在 jestjs 中模拟嵌套函数

Question

我有一个非常复杂的对象，我用它来模拟 DataTable() 对象以进行测试。

const obj = {
  DataTable: () => {
    return {
      columns: () => {
        return {
          data: () => {
            return {
              eq: () => {
                return {
                  indexOf: jest.fn(),
                };
              },
            };
          },
          visible: () => {
            return jest.fn();
          },
        };
      },
    };
  },
};

在我的测试代码中，我试图监视其中一些函数，但它总是返回未定义。有没有办法模拟深层嵌套函数的返回值？

    jest.spyOn(obj.DataTable().columns().data().eq(), 'indexOf').mockReturnValue('test');
    console.log(obj.DataTable().columns().data().eq().indexOf()); // returns undefined, should return 'test'

Answer 1

这是单元测试解决方案：

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index.ts:

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import { obj } from \'./obj\';\n\nexport function main() {\n  return obj.DataTable().columns().data().eq().indexOf();\n}\n

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obj.ts:

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export const obj = {\n  DataTable: () => {\n    return {\n      columns: () => {\n        return {\n          data: () => {\n            return {\n              eq: () => {\n                return {\n                  indexOf: () => \'real data\',\n                };\n              },\n            };\n          },\n        };\n      },\n    };\n  },\n};\n

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index.test.ts:

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import { main } from \'./\';\nimport { obj } from \'./obj\';\n\ndescribe(\'61396089\', () => {\n  afterEach(() => {\n    jest.restoreAllMocks();\n  });\n  it(\'should pass\', () => {\n    const mockDataTable = {\n      columns: jest.fn().mockReturnThis(),\n      data: jest.fn().mockReturnThis(),\n      eq: jest.fn().mockReturnThis(),\n      indexOf: jest.fn().mockReturnValueOnce(\'fake data\'),\n    };\n    jest.spyOn(obj, \'DataTable\').mockImplementationOnce(() => mockDataTable);\n    const actual = main();\n    expect(actual).toBe(\'fake data\');\n    expect(mockDataTable.columns).toBeCalledTimes(1);\n    expect(mockDataTable.data).toBeCalledTimes(1);\n    expect(mockDataTable.eq).toBeCalledTimes(1);\n    expect(mockDataTable.indexOf).toBeCalledTimes(1);\n  });\n});\n

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带有覆盖率报告的单元测试结果：

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 PASS  stackoverflow/61396089/index.test.ts (20.978s)\n  61396089\n    \xe2\x9c\x93 should pass (8ms)\n\n----------|---------|----------|---------|---------|-------------------\nFile      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s \n----------|---------|----------|---------|---------|-------------------\nAll files |   44.44 |      100 |   16.67 |   44.44 |                   \n index.ts |     100 |      100 |     100 |     100 |                   \n obj.ts   |   16.67 |      100 |       0 |   16.67 | 3-10              \n----------|---------|----------|---------|---------|-------------------\nTest Suites: 1 passed, 1 total\nTests:       1 passed, 1 total\nSnapshots:   0 total\nTime:        23.889s\n

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源代码：https://github.com/mrdulin/react-apollo-graphql-starter-kit/tree/master/stackoverflow/61396089

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