Compose UI Control

compose-ui-test-server

A library that enables AI coding agents to control Compose Desktop applications at runtime via HTTP.

• Repository: https://github.com/forketyfork/compose-ui-test-server
• Maven Central: io.github.forketyfork:compose-ui-test-server
• Current version: 0.2.0

Checking If Already Installed

Before setting up, check if the project already has the library:

grep -r "compose-ui-test-server\|composeuittest" --include="*.gradle*" --include="*.kt" .

Look for:

• Dependency on io.github.forketyfork:compose-ui-test-server
• Imports from io.github.forketyfork.composeuittest

If found, skip to Starting the Application.

Installing in a Compose Desktop Project

Step 1: Add the dependency

Find the app's build.gradle.kts and locate the desktop source set dependencies. Add compose-ui-test-server and compose.uiTest:

kotlin {
    sourceSets {
        val desktopMain by getting {
            dependencies {
                // Existing dependencies...

                // Add these two:
                implementation("io.github.forketyfork:compose-ui-test-server:0.2.0")
                @OptIn(org.jetbrains.compose.ExperimentalComposeLibrary::class)
                implementation(compose.uiTest)
            }
        }
    }
}

For projects using version catalogs, add to gradle/libs.versions.toml:

[libraries]
compose-ui-test-server = { module = "io.github.forketyfork:compose-ui-test-server", version = "0.2.0" }

Then reference in build.gradle.kts:

implementation(libs.compose.ui.test.server)

Step 2: Update the main function

Find the application's main() function (usually in Main.kt or similar). Replace the standard Compose Desktop launcher with runApplication:

Before (typical Compose Desktop main):

import androidx.compose.ui.window.Window
import androidx.compose.ui.window.application

fun main() = application {
    Window(onCloseRequest = ::exitApplication, title = "My App") {
        App()
    }
}

After (with agent control support):

import io.github.forketyfork.composeuittest.WindowConfig
import io.github.forketyfork.composeuittest.runApplication

fun main() =
    runApplication(
        windowConfig = WindowConfig(
            title = "My App",
            minimumWidth = 1024,
            minimumHeight = 768,
        ),
    ) {
        App()
    }

The app now runs normally by default, but supports agent control when launched with COMPOSE_UI_TEST_SERVER_ENABLED=true.

Step 3: Add test tags to UI elements

For agents to interact with specific UI elements, add test tags:

import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.testTag

Button(
    onClick = { /* ... */ },
    modifier = Modifier.testTag("login_button")
) {
    Text("Login")
}

TextField(
    value = username,
    onValueChange = { username = it },
    modifier = Modifier.testTag("username_field")
)

Starting the Application

# Normal mode (no server)
./gradlew run

# Agent-controlled mode (server enabled)
COMPOSE_UI_TEST_SERVER_ENABLED=true ./gradlew run

# With custom port (default is 54345)
COMPOSE_UI_TEST_SERVER_ENABLED=true COMPOSE_UI_TEST_SERVER_PORT=8080 ./gradlew run

Verifying the Server

Always check health first:

curl http://localhost:54345/health
# Expected: "OK"

Available Endpoints

Endpoint	Description
GET /health	Health check
GET /onNodeWithTag/{tag}/performClick	Click element by test tag
GET /onNodeWithTag/{tag}/performTextInput?text=...	Enter text (URL-encode the text!)
GET /onNodeWithText/{text}/performClick	Click element by display text
GET /waitUntilExactlyOneExists/tag/{tag}?timeout=5000	Wait for element by tag
GET /waitUntilExactlyOneExists/text/{text}?exact=true&timeout=5000	Wait for element by text
GET /waitForIdle	Wait for UI to stabilize
GET /captureScreenshot?path=screenshot.png	Capture screenshot

Workflow Pattern

Follow this sequence for reliable interactions:

# 1. Verify server is running
curl http://localhost:54345/health

# 2. Wait for UI to be ready
curl http://localhost:54345/waitForIdle

# 3. Perform action
curl "http://localhost:54345/onNodeWithTag/username/performTextInput?text=myuser"

# 4. Wait for UI to settle
curl http://localhost:54345/waitForIdle

# 5. Perform next action
curl http://localhost:54345/onNodeWithTag/login_button/performClick

# 6. Wait for result
curl "http://localhost:54345/waitUntilExactlyOneExists/tag/dashboard?timeout=10000"

# 7. Capture screenshot to verify
curl "http://localhost:54345/captureScreenshot?path=result.png"

Finding Test Tags

Search the codebase for existing test tags:

grep -r "testTag\|Modifier.testTag" --include="*.kt" .

Also check:

• CLAUDE.md for documented test tags
• Test files in src/*Test/ directories

Important Notes

• Always URL-encode special characters in text: space→%20, @→%40, &→%26
• Use waitForIdle between operations for stability
• Check HTTP status codes: 200=success, 400=bad request, 500=error
• Use appropriate timeouts for waits (default 5000ms may be too short)
• Screenshots require absolute paths

Error Handling

If an endpoint returns an error:

1. Check the element exists (search for its test tag in code)
2. Ensure UI has finished loading (waitForIdle)
3. Verify the server is still running (/health)
4. Try with a longer timeout for wait operations