class MyClass {
async myMethod(req, res):Promise<any>{
const result = await new Helper().doSomething()
}
}
When creating a unit test for myMethod, how can we mock the Helper class method?
class MyClass {
async myMethod(req, res):Promise<any>{
const result = await new Helper().doSomething()
}
}
When creating a unit test for myMethod, how can we mock the Helper class method?
If you haven't specified the testing package you're using, here is a solution using Jest.
To create a manual mock, save a mock implementation in the mocks folder. This allows for specifying the implementation and using it across test files.
// __mocks__/HelperClass.js
// Import this named export into your test file:
export const mockRandomMethod = jest.fn();
const mock = jest.fn().mockImplementation(() => {
return {randomMethod: mockRandomMethod};
});
export default mock;
Import the mock and the shared mock method:
// myMainClass.test.js
import HelperClass, {mockRandomMethod} from './HelperClass';
import myMainClass from './myMainClass';
jest.mock('./HelperClass'); // HelperClass now acts as a mock constructor
beforeEach(() => {
// Clear all instances and calls to constructor and methods:
HelperClass.mockClear();
mockRandomMethod.mockClear();
});
it('Verify if the consumer called a method on the class instance', () => {
const myMainClassInstance = new myMainClass();
myMainClassInstance.sampleMethod();
expect(mockRandomMethod).toHaveBeenCalled();
});
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