testing-angular-app: A TypeScript repository from valerisuleo

What is automated testing?

It's the practice of writing code to test our code and then run those test in automated way.

Imagine we have this function somewhere in our application. It's base calculating fn and based on some conditions return a different value. Now with manual testing we have to launch the app on the browser and it takes time...

function calculate(input) {
  if (x) {
    return...;
  } else if (y) {
    return...;
  }
}

With automated testing it takes few seconds to test the this fun with different input.

var result = calculate(x);
var result = calculate(y);

Automated testing help you to catch defects before realising your software.

Be pragmatic

Although automated test has lots of pros, it does not always fit any team or project. First the team needs discipline in order to write and maintain automated tests. If you don't work in a team like that, it may cost you more than the value you can get out of it, because you will spend lots of time trying to fix broken code test.

Another factor is time and budget of your project. Let's say you are a startup and you have 3 months to turn a project into a real working software. It's better writing test only for part of app that will take more time testing manually.

Type of Tests

In general we have 3 different types of tests:

Unit
Integration
End-to-end

Unit Test

Test a component in isolation, without external resources (e.g. file system, database, api endpoints).

In angular terms that means testing a components in isolation without its templates or any other resources.

So if our component is using a service to talk to an api endpoint or a router we give to him a Fake Service/router, we assume that the service is doing its job properly and we focus on the functionality of the component.

They are:

Easiest to write
Super fast
Don't give us much confidence about the functionality of our app.

Integration Test

Test a component with external resources (e.g. file system, database, api endpoints).

In angular terms that means testing a components along with its templates.

We can't look at this class as a plain typescript class we need to look at it as angular component and It need to be tested into an angular environment. So we need to instruct angular to compile this class along with its template.

Require more code than a simple Unit Test.

Again if our component is using a service to talk to an api endpoint we give to him a Fake Service, we assume that the service is doing its job properly and we focus on the functionality of the component.

What's the difference with Unit?

It involves 2 pieces together: component + template. In other words we are testing the integration of our component with its template

End-to-end

Test the entire app as a whole.

Now we can write few integration tests for our component and it might pass the test, however the app might not still works as we expect. Because we are still looking at the individual component and not at the app as a whole.