如何监视动态调用的函数答案

【问题标题】：How to spy on dynamically called function如何监视动态调用的函数
【发布时间】：2019-09-11 08:13:19
【问题描述】：

我正在使用 Javascript、Mocha、Chai 和 SinonJs。我想要做的是监视由另一个方法“compareUsingOperator”动态调用的方法“equals”。下面的代码显示了我的类“StringComparator”，它有两个方法“equals”和“compareUsingOperator”。

export default class StringComparator {

    private compareFunctionList: {[key in "=" | "!=" | "<>" | "<" | "<=" | ">" | ">="]: Function};

    public constructor() {
        this.compareFunctionList = {
            "=" : this.equals,
            "!=" : this.notEquals,
            "<>" : this.notEquals,
            "<" : this.lessThan,
            "<=" : this.lessThanOrEquals,
            ">" : this.greaterThan,
            ">=" : this.greaterThanOrEquals,
        };
    }

    public equals(value1: string, value2: string): boolean {
        if (typeof value1 != "string" || typeof value2 != "string") {
            console.log(value1);
            console.log(value2);
            throw new TypeError("Invalid data type!");
        }

        return (value1 === value2);
    }

    public compareUsingOperator(operator: "=" | "!=" | "<>" | "<" | "<=" | ">" | ">=", value1: string, value2: string): boolean {
        if (typeof operator != "string" || typeof value1 != "string" || typeof value2 != "string") {
            throw new TypeError("Invalid data type!");
        }

        if (!Object.keys(this.compareFunctionList).includes(operator)) {
            throw new ReferenceError("Undefined operator!");
        }

        const fn: Function = this.compareFunctionList[operator];
        return fn.call(this, value1, value2);
    }

}

这是我的单元测试：

            describe("compareUsingOperator", () => {
                context("calls", () => {
                    comparator.validOperators.forEach((operator) => {
                        it("the proper function according to the given operator", () => {
                            sinon.spy(actual, "equals");

                            actual.compareUsingOperator("=", comparator.value1, comparator.value2);

                            assert.called(actual.equals);
                            actual.equals.restore();
                        });
                    });

                });
            });

在我的单元测试中，我对“equals”方法设置了一个间谍，如下所示：

sinon.spy(actual, "equals");

“actual”是“StringComparator”的一个实例。

在下一步我打电话给：

actual.compareUsingOperator("=", comparator.value1, comparator.value2);

在这个方法中执行以下代码：

const fn: Function = this.compareFunctionList[operator];
        return fn.call(this, value1, value2);

这是对“equals”方法的调用。这也是我的问题。我想知道是否调用了“等于”。我正在使用以下断言：

assert.called(actual.equals);

我从 chai/sinon 得到的答案是：

AssertError: expected equals to have been called at least once but was never called

预期的行为应该是绿色测试。

我的单元测试有什么问题？在 console.log 的帮助下，我可以证明已经调用了“equals”。

问候

弗洛里安

【问题讨论】：

标签： mocha.js chai sinon

【解决方案1】：

我自己找到了答案。我不得不更换：

   const fn: Function = this.compareFunctionList[operator];
   return fn.call(this, value1, value2);

与：

    const fn: string = this.compareFunctionList[operator];
    return this[fn](value1, value2);

还有这个：

private compareFunctionList: {[key in "=" | "!=" | "<>" | "<" | "<=" | ">" | ">="]: Function};

    public constructor() {
        this.compareFunctionList = {
            "=" : this.equals,
            "!=" : this.notEquals,
            "<>" : this.notEquals,
            "<" : this.lessThan,
            "<=" : this.lessThanOrEquals,
            ">" : this.greaterThan,
            ">=" : this.greaterThanOrEquals,
        };
    }

这样：

private compareFunctionList: {[key in "=" | "!=" | "<>" | "<" | "<=" | ">" | ">="]: string};

    public constructor() {
        this.compareFunctionList = {
            "=" : "equals",
            "!=" : "notEquals",
            "<>" : "notEquals",
            "<" : "lessThan"
            "<=" : "lessThanOrEquals",
            ">" : "greaterThan",
            ">=" : "greaterThanOrEquals",
        };
    }

现在这个类是可测试的。

坦克和问候

弗洛里安

【讨论】：