英文:
Jest mock testing with input
问题
// 为这个函数编写 jest 测试应该如何做？
const input = require('prompt-sync')();
export function choices(): void {
const choice = input("Choose a letter");
if (choice === "a") {
console.log("Airplane");
} if (choice === "b") {
console.log("Balloon");
} else {
console.log("Neither");
}
}
我知道我应该使用模拟 (mocking)。但是当输入存储在函数内而不是作为参数传递时，我不知道如何做。我不想改变这一点。
英文:
How can I write a jest test for this function?
const input = require('prompt-sync')();
export function choices(): void {
const choice = input("Choose a letter");
if (choice === "a") {
console.log("Airplane");
} if (choice === "b") {
console.log("Balloon");
} else {
console.log("Neither");
}
}
I know that I should use mocking. But I do not know how to do it when the input is being stored inside of the function, and not as a parameter. I do not want to change this.
答案1
得分: 0
你可以使用 jest.mock 来模拟你的 prompt-sync 模块。而且因为该模块返回一个返回你的 input 的函数，所以 Jest.mock 应该是这样的：
const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);
这应该在你的测试文件中的导入之前包含。
完整示例：
const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);
import { choices } from "../path/to/file";
describe("test", () => {
let consoleSpy: jest.SpyInstance;
beforeEach(() => {
consoleSpy = jest.spyOn(console, "log");
});
afterEach(() => {
jest.resetAllMocks();
});
it("should call the input", () => {
choices();
expect(mockInput).toHaveBeenCalledWith("Choose a letter");
});
it("should call A", () => {
mockInput.mockReturnValue("a");
choices();
expect(consoleSpy).toHaveBeenCalledWith("Airplane");
});
});
然而，我建议重构你的代码，以便更容易进行测试。
英文:
You can use jest.mock to mock your prompt-sync module. And since that module is returning a function that returns your input, Jest.mock would have something like:
const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);
Which should be included before the import in your test file.
Full example:
const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);
import { choices } from "../path/to/file";
describe("test", () => {
let consoleSpy: jest.SpyInstance;
beforeEach(() => {
consoleSpy = jest.spyOn(console, "log");
});
afterEach(() => {
jest.resetAllMocks();
});
it("should call the input", () => {
choices();
expect(mockInput).toHaveBeenCalledWith("Choose a letter");
});
it("should call A", () => {
mockInput.mockReturnValue("a");
choices();
expect(consoleSpy).toHaveBeenCalledWith("Airplane");
});
});
However I advice refactoring your code to make it easily testable
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