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unit-testing - 尝试使用 Jest 模拟 fs.readFileSync 时出错

问题描述

这是我的测试文件：

const request  = require('supertest');
const app = require('../../src/app');
const fs = require('fs');

jest.mock('fs');

describe('Get Accounts Info', () => {
    it('Get Accounts Info', async () => {
      fs.readFileSync.mockResolvedValue({ message: 'Test'})
      const res = await request(app).get('/accounts')
    });
  });

但是，当我尝试运行 by:npm test -- routes.test.js -t "Get Accounts Info"时，会出现错误：

<--- Last few GCs --->

[20668:0000020C15EF9CD0]    82511 ms: Mark-sweep (reduce) 2047.1 (2050.7) -> 2046.4 (2051.9) MB, 4231.6 / 0.0 ms  (+ 0.0 ms in 2 steps since start of marking, biggest step 0.0 ms, walltime since start of marking 4232 ms) (average mu = 0.113, current mu = [20668:0000020C15EF9CD0]    88662 ms: Mark-sweep (reduce) 2046.7 (2050.9) -> 2046.5 (2052.2) 
MB, 5331.4 / 0.0 ms  (+ 0.0 ms in 5 steps since start of marking, biggest step 0.0 ms, walltime since start of marking 6150 ms) (average mu = 0.124, current mu = 

<--- JS stacktrace --->

FATAL ERROR: MarkCompactCollector: young object promotion failed Allocation failed - JavaScript heap out of memory
 1: 00007FF7BD3A4C6F napi_wrap+111007
 2: 00007FF7BD3481F6 v8::base::CPU::has_sse+59910
 3: 00007FF7BD3490F6 node::OnFatalError+294
 4: 00007FF7BDC2220E v8::Isolate::ReportExternalAllocationLimitReached+94
 5: 00007FF7BDC06FDD v8::SharedArrayBuffer::Externalize+781
 6: 00007FF7BDAB011C v8::internal::Heap::EphemeronKeyWriteBarrierFromCode+1516
 7: 00007FF7BDA9AB9B v8::internal::NativeContextInferrer::Infer+59739
 8: 00007FF7BDA7FE6F v8::internal::MarkingWorklists::SwitchToContextSlow+56975
 9: 00007FF7BDA93B5B v8::internal::NativeContextInferrer::Infer+31003
10: 00007FF7BDA8AC3D v8::internal::MarkCompactCollector::EnsureSweepingCompleted+6285
11: 00007FF7BDA92DAE v8::internal::NativeContextInferrer::Infer+27502
12: 00007FF7BDA96DFB v8::internal::NativeContextInferrer::Infer+43963
13: 00007FF7BDAA07F2 v8::internal::ItemParallelJob::Task::RunInternal+18
14: 00007FF7BDAA0781 v8::internal::ItemParallelJob::Run+641

如何修复或模拟fs.readFileSync？

标签： unit-testingjestjs

解决方案

我更喜欢只模拟我将要使用的方法，如下所示；

jest.spyOn(fs, 'readFileSync').mockImplementation(function () {
    // Whatever you want to return. In your case, maybe a promise.
});

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