All language subtitles for 382 Writing the first unit test.en

In this video we will start looking at how we can write unit tests for our application and when we work

with flutter projects.

There is a convention that all tests are stored inside a folder called Test which is located at the

root of our project and if we open this folder we can find a single file called.

We did that dot dart and this is an example we did test that is added when we create a new flatter project

and we will look at.

We did tests later on.

So for now we can go ahead and delete this file.

Next we want to create our first unit test.

And since we already have a complete up we need to choose what we want to test.

And I suggest that we start with something simple.

For example we could open the signing folder and in here we have these validators that that file.

And as we can see we have unknown empty string validator class that implements one method.

And what this does is return true if the input string is not empty.

So I think this class is a good candidate for our first test.

So we're going to select the test folder.

And here we can create a new Dart file called Mali datas on this core test.

They'll start.

And next we can start writing some code.

And the first thing that we want to do is to create that void Main method which is the entry point for

all the tests in this file.

And the other thing that we need to do is to import a file called flatter test like this.

And now that we have done this we can start writing our first test and we do this by calling a method

called test.

And this takes up description which is a string and also closure which represents the body of our test.

But what is it that we want to test.

Exactly.

Well we can open the non empty string validate or class.

And I think our good first test would be to verify that the IS valid method returns true when we pass

an on empty string.

So let's implement this back to our test file.

We cannot.

A description that says no an empty string and inside the body I'm going to order final validate all

equals an empty string pollinator like this.

And I need to remember to import this.

And then we want to write an expectation.

So I'm going to type in some code and then I'm going to explain it.

So here I can I expect and then validator dot is valid with test.

And then through like this.

Okay.

So how does this work.

Well by adding this code to expect we are writing an assertion that checks that the value returned by

the first argument matches the value that we pass to the second argument.

And this entire expression is something that we can almost read in plain English because we are expecting

that validator that is valid means test is true.

And now that we have written our first test we can execute it.

So let's do that in the next video.