Protect Signature creation from invalid parameters

Author: nulltoken

LibGit2Sharp.Tests/SignatureFixture.cs

@@ -28,5 +28,20 @@ public void CreatingASignatureWithAnEmailContainingZerosThrows(string email)
         {
             Assert.Throws<ArgumentException>(() => new Signature("Me", email, DateTimeOffset.Now));
         }
+
+        [Fact]
+        public void CreatingASignatureWithBadParamsThrows()
+        {
+            Assert.Throws<ArgumentNullException>(() => new Signature(null, "[email protected]", DateTimeOffset.Now));
+            Assert.Throws<ArgumentException>(() => new Signature(string.Empty, "[email protected]", DateTimeOffset.Now));
+            Assert.Throws<ArgumentNullException>(() => new Signature("Me", null, DateTimeOffset.Now));
+        }
+
+        [Fact]
+        public void CanCreateASignatureWithAnEmptyEmail()
+        {
+            var sig = new Signature("Me", string.Empty, DateTimeOffset.Now);
+            Assert.Equal(string.Empty, sig.Email);
+        }
     }
 }

LibGit2Sharp/Signature.cs

@@ -35,6 +35,8 @@ internal Signature(IntPtr signaturePtr)
         /// <param name="when">The when.</param>
         public Signature(string name, string email, DateTimeOffset when)
         {
+            Ensure.ArgumentNotNullOrEmptyString(name, "name");
+            Ensure.ArgumentNotNull(email, "email");
             Ensure.ArgumentDoesNotContainZeroByte(name, "name");
             Ensure.ArgumentDoesNotContainZeroByte(email, "email");