Jest testing function that calls eval

Question

I have a Vue TS project created with vue-cli 3.0.

This is the function I will test:

public hopJavascript(url: string) {
    eval(url);
}

And this is my test function using Jest framework:

test('navigation using javascript', () => {
    const url = "someurl";
    hopJavascript(url);
    
    expect(eval).toBeCalled();
});

Now i get this message,test failed console logging which is telling me that I need a mocked version of eval.

How can i mock eval ?

Errorname · Accepted Answer · 2018-11-29 14:20:39Z

1

Update

It seems you can't always override eval based on your JS environment (browser or node). See the answer to "How override eval function in javascript?" for more information

Original answer

~~I think you can redefine eval in your test file:~~

global.eval = jest.fn()

edited Nov 29, 2018 at 14:20

answered Nov 29, 2018 at 14:01

Errorname

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3 Comments

Yusuf Tezel Over a year ago

Then it says [ts] Cannot find name 'global'. [2304], do you know how to get ts recognize this

Errorname Over a year ago

After some research, it looks like you cannot always override eval

Yusuf Tezel Over a year ago

Nice, but it is old, maybe something changed.

zilijonas · Accepted Answer · 2019-01-22 08:30:49Z

0

You need to track your function with spyOn().

This solution should work for you.

import MyClass from '../MyClass';

test('navigation using javascript', () => {
    const url = "someurl";
    const spy = jest.spyOn(MyClass, 'eval');

    MyClass.hopJavascript(url);

    expect(spy).toHaveBeenCalled();
});

answered Jan 22, 2019 at 8:30

zilijonas

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