diff --git a/.travis.yml b/.travis.yml
index dd23f68d..64b5f022 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,6 +20,8 @@ before_cache:
   - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
   - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
 
+script: ./gradlew check
+
 cache:
   directories:
     - $HOME/.gradle/caches/
@@ -37,4 +39,4 @@ deploy:
   on:
     repo: stevesoltys/backup
     tags: true
-  skip_cleanup: true
\ No newline at end of file
+  skip_cleanup: true
diff --git a/app/build.gradle b/app/build.gradle
index cd662b64..88a2f425 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -12,6 +12,7 @@ android {
     defaultConfig {
         minSdkVersion 26
         targetSdkVersion 28
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {
@@ -108,4 +109,7 @@ dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.5.0'
     testImplementation 'io.mockk:mockk:1.9.3'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.5.0'
+
+    androidTestImplementation 'androidx.test:runner:1.2.0'
+    androidTestImplementation 'androidx.test:rules:1.2.0'
 }
diff --git a/app/src/androidTest/java/com/stevesoltys/backup/Test.kt b/app/src/androidTest/java/com/stevesoltys/backup/Test.kt
new file mode 100644
index 00000000..1dafbfea
--- /dev/null
+++ b/app/src/androidTest/java/com/stevesoltys/backup/Test.kt
@@ -0,0 +1,70 @@
+package com.stevesoltys.backup
+
+import androidx.documentfile.provider.DocumentFile
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.runner.AndroidJUnit4
+import com.stevesoltys.backup.settings.getBackupFolderUri
+import com.stevesoltys.backup.transport.backup.plugins.DocumentsStorage
+import com.stevesoltys.backup.transport.backup.plugins.createOrGetFile
+import org.junit.After
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.random.Random
+
+private const val filename = "test-file"
+
+@RunWith(AndroidJUnit4::class)
+class AndroidUnitTest {
+
+    private val context = InstrumentationRegistry.getInstrumentation().targetContext
+    private val folderUri = getBackupFolderUri(context)
+    private val deviceName = "device name"
+    private val storage = DocumentsStorage(context, folderUri, deviceName)
+
+    private lateinit var file: DocumentFile
+
+    @Before
+    fun setup() {
+        assertNotNull("Select a storage location in the app first!", storage.rootBackupDir)
+        file = storage.rootBackupDir?.createOrGetFile(filename)
+                ?: throw RuntimeException("Could not create test file")
+    }
+
+    @After
+    fun tearDown() {
+        file.delete()
+    }
+
+    @Test
+    fun testWritingAndReadingFile() {
+        // write to output stream
+        val outputStream = storage.getOutputStream(file)
+        val content = ByteArray(1337).apply { Random.nextBytes(this) }
+        outputStream.write(content)
+        outputStream.flush()
+        outputStream.close()
+
+        // read written data from input stream
+        val inputStream = storage.getInputStream(file)
+        val readContent = inputStream.readBytes()
+        inputStream.close()
+        assertArrayEquals(content, readContent)
+
+        // write smaller content to same file
+        val outputStream2 = storage.getOutputStream(file)
+        val content2 = ByteArray(42).apply { Random.nextBytes(this) }
+        outputStream2.write(content2)
+        outputStream2.flush()
+        outputStream2.close()
+
+        // read written data from input stream
+        val inputStream2 = storage.getInputStream(file)
+        val readContent2 = inputStream2.readBytes()
+        inputStream2.close()
+        assertArrayEquals(content2, readContent2)
+    }
+
+}
diff --git a/app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt b/app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt
index fe6ee589..e15466c1 100644
--- a/app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt
+++ b/app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt
@@ -21,7 +21,7 @@ class DocumentsProviderBackupPlugin(
     @Throws(IOException::class)
     override fun initializeDevice() {
         // get or create root backup dir
-        val rootDir = storage.rootBackupDir ?: throw IOException()
+        storage.rootBackupDir ?: throw IOException()
 
         // create backup folders
         val kvDir = storage.defaultKvBackupDir