[英]Mocking up static methods in jest
I am having trouble mocking up a static method in jest.我在开玩笑的 static 方法上遇到了麻烦 mocking。 Immagine you have a class A with a static method:
想象一下你有一个 class A 和一个 static 方法:
export default class A {
f() {
return 'a.f()'
}
static staticF () {
return 'A.staticF()'
}
}
And a class B that imports A和一个进口A的class B
import A from './a'
export default class B {
g() {
const a = new A()
return a.f()
}
gCallsStaticF() {
return A.staticF()
}
}
Now you want to mock up A. It is easy to mock up f():现在你想模拟 A。模拟 f() 很容易:
import A from '../src/a'
import B from '../src/b'
jest.mock('../src/a', () => {
return jest.fn().mockImplementation(() => {
return { f: () => { return 'mockedA.f()'} }
})
})
describe('Wallet', () => {
it('should work', () => {
const b = new B()
const result = b.g()
console.log(result) // prints 'mockedA.f()'
})
})
However, I could not find any documentation on how to mock up A.staticF.但是,我找不到任何关于如何模拟 A.staticF 的文档。 Is this possible?
这可能吗?
You can just assign the mock to the static method您可以将模拟分配给静态方法
import A from '../src/a'
import B from '../src/b'
jest.mock('../src/a')
describe('Wallet', () => {
it('should work', () => {
const mockStaticF = jest.fn().mockReturnValue('worked')
A.staticF = mockStaticF
const b = new B()
const result = b.gCallsStaticF()
expect(result).toEqual('worked')
})
})
Hope this will help you希望对你有帮助
// code to mock
export class AnalyticsUtil {
static trackEvent(name) {
console.log(name)
}
}
// mock
jest.mock('../src/AnalyticsUtil', () => ({
AnalyticsUtil: {
trackEvent: jest.fn()
}
}))
// code to mock
export default class Manager {
private static obj: Manager
static shared() {
if (Manager.obj == null) {
Manager.obj = new Manager()
}
return Manager.obj
}
nonStaticFunc() {
}
}
// mock
jest.mock('../src/Manager', () => ({
shared: jest.fn().mockReturnValue({
nonStaticFunc: jest.fn()
})
}))
// usage in code
someFunc() {
RNDefaultPreference.set('key', 'value')
}
// mock RNDefaultPreference
jest.mock('react-native-default-preference', () => ({
set: jest.fn()
}))
// code to mock
export namespace NavigationActions {
export function navigate(
options: NavigationNavigateActionPayload
): NavigationNavigateAction;
}
// mock
jest.mock('react-navigation', () => ({
NavigationActions: {
navigate: jest.fn()
}
}))
I managed to mock it in a separate file in the __mocks__
folder using prototyping.我设法使用原型在
__mocks__
文件夹中的一个单独文件中模拟它。 So you would do:所以你会这样做:
function A() {}
A.prototype.f = function() {
return 'a.f()';
};
A.staticF = function() {
return 'A.staticF()';
};
export default A;
We need to create a mock and give visibility for the mocked method to the test suite.我们需要创建一个模拟并将模拟方法的可见性提供给测试套件。 Below full solution with comments.
以下带有评论的完整解决方案。
let mockF; // here we make variable in the scope we have tests
jest.mock('path/to/StaticClass', () => {
mockF = jest.fn(() => Promise.resolve()); // here we assign it
return {staticMethodWeWantToMock: mockF}; // here we use it in our mocked class
});
// test
describe('Test description', () => {
it('here our class will work', () => {
ourTestedFunctionWhichUsesThisMethod();
expect(mockF).toHaveBeenCalled(); // here we should be ok
})
})
I went with the route of using jest.spyOn
.我选择了使用
jest.spyOn
的路线。
encryption.ts
export class Encryption {
static encrypt(str: string): string {
// ...
}
static decrypt(str: string): string {
// ...
}
}
property-encryption.spec.ts
import { Encryption } from './encryption'
import { PropertyEncryption } from './property-encryption'
describe('PropertyEncryption', () => {
beforeAll(() => {
jest
.spyOn(Encryption, 'encrypt')
.mockImplementation(() => 'SECRET')
jest
.spyOn(Encryption, 'decrypt')
.mockImplementation(() => 'No longer a secret')
})
it("encrypts object values and retains the keys", () => {
const encrypted = PropertyEncryption.encrypt({ hello: 'world' });
expect(encrypted).toEqual({ hello: 'SECRET' });
});
it("decrypts object values", () => {
const decrypted = PropertyEncryption.decrypt({ hello: "SECRET" });
expect(decrypted).toEqual({ hello: 'No longer a secret' });
});
})
Using Object.assign
on the mock constructor allows simultaneous mocking of the class and its static methods.在模拟构造函数上使用
Object.assign
允许同时模拟类及其静态方法。 Doing this allows you to achieve the same structure you get when creating a class with static members.这样做可以让您获得与创建具有静态成员的类时相同的结构。
import A from '../src/a'
import B from '../src/b'
jest.mock('../src/a', () =>
Object.assign(
jest.fn(
// constructor
() => ({
// mock instance here
f: jest.fn()
})),
{
// mock static here
staticF: jest.fn(),
}
)
)
Here's an example with an ES6 import.这是一个 ES6 导入的示例。
import { MyClass } from '../utils/my-class';
const myMethodSpy = jest.spyOn(MyClass, 'foo');
describe('Example', () => {
it('should work', () => {
MyClass.foo();
expect(myMethodSpy).toHaveBeenCalled();
});
});
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