fix: add specific test for string type index at getPrivateKey.js

packages/vvisp-utils/test/getPrivateKey.test.js

@@ -29,14 +29,18 @@ describe('# getPrivateKey test', function() {
       });
     });
 
-    it('should reject when index is not number or number string except undefined and null', function() {
-      expect(() => getPrivateKey(MNEMONIC, '123')).to.not.throw(TypeError);
+    it('should reject with invalid type: JSON or array', function() {
       expect(() => getPrivateKey(MNEMONIC, { a: 1 })).to.throw(TypeError);
       expect(() => getPrivateKey(MNEMONIC, ['hello', 'there'])).to.throw(
         TypeError
       );
     });
 
+    it('should success getPrivateKey with number or number string', function() {
+      expect(() => getPrivateKey(MNEMONIC, '123')).to.not.throw();
+      expect(() => getPrivateKey(MNEMONIC, 123)).to.not.throw();
+    });
+
     it('should set 0 when index is undefined or null', function() {
       const nullIndex = getPrivateKey(MNEMONIC, null);
       const undefinedIndex = getPrivateKey(MNEMONIC, undefined);
@@ -64,6 +68,12 @@ describe('# getPrivateKey test', function() {
       const result1 = getPrivateKey(MNEMONIC, 1);
       result0.should.not.equal(result1);
     });
+
+    it('should be same with string index and number index', function() {
+      getPrivateKey(MNEMONIC, '123').should.be.equal(
+        getPrivateKey(MNEMONIC, 123)
+      );
+    });
   });
 
   describe('private key enable', function() {