Nice and simple DSL for Espresso Compose in Kotlin
- Readability
- Reusability
- Extensible DSL
- Interceptors
The one of the main concepts of Jetpack Compose is a presentation of UI according to UI tree (UI hierarchy) approach with a parent-children relationships support. It means that the related UI test library has to support a parent-children relationships for Nodes by default. It will be discovered below how Kakao Compose library supports mentioned parent-children relationships approach.
Create your entity ComposeScreen where you will add the views involved in the interactions of the tests:
class MainActivityScreen(semanticsProvider: SemanticsNodeInteractionsProvider) :
ComposeScreen<MainActivityScreen>(
semanticsProvider = semanticsProvider
)ComposeScreen can represent the whole user interface or a portion of UI.
If you are using Page Object pattern you can put the interactions of Kakao inside the Page Objects.
Described way of Screen definition is very similar with the way that Kakao library offers.
But, usually, Screen in Jetpack Compose is a UI element (Node) too. That's why there is an additional option to declare ComposeScreen:
class MainActivityScreen(semanticsProvider: SemanticsNodeInteractionsProvider) :
ComposeScreen<MainActivityScreen>(
semanticsProvider = semanticsProvider,
viewBuilderAction = { hasTestTag("MainScreen") }
)So, ComposeScreen is a BaseNode's inheritor in Kakao-Compose library. And, as you've seen above, there is a possibility to describe
ComposeScreen without mandatory viewBuilderAction in cases when Screen is an abstraction without clear connection with any Node.
ComposeScreen contains KNode, these are the Jetpack Compose nodes where you want to do the interactions:
class MainActivityScreen(semanticsProvider: SemanticsNodeInteractionsProvider) :
ComposeScreen<MainActivityScreen>(
semanticsProvider = semanticsProvider,
viewBuilderAction = { hasTestTag("MainScreen") }
) {
val myButton: KNode = child {
hasTestTag("myTestButton")
}
}myButton was declared as a child of MainActivityScreen.
It means that myButton will be calculated using matchers specified in a lambda explicitly and a parent matcher implicitly (MainActivityScreen).
Under the hood, the SemanticMatcher of myButton is equal to hasTestTag("myTestButton") + hasParent(MainActivityScreen.matcher).
Also, KNode can be declared as a child of another KNode:
class MainActivityScreen(semanticsProvider: SemanticsNodeInteractionsProvider) :
ComposeScreen<MainActivityScreen>(
semanticsProvider = semanticsProvider,
viewBuilderAction = { hasTestTag("MainScreen") }
) {
val myButton: KNode = child {
hasTestTag("myTestButton")
}
val myButton2: KNode = myButton.child {
hasTestTag("myTestButton2")
}
}myButton2 will be calculated with the following
SemanticMatcher = hasTestTag("myTestButton") + hasParent(myButton.matcher) + hasParent(MainActivityScreen.matcher).
But, we advise not to abuse inheritance and use only the following chain: "ComposeScreen" - "Element of ComposeScreen".
The last, KNode can be declared without child function using only explicit matchers:
class MainActivityScreen(semanticsProvider: SemanticsNodeInteractionsProvider) :
ComposeScreen<MainActivityScreen>(
semanticsProvider = semanticsProvider,
viewBuilderAction = { hasTestTag("MainScreen") }
) {
val myButton = KNode(this) {
hasTestTag("myTestButton")
}
}Every KNode contains many matches. Some examples of matchers provided by Kakao Compose:
hasTexthasTestTag- and more
Like in Espresso you can combine different matchers:
val myButton = KNode(this) {
hasTestTag("myTestButton")
hasText("Button 1")
}The syntax of the test with Kakao is very easy, once you have the ComposeScreen and the KNode defined, you only have to apply
the actions or assertions like in Espresso:
class ExampleInstrumentedTest {
@Rule
@JvmField
val composeTestRule = createAndroidComposeRule<MainActivity>()
@Test
fun simpleTest() {
onComposeScreen<MainActivityScreen>(composeTestRule) {
myButton {
assertIsDisplayed()
assertTextContains("Button 1")
}
onNode {
hasTestTag("doesNotExist")
}.invoke {
assertDoesNotExist()
}
}
}
}To test lazy lists such as LazyRow or LazyColumn you should add KLazyListNode into your ComposeScreen:
val list = KLazyListNode(
semanticsProvider = semanticsProvider,
viewBuilderAction = { hasTestTag("LazyList") },
itemTypeBuilder = {
itemType(::LazyListItemNode)
itemType(::LazyListHeaderNode)
},
positionMatcher = { position -> SemanticsMatcher.expectValue(LazyListItemPosition, position) }
)Inside itemTypeBuilder function you should register KLazyListItemNode types to differentiate elements in lazy list:
class LazyListItemNode(
semanticsNode: SemanticsNode,
semanticsProvider: SemanticsNodeInteractionsProvider,
) : KLazyListItemNode<LazyListItemNode>(semanticsNode, semanticsProvider)
class LazyListHeaderNode(
semanticsNode: SemanticsNode,
semanticsProvider: SemanticsNodeInteractionsProvider,
) : KLazyListItemNode<LazyListHeaderNode>(semanticsNode, semanticsProvider) {
val title: KNode = child {
hasTestTag("LazyListHeaderTitle")
}
}The element position might be changed during the scroll due to lazy list construction, that’s why we should provide positionMatcher to determine the element position correctly. It could be achieved in different ways, for example you can determine item position through TestTag:
LazyColumn(
Modifier
.fillMaxSize()
.testTag("LazyList")
) {
itemsIndexed(items) { index, item ->
when (item) {
is LazyListItem.Header -> ListItemHeader(item, Modifier.testTag("position=$index"))
is LazyListItem.Item -> ListItemCell(item, Modifier.testTag("position=$index"))
}
}
}And then check this position inside positionMatcher lambda:
positionMatcher = { position -> hasTestTag("position=$position") }But it will be more convenient and less error prone to create custom semantics property and custom modifier:
val LazyListItemPosition = SemanticsPropertyKey<Int>("LazyListItemPosition")
var SemanticsPropertyReceiver.lazyListItemPosition by LazyListItemPosition
fun Modifier.lazyListItemPosition(position: Int): Modifier {
return semantics { lazyListItemPosition = position }
}And check an item position with SemanticsMatcher:
positionMatcher = { position -> SemanticsMatcher.expectValue(LazyListItemPosition, position) }So the typical lazy list test may look like this:
@Test
fun lazyListTest() {
onComposeScreen<LazyListScreen>(composeTestRule) {
list {
firstChild<LazyListHeaderNode> {
title.assertTextEquals("Items from 1 to 10")
}
childWith<LazyListItemNode> {
hasText("Item 1")
} perform {
assertTextEquals("Item 1")
}
childAt<LazyListItemNode>(10) {
assertTextEquals("Item 10")
}
}
}
}Check the lazy list test example for more information.
If you need to add custom logic during the Kakao-Compose -> Espresso(Compose) call chain (for example, logging) or
if you need to completely change the events/commands that are being sent to Espresso
during runtime in some cases, you can use the intercepting mechanism.
Interceptors are lambdas that you pass to a configuration DSL that will be invoked before calls happening from inside Kakao-Compose.
You have the ability to provide interceptors at two main different levels: Kakao-Compose runtime and any individual BaseNode instance.
Interceptors in Kakao-Compose support a parent-children concept too.
It means that any BaseNode inherits interceptors of his parents.
On each invocation of Espresso function that can be intercepted, Kakao-Compose will aggregate all available interceptors
for this particular call and invoke them in descending order: Active BaseNode interceptor -> Interceptor of the parent Active BaseNode -> ... -> Kakao-Compose interceptor.
Each of the interceptors in the chain can break the chain call by setting isOverride to true during configuration.
In that case Kakao-Compose will not only stop invoking remaining interceptors in the chain, but will not perform the Espresso
call. It means that in such case, the responsibility to actually invoke Espresso lies on the shoulders
of the developer.
Here's the examples of intercepting configurations:
class SomeTest {
@Before
fun setup() {
KakaoCompose { // KakaoCompose runtime
intercept {
onComposeInteraction {
onAll { list.add("ALL") }
onCheck { _, _ -> list.add("CHECK") }
onPerform { _, _ -> list.add("PERFORM") }
}
}
}
}
@Test
fun test() {
onComposeScreen<MyScreen> {
intercept {
onCheck { interaction, assertion -> // Intercept check() call
Log.d("KAKAO", "$interaction is checking $assertion")
}
}
myView {
intercept { // Intercepting ComposeInteraction calls on this individual Node
onPerform(true) { interaction, action -> // Intercept perform() call and overriding the chain
// When performing actions on this view, Kakao level interceptor will not be called
// and we have to manually call Espresso now.
Log.d("KAKAO_NODE", "$interaction is performing $action")
interaction.perform(action)
}
}
}
}
}
}For more detailed info please refer to the documentation.
By default Espresso using useUnmergedTree = true and it create a lot of inconveniences with node matching.
However you can override global parameter with KakaoComposeTestRule.
Every Compose screen require composeTestRule whats creating a lot of boilerplate like onComposeScreen<LazyListScreen>**(composeTestRule)** {
But you can provide composeTestRule into KakaoComposeTestRule and use all screens without injection like onComposeScreen<LazyListScreen> {, it possible to mix both
of implementation, injected composeTestRule will override provided via KakaoComposeTestRule.
You can find examples of it in Simple project
Maven
<dependency>
<groupId>io.github.kakaocup</groupId>
<artifactId>compose</artifactId>
<version><latest version></version>
<type>pom</type>
</dependency>or Gradle:
dependencies {
androidTestImplementation 'io.github.kakaocup:compose:<latest version>'
}dependencies {
androidTestImplementation("io.github.kakaocup:compose:<latest version>")
}Kakao Compose is an open source project, and depends on its users to improve it. We are more than happy to find you interested in taking the project forward.
Kindly refer to the Contribution Guidelines for detailed information.
Please refer to Code of Conduct document.
Kakao Compose is open source and available under the Apache License, Version 2.0.
