Javascript 如何测试我的函数是否返回jest中另一个类的实例

我不太会开玩笑

我有一个这样的开关箱：

 export const findType = async (name) => {
    switch(name){
        case "apple":
            return new AppleClass()
        case "mango":
            return new MangoClass()
        default:
            return new VegetableClass()
    }
}

it('should return AppleClass', () => {
    expect(() => {
       let res =  findType("apple")
       console.log(res)
    }).toReturn(instanceof(AppleClass))
})

object instanceOf AppleClass

it('should return AppleClass', () => {
let obj = findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

it('should return AppleClass', async () => {
let obj = await findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

现在，我想编写jest测试用例来检查上面的开关用例。我的测试用例如下所示：

 export const findType = async (name) => {
    switch(name){
        case "apple":
            return new AppleClass()
        case "mango":
            return new MangoClass()
        default:
            return new VegetableClass()
    }
}

it('should return AppleClass', () => {
    expect(() => {
       let res =  findType("apple")
       console.log(res)
    }).toReturn(instanceof(AppleClass))
})

object instanceOf AppleClass

it('should return AppleClass', () => {
let obj = findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

it('should return AppleClass', async () => {
let obj = await findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

控制台日志（res）打印：

但我也犯了同样的错误

Expression expected.ts(1109)
Expected 0 arguments, but got 1.

在

---

如何测试这个。任何帮助都很好。

您必须以不同的方式设置传递给它的函数，因为instanceOf操作符需要检查一个对象，如下所示：

 export const findType = async (name) => {
    switch(name){
        case "apple":
            return new AppleClass()
        case "mango":
            return new MangoClass()
        default:
            return new VegetableClass()
    }
}

it('should return AppleClass', () => {
    expect(() => {
       let res =  findType("apple")
       console.log(res)
    }).toReturn(instanceof(AppleClass))
})

object instanceOf AppleClass

it('should return AppleClass', () => {
let obj = findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

it('should return AppleClass', async () => {
let obj = await findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

您应该尝试以下方法：

 export const findType = async (name) => {
    switch(name){
        case "apple":
            return new AppleClass()
        case "mango":
            return new MangoClass()
        default:
            return new VegetableClass()
    }
}

it('should return AppleClass', () => {
    expect(() => {
       let res =  findType("apple")
       console.log(res)
    }).toReturn(instanceof(AppleClass))
})

object instanceOf AppleClass

it('should return AppleClass', () => {
let obj = findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

it('should return AppleClass', async () => {
let obj = await findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

看到它工作

在函数返回承诺的情况下，测试应修改如下：

 export const findType = async (name) => {
    switch(name){
        case "apple":
            return new AppleClass()
        case "mango":
            return new MangoClass()
        default:
            return new VegetableClass()
    }
}

it('should return AppleClass', () => {
    expect(() => {
       let res =  findType("apple")
       console.log(res)
    }).toReturn(instanceof(AppleClass))
})

object instanceOf AppleClass

it('should return AppleClass', () => {
let obj = findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

it('should return AppleClass', async () => {
let obj = await findType("apple");
  let isApple = obj instanceof AppleClass;
  expect(isApple).toBe(true);
});

---

我已经编辑了上面链接中的代码，对于要返回承诺的函数，请检查它。

btw是一个运算符（不带大括号）。@NinaScholz，toReturn（instanceof AppleClass）也按预期给出了错误0个参数，但得到了1个。这是另一个错误。我不知道。谢谢，这是可行的，但是我的代码从类返回了一个承诺。我已经编辑了这个问题。请在问题描述中提供类定义。