Add test from #343 to regression test suite

which demonstrates that Moq no longer cares about the precise return
type of methods if they otherwise match. This enables some scenarios
involving generic methods that previously weren't supported.

(It seems correct that Moq no longer tries to match method's return
types exactly. While technically not incorrect, it is unusual behavior
for most people coming from VB.NET or C#, where the return type is not
considered part of the method signature WRT method resolution.)

tests/Moq.Tests/Regressions/IssueReportsFixture.cs

@@ -1538,7 +1538,38 @@ protected Foo(SerializationInfo info, StreamingContext context) { }
 			}
 		}
 
-#endregion
+		#endregion
+
+		#region 343
+
+		public class Issue343
+		{
+			public class Fruit { }
+			public class Apple : Fruit { }
+			public class GreenApple : Apple { }
+			public class Orange : Fruit { }
+
+			public interface IFruitPicker
+			{
+				TFruit Pick<TFruit>() where TFruit : Fruit;
+			}
+
+			[Fact]
+			public void Return_type_variance_of_generic_method_setup()
+			{
+				var fruitPicker = new Mock<IFruitPicker>();
+				fruitPicker.Setup(m => m.Pick<Fruit>()).Returns(new Fruit());
+				fruitPicker.Setup(m => m.Pick<Apple>()).Returns(new GreenApple()); // set up method `Apple Pick<Apple>()`
+				fruitPicker.Setup(m => m.Pick<Orange>()).Returns(new Orange());
+
+				Assert.IsType<Fruit>(fruitPicker.Object.Pick<Fruit>());
+				Assert.IsType<GreenApple>(fruitPicker.Object.Pick<Apple>());
+				Assert.IsType<GreenApple>(fruitPicker.Object.Pick<GreenApple>()); // call method `GreenApple Pick<GreenApple>()` -- will the setup be matched despite the type difference?
+				Assert.IsType<Orange>(fruitPicker.Object.Pick<Orange>());
+			}
+		}
+
+		#endregion
 
 		#region 383