| b69ab31 | | | 1 | /** |
| b69ab31 | | | 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| b69ab31 | | | 3 | * |
| b69ab31 | | | 4 | * This source code is licensed under the MIT license found in the |
| b69ab31 | | | 5 | * LICENSE file in the root directory of this source tree. |
| b69ab31 | | | 6 | */ |
| b69ab31 | | | 7 | |
| b69ab31 | | | 8 | import lazyInit from '../lazyInit'; |
| b69ab31 | | | 9 | |
| b69ab31 | | | 10 | describe('lazyInit', () => { |
| b69ab31 | | | 11 | test('async operation never called', () => { |
| b69ab31 | | | 12 | let numCalls = 0; |
| b69ab31 | | | 13 | let theObject; |
| b69ab31 | | | 14 | function expensiveObjCreation() { |
| b69ab31 | | | 15 | ++numCalls; |
| b69ab31 | | | 16 | theObject = {}; |
| b69ab31 | | | 17 | return Promise.resolve(theObject); |
| b69ab31 | | | 18 | } |
| b69ab31 | | | 19 | |
| b69ab31 | | | 20 | const getObj = lazyInit(expensiveObjCreation); |
| b69ab31 | | | 21 | expect(typeof getObj).toBe('function'); |
| b69ab31 | | | 22 | expect(theObject).toBe(undefined); |
| b69ab31 | | | 23 | expect(numCalls).toBe(0); |
| b69ab31 | | | 24 | }); |
| b69ab31 | | | 25 | |
| b69ab31 | | | 26 | test('async operation called when value requested', async () => { |
| b69ab31 | | | 27 | let numCalls = 0; |
| b69ab31 | | | 28 | let theObject; |
| b69ab31 | | | 29 | function expensiveObjCreation() { |
| b69ab31 | | | 30 | ++numCalls; |
| b69ab31 | | | 31 | theObject = {}; |
| b69ab31 | | | 32 | return Promise.resolve(theObject); |
| b69ab31 | | | 33 | } |
| b69ab31 | | | 34 | |
| b69ab31 | | | 35 | const getObj = lazyInit(expensiveObjCreation); |
| b69ab31 | | | 36 | expect(numCalls).toBe(0); |
| b69ab31 | | | 37 | const obj = await getObj(); |
| b69ab31 | | | 38 | expect(numCalls).toBe(1); |
| b69ab31 | | | 39 | expect(obj).toBe(theObject); |
| b69ab31 | | | 40 | }); |
| b69ab31 | | | 41 | |
| b69ab31 | | | 42 | test('async operation called only once when value requested many times', async () => { |
| b69ab31 | | | 43 | let numCalls = 0; |
| b69ab31 | | | 44 | let theObject; |
| b69ab31 | | | 45 | function expensiveObjCreation() { |
| b69ab31 | | | 46 | ++numCalls; |
| b69ab31 | | | 47 | theObject = {}; |
| b69ab31 | | | 48 | return Promise.resolve(theObject); |
| b69ab31 | | | 49 | } |
| b69ab31 | | | 50 | |
| b69ab31 | | | 51 | const getObj = lazyInit(expensiveObjCreation); |
| b69ab31 | | | 52 | expect(numCalls).toBe(0); |
| b69ab31 | | | 53 | |
| b69ab31 | | | 54 | const obj1 = await getObj(); |
| b69ab31 | | | 55 | const obj2 = await getObj(); |
| b69ab31 | | | 56 | const obj3 = await getObj(); |
| b69ab31 | | | 57 | expect(numCalls).toBe(1); |
| b69ab31 | | | 58 | expect(obj1).toBe(theObject); |
| b69ab31 | | | 59 | expect(obj2).toBe(theObject); |
| b69ab31 | | | 60 | expect(obj3).toBe(theObject); |
| b69ab31 | | | 61 | }); |
| b69ab31 | | | 62 | }); |