fixed unit test

main/crypto-aes/src/test/java/org/cryptomator/crypto/aes256/Aes256CryptorTest.java

@@ -80,7 +80,7 @@ public class Aes256CryptorTest {
 		final Aes256Cryptor cryptor = new Aes256Cryptor();
 
 		// encrypt:
-		final ByteBuffer encryptedData = ByteBuffer.allocate(256);
+		final ByteBuffer encryptedData = ByteBuffer.allocate(96 + plaintextData.length + 4096);
 		final SeekableByteChannel encryptedOut = new ByteBufferBackedSeekableChannel(encryptedData);
 		cryptor.encryptFile(plaintextIn, encryptedOut);
 		IOUtils.closeQuietly(plaintextIn);
@@ -112,7 +112,7 @@ public class Aes256CryptorTest {
 		final Aes256Cryptor cryptor = new Aes256Cryptor();
 
 		// encrypt:
-		final ByteBuffer encryptedData = ByteBuffer.allocate(256);
+		final ByteBuffer encryptedData = ByteBuffer.allocate(96 + plaintextData.length + 4096);
 		final SeekableByteChannel encryptedOut = new ByteBufferBackedSeekableChannel(encryptedData);
 		cryptor.encryptFile(plaintextIn, encryptedOut);
 		IOUtils.closeQuietly(plaintextIn);