Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

KeePass2PCL.Test.Shared/Cryptography/HashingStreamExTests.cs

@@ -0,0 +1,77 @@
+using NUnit.Framework;
+using System;
+using System.IO;
+using System.Text;
+
+#if KeePassLib
+using KeePassLib.Cryptography;
+#else
+using KeePass2PCL.Cryptography;
+#endif
+
+namespace KeePass2PCL.Test.Shared.Cryptography
+{
+  [TestFixture ()]
+  public class HashingStreamExTests
+  {
+    const string data = "test";
+
+    // The expected hash includes the \n added by WriteLine
+    static readonly byte[] sha256HashOfData = {
+      0xf2, 0xca, 0x1b, 0xb6, 0xc7, 0xe9, 0x07, 0xd0,
+      0x6d, 0xaf, 0xe4, 0x68, 0x7e, 0x57, 0x9f, 0xce,
+      0x76, 0xb3, 0x7e, 0x4e, 0x93, 0xb7, 0x60, 0x50,
+      0x22, 0xda, 0x52, 0xe6, 0xcc, 0xc2, 0x6f, 0xd2
+    };
+
+    [Test ()]
+    public void TestRead ()
+    {
+      // if we use larger size, StreamReader will read past newline and cause bad hash
+      var bytes = new byte[data.Length + 1];
+      using (var ms = new MemoryStream (bytes)) {
+        using (var sw = new StreamWriter (ms)) {
+          // set NewLine to ensure we don't run into cross-platform issues on Windows
+          sw.NewLine = "\n";
+          sw.WriteLine (data);
+        }
+      }
+      using (var ms = new MemoryStream (bytes)) {
+        using (var hs = new HashingStreamEx (ms, false, null)) {
+          using (var sr = new StreamReader (hs)) {
+            var read = sr.ReadLine ();
+            Assert.That (read, Is.EqualTo (data));
+          }
+          // When the StreamReader is disposed, it calls Dispose on the
+          //HasingStreamEx, which computes the hash.
+          Assert.That (hs.Hash, Is.EqualTo (sha256HashOfData));
+        }
+      }
+    }
+
+    [Test ()]
+    public void TestWrite ()
+    {
+      var bytes = new byte[16];
+      using (var ms = new MemoryStream (bytes)) {
+        using (var hs = new HashingStreamEx (ms, true, null)) {
+          using (var sw = new StreamWriter (hs)) {
+            // set NewLine to ensure we don't run into cross-platform issues on Windows
+            sw.NewLine = "\n";
+            sw.WriteLine (data);
+          }
+          // When the StreamWriter is disposed, it calls Dispose on the
+          //HasingStreamEx, which computes the hash.
+          Assert.That (hs.Hash, Is.EqualTo (sha256HashOfData));
+        }
+      }
+      using (var ms = new MemoryStream (bytes)) {
+        using (var sr = new StreamReader (ms)) {
+          var read = sr.ReadLine ();
+          Assert.That (read, Is.EqualTo (data));
+        }
+      }
+    }
+  }
+}
+