Mock virtual methods and not mock overridden of this methods with Moq - unit-testing

Question

In the below code I want to mock DB operation of GetTitle(int id) in FooBase class. But I want to test validations part in overridden GetTitle(int id).
I want to test overridden method but mock the base method
How I can mock virtual method and testing the overridden of it?
public abstract class FooBase
{
public virtual string GetTitle(int id) { return "Title From DB" /*Select From DB*/; }
}
public class Foo : FooBase
{
public override string GetTitle(int id)
{
if (id < 0)
return "Invalid id";
/*Doing somethings like other validations and etc*/
return $"Valid ID ({base.GetTitle(id)})";
}
}
public class FooTests
{
[Fact]
public void GetTitle() // Fails
{
// Arrange
var expectedID = 1;
var expectedResult = "Test";
var fooMock = new Mock<Foo>();
fooMock.Setup(x => x.GetTitle(It.IsAny<int>())).Returns(expectedResult);
var foo = fooMock.Object;
// Act
var title = foo.GetTitle(expectedID);
// Assert
fooMock.Verify(x => x.GetTitle(It.Is<int>(c => expectedID == c)), Times.Once);
Assert.Equal($"Valid ID ({expectedResult})", title);
}
}

Answer 1

If you can separate your logic into a different method (what might be a better design too), than you can use Moq's CallBase property to make the test call the mocked method.
public abstract class FooBase
{
public virtual string GetTitle(int id) { return "Title From DB" /*Select From DB*/; }
}
public class Foo : FooBase
{
public virtual string GetValidatedTitle(int id)
{
if (id < 0)
return "Invalid id";
/*Doing somethings like other validations and etc*/
return $"Valid ID ({GetTitle(id)})";
}
}
public class FooTests
{
[Fact]
public void GetTitle() // Now Passes
{
// Arrange
var expectedID = 1;
var expectedResult = "Test";
var fooMock = new Mock<Foo>() { CallBase = true };
fooMock.Setup(x => x.GetTitle(It.IsAny<int>())).Returns(expectedResult);
var foo = fooMock.Object;
// Act
var title = foo.GetValidatedTitle(expectedID);
// Assert
fooMock.Verify(x => x.GetTitle(It.Is<int>(c => expectedID == c)), Times.Once);
Assert.Equal($"Valid ID ({expectedResult})", title);
}
}