add integration test

Signed-off-by: Jens Mueller <tschenser@gmx.de>

src/androidTest/java/com/owncloud/android/providers/DocumentsStorageProviderIT.kt

@@ -6,6 +6,7 @@ import androidx.documentfile.provider.DocumentFile
 import com.owncloud.android.AbstractOnServerIT
 import com.owncloud.android.R
 import com.owncloud.android.datamodel.OCFile.ROOT_PATH
+import com.owncloud.android.lib.common.network.WebdavUtils
 import com.owncloud.android.providers.DocumentsProviderUtils.assertExistsOnServer
 import com.owncloud.android.providers.DocumentsProviderUtils.assertListFilesEquals
 import com.owncloud.android.providers.DocumentsProviderUtils.assertReadEquals
@@ -18,6 +19,9 @@ import com.owncloud.android.providers.DocumentsProviderUtils.listFilesBlocking
 import com.owncloud.android.providers.DocumentsStorageProvider.DOCUMENTID_SEPARATOR
 import kotlinx.coroutines.runBlocking
 import net.bytebuddy.utility.RandomString
+import org.apache.commons.httpclient.HttpStatus
+import org.apache.commons.httpclient.methods.ByteArrayRequestEntity
+import org.apache.commons.httpclient.methods.PutMethod
 import org.junit.After
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
@@ -172,4 +176,32 @@ class DocumentsStorageProviderIT : AbstractOnServerIT() {
         assertFalse(file1.exists())
         assertExistsOnServer(client, ocFile1.remotePath, false)
     }
+
+    @Test
+    fun testServerChangedFileContent() {
+        // create random file
+        val file1 = rootDir.createFile("text/plain", RandomString.make())!!
+        file1.assertRegularFile(size = 0L)
+
+        val content1 = "initial content".toByteArray();
+
+        // write content bytes to file
+        contentResolver.openOutputStream(file1.uri, "wt").use {
+            it!!.write(content1)
+        }
+
+        val remotePath = file1.getOCFile(storageManager)!!.remotePath;
+
+        val content2 = "new content".toByteArray();
+
+        // modify content on server side
+        val putMethod = PutMethod(client.webdavUri.toString() + WebdavUtils.encodePath(remotePath));
+        putMethod.setRequestEntity(ByteArrayRequestEntity(content2));
+        assertEquals(HttpStatus.SC_NO_CONTENT, client.executeMethod(putMethod));
+        client.exhaustResponse(putMethod.responseBodyAsStream);
+        putMethod.releaseConnection(); // let the connection available for other methods
+
+        // read back content bytes
+        assertReadEquals(content2, contentResolver.openInputStream(file1.uri))
+    }
 }