使用Jest测试打字稿异步功能

Question

I have the following code in main typescript file:

public readonly funcname = async (param: string): Promise<CustomeType> => {
    const constname = somefunction(strparam, jsonparam);
    return Promise.resolve({
        reqname:constname
    });
};

This is written under an exported class say exportedservice.

I am writing the following testcase in jest for same:

const outputMock = jest.fn(() => {
    return Promise.reject();
});

const exportedserviceobj = new exportedservice();

describe('Statement', () => {
    it('statement', async () => {
        expect.assertions(1);
        const outputResult = await exportedserviceobj.funcname('TestFile');
        outputMock().then(outputResult);
        expect(outputResult).toEqual('undefined');
    });
});

while running the test case; it is throwing a type error:

exportedservice.funcname is not a function

As I am new to typescript; so after a lot of R&D; I am unable to resolve the issue. Please suggest appropriate way to solve this out. Thanks in Advance.

Answer 1

You have to mock exportedservice. For example:

import * as Exportedservice from './exportedservice'
jest.mock('./exportedservice')
describe('Statement', () => {
it('statement', async () => {
    Exportedserviceobj.funcname = jest.fn().mockResolvedValue('test');
    const outputResult = await Exportedserviceobj.funcname('TestFile');
    expect(outputResult).toEqual('test');
});

});