My app has an upload file functionality, which allows the user to choose a file (with a specific mime type) from the file picker and then the file will be shown in a list in the app. I want to test this with espresso, but so far, I faced many problems.

How I open the file explorer:

private fun openFileExplorer() {
        val chooseFileIntent = Intent(Intent.ACTION_GET_CONTENT).apply {
            addCategory(Intent.CATEGORY_OPENABLE)
            type = mimeTypes.joinToString("|")
            putExtra(Intent.EXTRA_MIME_TYPES, mimeTypes)
        }
        startIntentForResult.launch(
            Intent.createChooser(
                chooseFileIntent,
                getString(R.string.select_source)
            )
        )
    }

How I listen to the activity result:

private val startIntentForResult =
        registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result: ActivityResult ->
            if (result.resultCode == Activity.RESULT_OK) {
                val uri = result.data?.data
                uri?.let { returnUri ->
                    // I get here
                    requireActivity().contentResolver.query(returnUri, null, null, null, null)
                }?.use { cursor ->
                    // I cannot get here, since the file "doesn't exist" (name this THERE)
                    // I need this cursor for several reasons
                    createDocument(cursor, uri)
                }
            }
        }

My Espresso test:

Intents.init()
intending(
    expectingIntending
).respondWith(createImageGallerySetResultStub(resources))

onView(withId(R.id.my_button)).perform(click())

intended(expectingIntending)
Intents.release()

// is not displayed, since it doesn't have any items in it
onView(withId(R.id.my_list)).check(matches(isDisplayed()))

....

fun createImageGallerySetResultStub(resources: Resources): Instrumentation.ActivityResult {
    val file = savePickedImage(resources)
    val uri = Uri.fromFile(file)
    val resultData = Intent()
    resultData.setData(uri)
    // if I use MediaStore.Images.Media.EXTERNAL_CONTENT_URI as uri, I can get THERE, but the folder is empty, I cannot use it...
    return Instrumentation.ActivityResult(Activity.RESULT_OK, resultData)
}

fun savePickedImage(resources: Resources): File? {
    val bm = BitmapFactory.decodeResource(resources, R.drawable.logo)
    val dir = InstrumentationRegistry.getInstrumentation().targetContext.cacheDir
    val file = File(dir.path, MY_IMAGE_NAME)
    val outStream: FileOutputStream
    return try {
        outStream = FileOutputStream(file)
        bm.compress(Bitmap.CompressFormat.PNG, 100, outStream)
        outStream.flush()
        outStream.close()
         file
    } catch (e: FileNotFoundException) {
        e.printStackTrace()
        null
    } catch (e: IOException) {
        e.printStackTrace()
        null
    }
}

The file that I make with savePickedImage gets created, I checked in the Device explorer.
But somehow during testing, it is not found and I cannot get further with my tests.
Any ideas?