js: update shuffle solution (typo)

javascript/shuffle/solution.js

@@ -1,10 +1,9 @@
 function shuffle(string) {
     const arr = string.split('');
-    const n = arr.length;
 
-    for(const i = n - 1; i >= 0; i--) {
-        cosnt j = Math.floor(Math.random() * (i + 1));
-        cosnt tmp = arr[i];
+    for(const i = arr.length - 1; i >= 0; i--) {
+        const j = Math.floor(Math.random() * (i + 1));
+        const tmp = arr[i];
         arr[i] = arr[j];
         arr[j] = tmp;
     }
@@ -13,8 +12,19 @@ function shuffle(string) {
 }
 
 // Tests
-/*describe("Solution", function() {
-  it("should shuffle string", function() {
-    Test.assertEquals(shuffle("the quick brown fox jumps over the lazy dog"), '');
+describe("Solution", function() {
+  it("should not be the same string", function() {
+    const str = 'the quick brown fox jumps over the lazy dog';
+    Test.assertNotEquals(shuffle(str), str);
   });
-});*/
+    
+  it("should stay the same string", function() {
+    const str = 'f';
+    Test.assertEquals(shuffle(str), str);
+  });
+
+  it("should shuffle string", function() {
+    const str = 'a b';
+    Test.assertIn(shuffle(str), ['a b', 'b a', ' ba', 'ba ', 'ab ', ' ab']);
+  });
+});