CODEWITHSUNDEEP
javascriptunit-testingjestjs
Anna F
Anna F

Reputation: 1683

Jest - mock variables inside class

I have a class with config variables 

import  config  from '@/libs/config';

export class Logger {

  constructor () {
    this.level = this.testMethod(config.LOGGER);
    this.target_name = this.testMethod(config.LOGGER_TARGETS);
   }

And for example I have a method, where I use config variables

  testMethod(config) {
    return config;
  }

Is it possible to mock up the config variables (like config.LOGGER or config.LOGGER_TARGETS) to test my testMethod? How could I access and set it?

Upvotes: 1

Views: 3526

Answers (1)

Oleksandr Kovpashko
Oleksandr Kovpashko

Reputation: 800

Actually, you can test testMethod right now. The approach varies based on what you want to test. If you want to test that this method is called during creating a new instance, just mock it and check if it was called with required arguments. If you want to test that loggerInstance.level and loggerInstance.target_name has correct values, just check them afterward.

If you want to test method's logic – call it with params and check returned value.

Also, you can implement dependency inversion and get Logger class to receive config variables via constructor params. Pass params from @/libs/config in code that use this class and pass test params in tests. It's much better from the perspective of scalability and architecture.

Upvotes: 1

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