TypeError: Cannot read property 'toBeA' of undefined

Question

I am trying to test my code using expect in nodejs. I required expect in code and I wanted to use a feature of expect called toBeA(). But unfortunately I am receiving error and unable to solve it. So,I am posting it here.

 const utils = require('./utils'); const expect = require('expect'); it('should add two numbers', () => { var result = utils.add(33,17); expect(result).toBe(50).toBeA('number'); }); 

This is my utils.js file

 module.exports.add = (a,b) => { return a+b; }; 

When I run the code I receive this error

  TypeError: Cannot read property 'toBeA' of undefined 

Answer 1

You cannot chain tests. toBe doesn't return anything, hence the error. You want

expect(result).toBe(50);
expect(result).toBeA('number');

(although the first one implies the other so you might as well omit it)

Answer 2

这工作正常而不是toBeA（）

expect(typeof result).toBe('number');

Answer 3

The expect assertion library has changed ownership. It was handed over to the Jest team, who in their infinite wisdom, created a new API .

You can still install expect as before, "npm install expect --save-dev", which is currently at version 21.2.1. Most methods names will remain unchanged except for a few, including 'toExist(), toBeA()'.

Answer 4

when use npm i expect --save-dev command for install expect, automatically install last version of expect. in last version chain do not work.

for solve this problem you should use below command:

npm i expect@1.20.2

in this version you can use chain expect like toNotBe .