Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

ModernKeePassLib.Test/Cryptography/Cipher/StandardAesEngineTests.cs

@@ -0,0 +1,65 @@
+using System;
+using System.IO;
+
+#if KeePassLib
+using KeePassLib.Cryptography.Cipher;
+#else
+using ModernKeePassLibPCL.Cryptography.Cipher;
+#endif
+
+using NUnit.Framework;
+
+namespace ModernKeePassLib.Test.Shared.Cryptography.Cipher
+{
+  [TestFixture ()]
+  public class StandardAesEngineTests
+  {
+    [Test ()]
+    public void TestEncryptStream ()
+    {
+      // Test vector (official ECB test vector #356)
+      var pbIV = new byte[16];
+      var pbTestKey = new byte[32];
+      var pbTestData = new byte[16];
+      var pbReferenceCT = new byte[16] {
+        0x75, 0xD1, 0x1B, 0x0E, 0x3A, 0x68, 0xC4, 0x22,
+        0x3D, 0x88, 0xDB, 0xF0, 0x17, 0x97, 0x7D, 0xD7
+      };
+
+      pbTestData[0] = 0x04;
+
+      var outStream = new MemoryStream (new byte[16]);
+      var aes = new StandardAesEngine ();
+      var inStream = aes.EncryptStream (outStream, pbTestKey, pbIV);
+      new BinaryWriter (inStream).Write (pbTestData);
+      Assert.That (outStream.Position, Is.EqualTo (16));
+      outStream.Position = 0;
+      var outBytes = new BinaryReader (outStream).ReadBytes (16);
+      Assert.That(outBytes, Is.EqualTo (pbReferenceCT));
+    }
+
+    [Test ()]
+    public void TestDecryptStream ()
+    {
+      // Test vector (official ECB test vector #356)
+      var pbIV = new byte[16];
+      var pbTestKey = new byte[32];
+      var pbTestData = new byte[16];
+      var pbReferenceCT = new byte[16] {
+        0x75, 0xD1, 0x1B, 0x0E, 0x3A, 0x68, 0xC4, 0x22,
+        0x3D, 0x88, 0xDB, 0xF0, 0x17, 0x97, 0x7D, 0xD7
+      };
+
+      pbTestData[0] = 0x04;
+
+      // Possible Mono Bug? This only works with size >= 48
+      var inStream = new MemoryStream (new byte[48]);
+      inStream.Write (pbReferenceCT, 0, pbReferenceCT.Length);
+      inStream.Position = 0;
+      var aes = new StandardAesEngine ();
+      var outStream = aes.DecryptStream (inStream, pbTestKey, pbIV);
+      var outBytes = new BinaryReader (outStream).ReadBytes (16);
+      Assert.That(outBytes, Is.EqualTo (pbTestData));
+    }
+  }
+}