Correctly mock date.constructor (#28)

* Correctly mock date.constructor

* Add more test cases

* test: change travis to github action (#29)

---------

Co-authored-by: hustcc <i@hust.cc>

__tests__/index.js

@@ -15,16 +15,24 @@ describe('jest-date-mock', () => {
     // Date isEqual
     expect(new Date()).toEqual(new Date(0));
 
+    // .constructor()
+    expect(+new Date(1000).constructor()).toBe(0);
+    expect(+new Date().constructor(10000)).toBe(10000);
+    expect(new Date().constructor(10000)).toBeInstanceOf(Date);
+
+
     // +
     expect(+new Date()).toBe(0);
     expect(+new Date(10000)).toBe(10000);
 
+
     // getTime
     expect(new Date().getTime()).toBe(0);
     expect(new Date(10000).getTime()).toBe(10000);
 
     // instanceof
     expect(new Date()).toBeInstanceOf(Date);
+    expect(new Date().constructor(10000)).toBeInstanceOf(Date);
 
     // 2018-05-27 08:00:00
     expect(new Date(Date.UTC(2018, 5, 27, 0, 0, 0)).getTime()).toBe(1530057600000);
@@ -91,6 +99,9 @@ describe('jest-date-mock', () => {
     expect(+new Date() - now).toBe(0);
     advanceBy();
     expect(+new Date() - now).toBe(0);
+
+    advanceBy(3000);
+    expect(+new Date().constructor() - now).toBe(3000); // .constructor()
   });
 
   test('clear', () => {
@@ -99,6 +110,7 @@ describe('jest-date-mock', () => {
 
     advanceTo();
     expect(+new Date()).toBe(0);
+    expect(+new Date().constructor()).toBe(0);
   });
 
   test('usage', () => {

src/mockDate.js

@@ -13,6 +13,7 @@ export const mockDateClass = D => {
     const dateArgs = args.length === 0 ? [mockNow()] : args;
     const instance = new D(...dateArgs);
     Object.setPrototypeOf(instance, Object.getPrototypeOf(this));
+    instance.constructor = Date;
     return instance;
   }