fix(shuffle): fix shuffle methode for array with length <= 1

src/common/utils/shuffle.js

@@ -5,12 +5,15 @@ function rndNext(min, max) {
 }
 
 function shuffle (arr, from, to) {
-  if (!to) {
-    to = arr.length - 1;
+  if (arr.length <= 1){
+    return arr;
   }
   if (!from) {
     from = 0;
   }
+  if (!to) {
+    to = arr.length - 1;
+  }
   const newArr = [...arr];
   if (from >= to) return;
   for (var current = from; current <= to; ++current) {

test/unit/common/utils/shuffle.test.js

@@ -0,0 +1,75 @@
+const shuffle = require('../../../../src/common/utils/shuffle');
+
+describe('shuffle', () => {
+  test('Should return a shuffle array (same size, different order)', async () => {
+    // arrange
+    const tArray = [1,2,3,4,5,6,7,8,9];
+    // act
+    const result = shuffle(tArray);
+    // assert
+    expect(result).toHaveLength(tArray.length);
+    expect(result).not.toEqual(tArray);
+  });
+
+  test('Should return a shuffle array for array of size 1', async () => {
+    // arrange
+    const tArray = [1];
+    // act
+    const result = shuffle(tArray);
+    // assert
+    expect(result).toHaveLength(tArray.length);
+    expect(result).toEqual(tArray);
+  });
+
+  test('Should return a shuffle array for array of size 0', async () => {
+    // arrange
+    const tArray = [];
+    // act
+    const result = shuffle(tArray);
+    // assert
+    expect(result).toHaveLength(tArray.length);
+    expect(result).toEqual(tArray);
+  });
+  
+  test('Should return a shuffle only from a starting point', async () => {
+    // arrange
+    const tArray = [1,2,3,4,5,6,7,8,9];
+    // act
+    const result = shuffle(tArray, 2);
+    // assert
+    expect(result).toHaveLength(tArray.length);
+    expect(result).not.toEqual(tArray);
+    const fixedOrigin = [...tArray].splice(0, 2);
+    const shuffledOrigin = [...tArray].splice(2);
+    const fixedResult= [...result].splice(0, 2);
+    const shuffledResult = [...result].splice(2);
+    expect(fixedResult).toHaveLength(fixedOrigin.length);
+    expect(fixedResult).toEqual(fixedOrigin);
+    expect(shuffledResult).toHaveLength(shuffledOrigin.length);
+    expect(shuffledResult).not.toEqual(shuffledOrigin);
+  });
+  
+  test('Should return a shuffle only from a starting point to and end point', async () => {
+    // arrange
+    const tArray = [1,2,3,4,5,6,7,8,9];
+    // act
+    const result = shuffle(tArray, 2, 4);
+    // assert
+    expect(result).toHaveLength(tArray.length);
+    expect(result).not.toEqual(tArray);
+    const fixedStartOrigin = [...tArray].splice(0, 2);
+    const fixedEndOrigin = [...tArray].splice(4);
+    const shuffledOrigin = [...tArray].splice(2, 4);
+    const fixedStartResult= [...result].splice(0, 2);
+    const fixedEndResult = [...tArray].splice(4);
+    const shuffledResult = [...result].splice(2, 4);
+    expect(fixedStartResult).toHaveLength(fixedStartOrigin.length);
+    expect(fixedStartResult).toEqual(fixedStartOrigin);
+    
+    expect(fixedEndResult).toHaveLength(fixedEndOrigin.length);
+    expect(fixedEndResult).toEqual(fixedEndOrigin);
+
+    expect(shuffledResult).toHaveLength(shuffledOrigin.length);
+    expect(shuffledResult).not.toEqual(shuffledOrigin);
+  });
+});