Ello all，所以我一直在尝试编写期望某种异常类型的单元测试。我有一个引发该异常的函数，但是我仍然无法通过测试。为了进行故障排除，我已经尝试了抛出相同的异常而仍然失败。我可以通过比较消息来使其通过，但这似乎是一个可怕的主意。

我应该如何处理匹配的自定义异常的测试？

班级代码

export class EventEntity {

    comments : Array<string> = new Array<string>();

    constructor() {}

    public addComment(comment : string) {
        this.comments.push(comment);
    }

    public getCommentCount() : number {
        return this.comments.length;
    }

    public getCommentByOrder(commentNumber : number) : string {
        console.log(`getCommentByOrder with arg:${commentNumber}`);            

        let offset = 1;
        try {
            let result = this.comments[commentNumber - offset];
            return result;
        } catch (err){
                console.log(`getCommentByOrder:Error: ${err.toString()}`);
            console.log(`err: with arg:${commentNumber}`);
            if(err instanceof RangeError){
                throw new CommentNotFoundException();
            }
            throw err;
        }
    }
}

MyException

export class CommentNotFoundException extends Error {
    constructor(m?:string) 
    {
        let message : string  = m?m:"Comment number not found in event's comments.";        
        super(message);
        Object.setPrototypeOf(this, CommentNotFoundException.prototype);
    }
}

测试失败

@test shouldThrowIfCommentNumberIsGreaterThanTotalNumberOfComments() {
    let testEvent = new EventEntity();
    let expectedException = new CommentNotFoundException();
    //expect(testEvent.getCommentByOrder(5)).to.throw(expectedException);
    expect(()=> {
        throw new CommentNotFoundException();
    }).to.throw(new CommentNotFoundException());
}

更新

好的，我修改了。这按预期工作。没有以以下形式获取异常：

expect(testEvent.getCommentByOrder(5)).to.throw(CommentNotFoundException);

但是这样做：

expect(()=>{
        testEvent.getCommentByOrder(5);
}).to.throw(CommentNotFoundException);

这是带有更新代码的清单：

方法

public getCommentByOrder(commentNumber : number) : string {
    let offset = 1;
    let result = this.comments[commentNumber - offset];
    if (!result) {
        throw new CommentNotFoundException();
    } else {
        return result;
    }
}

测试

@test shouldThrowIfCommentNumberIsGreaterThanTotalNumberOfComments() {
    let testEvent = new EventEntity();
    expect(()=>{
            testEvent.getCommentByOrder(5);
    }).to.throw(CommentNotFoundException);
}

胜利，谢谢！