Merge "Update readme" into main

## Adding a Test

By default tests should inherit from `RotationTestBase` or `NonRotationTestBase` and must override the variable `transitionToRun` (Kotlin) or the function `getTransitionToRun()` (Java).

Only tests that are not supported by these classes should inherit directly from the `FlickerTestBase` class.

By default, tests should inherit from `TestBase` and override the variable `transition` (Kotlin) or the function `getTransition()` (Java).

### Rotation animations and transitions

Inheriting from this class ensures the common assertions will be executed, namely:

Tests that rotate the device should inherit from `RotationTestBase`.

Tests that inherit from the class automatically receive start and end rotation values.  

Moreover, these tests inherit the following checks:

* all regions on the screen are covered

* status bar is always visible

* status bar rotates

* status bar is at the correct position at the start and end of the transition

* nav bar is always visible

* nav bar is rotates

* nav bar is at the correct position at the start and end of the transition

The default tests can be disabled by overriding the respective methods and including an `@Ignore` annotation.

### Non-Rotation animations and transitions

For more examples of how a test looks like check `ChangeAppRotationTest` within the `Rotation` subdirectory.

`NonRotationTestBase` was created to make it easier to write tests that do not involve rotation (e.g., `Pip`, `split screen` or `IME`).

Tests that inherit from the class are automatically executed twice: once in portrait and once in landscape mode and the assertions are checked independently.

Moreover, these tests inherit the following checks:

* all regions on the screen are covered

* status bar is always visible

* nav bar is always visible

The default tests can be disabled by overriding the respective methods and including an `@Ignore` annotation.

### Exceptional cases

Tests that rotate the device should inherit from `RotationTestBase`.

This class allows the test to be freely configured and does not provide any assertions.  

### Example

Start by defining common or error prone transitions using `TransitionRunner`.

```kotlin

@LargeTest

@RunWith(Parameterized::class)

@FixMethodOrder(MethodSorters.NAME_ASCENDING)

class MyTest(

    beginRotationName: String,

    beginRotation: Int

) : NonRotationTestBase(beginRotationName, beginRotation) {

    init {

        mTestApp = MyAppHelper(InstrumentationRegistry.getInstrumentation())

    }

    override val transitionToRun: TransitionRunner

        get() = TransitionRunner.newBuilder()

            .withTag("myTest")

            .recordAllRuns()

            .runBefore { device.pressHome() }

            .runBefore { device.waitForIdle() }

            .run { testApp.open() }

            .runAfter{ testApp.exit() }

            .repeat(2)

            .includeJankyRuns()

            .build()

    @Test

    fun myWMTest() {

        checkResults {

            WmTraceSubject.assertThat(it)

                    .showsAppWindow(MyTestApp)

                    .forAllEntries()

        }

    }

    @Test

    fun mySFTest() {

        checkResults {

            LayersTraceSubject.assertThat(it)

                    .showsLayer(MyTestApp)

                    .forAllEntries()

        }

    }

}

```