Add unit test for null and exception handling.

src/AutoLazy.Tests/GenericTypeTests.cs

@@ -11,11 +11,16 @@ public class GenericTypeTests
         public void MockGeneric_with_int_should_be_lazy()
         {
             var target = new MockGeneric<int>(() => 123);
+
             Assert.AreEqual(0, target.GetValueCount);
+
             var first = target.GetValue();
+
             Assert.AreEqual(123, first);
             Assert.AreEqual(1, target.GetValueCount);
+
             var second = target.GetValue();
+
             Assert.AreEqual(first, second);
             Assert.AreEqual(1, target.GetValueCount);
         }
@@ -24,13 +29,81 @@ public void MockGeneric_with_int_should_be_lazy()
         public void MockGeneric_with_string_should_be_lazy()
         {
             var target = new MockGeneric<string>(() => Guid.NewGuid().ToString("n"));
+
             Assert.AreEqual(0, target.GetValueCount);
+
             var first = target.GetValue();
+
             Assert.AreNotEqual(null, first);
             Assert.AreEqual(1, target.GetValueCount);
+
             var second = target.GetValue();
+
             Assert.AreEqual(first, second);
             Assert.AreEqual(1, target.GetValueCount);
         }
+
+        [Test]
+        public void MockGeneric_with_null_string_should_be_lazy()
+        {
+            var target = new MockGeneric<string>(() => null);
+
+            Assert.AreEqual(0, target.GetValueCount);
+
+            var first = target.GetValue();
+
+            Assert.AreEqual(1, target.GetValueCount);
+
+            var second = target.GetValue();
+
+            Assert.AreEqual(first, second);
+            Assert.AreEqual(1, target.GetValueCount);
+        }
+
+        [Test]
+        public void MockGeneric_with_exception_string_should_be_lazy()
+        {
+            var target = new MockGeneric<object>(() => throw new ExpectedException());
+
+            Assert.AreEqual(0, target.GetValueCount);
+
+            object first = null;
+            ExpectedException firstException = null;
+            try
+            {
+                first = target.GetValue();
+            }
+            catch (ExpectedException e )
+            {
+                firstException = e;
+            }
+
+            Assert.IsNotNull(firstException);
+            Assert.AreEqual(1, target.GetValueCount);
+
+            object second = null;
+            ExpectedException secondException = null;
+            try
+            {
+                second = target.GetValue();
+            }
+            catch (ExpectedException e)
+            {
+                secondException = e;
+            }
+
+            Assert.IsNotNull(secondException);
+            Assert.AreSame(firstException, secondException );
+            Assert.AreEqual(1, target.GetValueCount);
+            Assert.AreEqual(first, second);
+
+        }
+
     }
+
+    public class ExpectedException:Exception
+    {
+
+    }
+
 }