Navigation is a core functionality of all mobile apps, and the tedious work lies in manually testing every possible navigation path from a single screen, which can be both time-consuming and error-prone. One of the most useful new features is type-safe navigation, introduced in Navigation Component 2.8.0 through the use of serializable objects. However, integrating this feature requires some migration steps, which we will cover in this guide. This migration process will also illustrate the benefits of having automated navigation tests in place. However, integrating this new feature may require small or significant changes, depending on the app’s current implementation.

In this article, we will:

1. Implement navigation using the “old way.”
2. Develop navigation tests.
3. Migrate to the “new way” with type-safe navigation.

Note: Even though type-safe navigation is available, the “old way” is still supported in newer library versions. For this guide, we will use Navigation Component 2.8.6 for both approaches.

Implementing the navigation

Dependencies

Ensure the following dependencies are added to your project. The navigation testing library is particularly important as it provides TestNavHostController for testing.

Defining Navigation Routes

Navigation routes are defined as string constants:

Setting Up the Navigation Graph

Each composable screen is associated with a route in the navigation graph. Additionally, callback functions are defined to handle navigation:

Old version navigation graph

Integrating with the Scaffold Menu

These routes are also used to populate the navigation menu in the Scaffold. In this example, the Adaptive Library automatically handles menu type and positioning. If you want more information, refer to this article.

Testing the navigation

Now, let’s write tests to verify that navigation works correctly from both the menu and screen callbacks.

Note: Within composeTestRule.setContent, string resources are used instead of test tags to identify UI nodes, such as buttons.

By running this test, we can confirm that navigation is working correctly!

Old version passed tests

Migrating to Type-Safe Navigation

As mentioned earlier, navigation will be upgraded to leverage type-safe features.

Step 1: Enable Serialization Plugin

Ensure the serialization plugin is included in build.gradle.kts (if not already available):

kotlin-serialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }

plugins {
    alias(libs.plugins.kotlin.serialization) apply false
    ...
}

Step 2: Apply Plugin in Module

Ensure the serialization plugin is applied in the application module and any other module where it is needed.

plugins {
    alias(libs.plugins.kotlin.serialization)
    ...
}

Step 3: Migrate Routes to Serializable Objects

Instead of using string constants, define routes as serializable objects:

Step 4: Update the Navigation Graph

Modify the navigation graph to use serializable objects:

Step 5: Update the Scaffold Menu

Ensure the menu items use the updated navigation approach:

Step 6: Update Navigation Assertions in Tests

Instead of currentDestination, use currentBackStackEntry:

// Change this
assertTrue { navController.currentDestination?.route == NavigationRoutes.BOOK_SEARCH }

// For this
assertTrue { navController.currentBackStackEntry?.destination?.hasRoute<BookSearch>() == true }

Step 7: Modify setCurrentDestination

setCurrentDestination in TestNavHostController does not support serializable objects, so navigation functions must be used instead:

// Change this
composeTestRule.runOnUiThread {
  navController.setCurrentDestination(NavigationRoutes.BOOK_SEARCH)
}

// For this
composeTestRule.runOnUiThread {
  navController.navigate(BookSearch)
}

Full Test Code

Here is the complete test code to verify navigation:

Final Verification

After applying these changes, re-run the tests to ensure that navigation still functions correctly.

Migrated version passed tests

Closing

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This article is previously published on proandroiddev.com.