It's time for testing.

Over in the project pane,

let's create a new test class by right-clicking on the test folder.

New > Java Class, and let's name it MainActivityTest.

And let's choose to add this and all other new files to gif.

Now let's create our first Android test to test the functionality of our edit text.

Let's create a new test method @Test public void and

let's name it editTextUpdatesTextView and

make sure it throws an exception.

Let's start this method by commenting and the three As of testing.

First, we arrange the objects under test, then we act on those objects and

finally we assert that we get the expected result.

Starting with the Arrange section,

let's first create a new string variable named given string.

And set it equal to test123.

Then we need to call set text on our edit text and pass in our new string,

but before we can do that, our edit text needs to exist and before our

edit text can exist, main activity needs to have already been created.

Sounds like we need an instance of our activity.

Let's create a new main activity field at the top of the class.

Main activity and we'll call it activity.

Then let's create a new @Before method to set up our main activity.

Let's name it setUp public void setUp and brackets.

Next, inside our setUp method let's initialize our field

to a new main activity object.

Activity = new MainActivity.

Then on the next line, let's call activity.onCreate and

pass a null for the saved instance state.

Saved instance state is always null the first time you start an app, so

passing a null is no problem.

Now that we've initialized our MainActivity object and

called onCreate, our edit text should exist and

we should be able to access it by using activity.edittext.

Getting back to the Arrange section of our test, let's update our edit text

by calling activity.editText.setText and

passing in givenString.

Nice.

Moving on to the act section, we need a way to trigger our editText.

Let's see how it's done in the activity, but instead of navigating to the activity,

let's right click on main activity test up here and select split vertically.

Then let's close the copy on the left side and

now we can easily see main activity and main activity test at the same time.

Looking over at main activity, if we want our text view to update,

it looks like we need to call on editor action and

pass in an action ID of editorInfo.IME_Action_Done.

And luckily, we can do that pretty easily.

Back in the act section of our test,

just type activity.editText.onEditorAction and

pass in editorInfo.IME_Action_Done.

And that takes care of the act section.

Now let's close MainActivity to give the whole screen back to our test.

Finally, we just need to assert that our text view was

updated with the correct text.

Let's start by creating a new string variable named actualString.

To store what's actually in our text view, and

let's set it equal to activity.textView.getText().toString();.

Then we just need to assert that our given string is equal to our actual string.

On the next line let's type assertEquals and the parentheses

and then use Alt+Enter to add the static import, and

let's scroll a bit to choose one of these from the org.Junit package

to stay consistent with our other imports.

Then we just need to include our expected value, given string

and then our actual value, actual string, add a semi colon and there we go.

In the next video, we'll run our test and see what happens.