightTour.test.js

@@ -11,7 +11,7 @@ describe('OpenKnightTour', () => {
       [0, 0, 0, 0, 0]
     ])
 
-    KT.solve()
+    expect(KT.solve()).toBe(true)
     expect(KT.board).toEqual([
       [19, 4, 15, 10, 25],
       [14, 9, 18, 5, 16],
@@ -20,4 +20,18 @@ describe('OpenKnightTour', () => {
       [21, 2, 7, 12, 23]
     ])
   })
+
+  it('OpenKnightTour(2)', () => {
+    const KT = new OpenKnightTour(2)
+    expect(KT.board).toEqual([
+      [0, 0],
+      [0, 0]
+    ])
+
+    expect(KT.solve()).toBe(false)
+    expect(KT.board).toEqual([
+      [0, 0],
+      [0, 0]
+    ])
+  })
 })