---
title: "IdlingResource"
description: "Represents a resource of an application under test which can cause asynchronous background work
to happen during test execution (e.g. an http request in response to a button click).

By default, all interactions from the test with the compose tree (finding nodes, performing
gestures, making assertions) will be synchronized with pending work in Compose's internals (such
as applying state changes, recomposing, measuring, etc). This ensures that the UI is in a stable
state when the interactions are performed, so that e.g. no pending recompositions are still
scheduled that could potentially change the UI. However, any asynchronous work that is not done
through one of Compose's mechanisms won't be included in the default synchronization. For such
work, test authors can create an [IdlingResource] and register it into the test with
[registerIdlingResource][androidx.compose.ui.test.junit4.ComposeTestRule
.registerIdlingResource], and the interaction will wait for that resource to become idle prior to
performing it."
type: "interface"
---

<div class='type'>Interface</div>


<a id='references'></a>

<div class='sourceset sourceset-jvmAndAndroid'>JvmAndAndroid</div>



```kotlin
@JvmDefaultWithCompatibility
interface IdlingResource
```


Represents a resource of an application under test which can cause asynchronous background work
to happen during test execution (e.g. an http request in response to a button click).

By default, all interactions from the test with the compose tree (finding nodes, performing
gestures, making assertions) will be synchronized with pending work in Compose's internals (such
as applying state changes, recomposing, measuring, etc). This ensures that the UI is in a stable
state when the interactions are performed, so that e.g. no pending recompositions are still
scheduled that could potentially change the UI. However, any asynchronous work that is not done
through one of Compose's mechanisms won't be included in the default synchronization. For such
work, test authors can create an `IdlingResource` and register it into the test with
`registerIdlingResource`, and the interaction will wait for that resource to become idle prior to
performing it.


## Properties

<div class='sourceset sourceset-jvmAndAndroid'>JvmAndAndroid</div>


```kotlin
val isIdleNow: Boolean
```


Whether or not the `IdlingResource` is idle when reading this value. This should always be
called from the main thread, which is why it should be lightweight and fast.

If one idling resource returns `false`, the synchronization system will keep polling all
idling resources until they are all idle.



## Functions

```kotlin
fun getDiagnosticMessageIfBusy(): String?
```


Returns diagnostics that explain why the idling resource is busy, or `null` if the resource
is not busy. Default implementation returns `null`.