Learn TypeScript 3 by Building Web Applications

Writing basic tests

Now that everything is configured, let's start writing our tests:

1. Go to the services folder.
2. Create a file called population-service.spec.ts.

We recommend putting tests next to the code that they're testing and using the .spec.ts filename suffix. This is a common practice that makes it very straightforward to find the tests. Alternatively, you can use the .test.ts filename suffix.

3. Add the following code as a starting point:

import {PopulationServiceImpl} from "./population-service"; 

describe('population service', () => { 
    let sut: PopulationServiceImpl; 

    beforeEach(() => { 
       sut = new PopulationServiceImpl('https/foo'); // valid URL 
    }); 

    // add tests here 
}); 

With the preceding code, we've defined a dedicated scope for ...