Mocking global methods with Jest in Vue applications

Question

Mocking global methods with Jest in Vue applications

Currently, I am facing an issue with my project where a method defined in the script tag of the index.html file is causing Jest to fail during execution.

index.html

<script>
var getCookie = function(cookieVal) { return cookieVal; }
</script>

In order to address this problem, I have attempted to define the 'getCookie' variable within Jest globals as follows:

package.json

"jest": {
  "globals": {
      "getCookie": "someString"
    }
}

Although this successfully defines getCookie, running tests results in the following error message:

Error in data(): "TypeError: getCookie is not a function"

While this error is expected, I am uncertain about how to define it as a function in the globals object.

What would be the best approach for mocking my getCookie function in Jest?

javascript vue.js jestjs

Answer 1

Answer №1

Although the documentation for Jest mentions that the `globals` object should not contain functions, my own experimentation showed that it is possible to define global functions using a function expression or an arrow function:

{
  jest: {
    globals: {
      getCookie() { return 'someCookie' },  // function expression
      getCookie: () => 'someCookie',        // arrow function
    }
  }
}

Alternatively, you can also set up a setupFiles array in your Jest configuration to assign the value to global.getCookie:

// package.json
{
  jest: {
    setupFiles: ['./jest.setup.js']
  }
}

// jest.setup.js
global.getCookie = () => 'someCookie'

Answer 2

Although the documentation for Jest mentions that the `globals` object should not contain functions, my own experimentation showed that it is possible to define global functions using a function expression or an arrow function:

{
  jest: {
    globals: {
      getCookie() { return 'someCookie' },  // function expression
      getCookie: () => 'someCookie',        // arrow function
    }
  }
}

Alternatively, you can also set up a setupFiles array in your Jest configuration to assign the value to global.getCookie:

// package.json
{
  jest: {
    setupFiles: ['./jest.setup.js']
  }
}

// jest.setup.js
global.getCookie = () => 'someCookie'

Mocking global methods with Jest in Vue applications

Answer №1

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