How To Test Functions Returning Data From A Database

I have a function:

public List<Car> GetFourWheelDrives()
{
return dataContext.Cars.Where(c => c.IsFourWheelDrive == true).ToList();
}

Firstly it's kind of obvious what I'm trying to do here. Any suggestions on how I'm doing this? Any improvements?

So now I want to unit test this. Well is it a unit test? A unit test isn't suppose to touch the database right? So this is a functional test?

So say I write a test

[Test]
public void GetFourWheelDrives_NoParameters_ReturnAListOfOnlyCarsThatAreFourWheelDrives
{
Assert.Greater(dataContext.Cars.Where(c => c.IsFourWheelDrive == false).ToList().Count, 0);
var cars = GetFourWheelDrives();
Assert.Greater(cars.Count, 0);
Assert.AreEqual(cars.Count, cars.Where(c => c.IsFourWheelDrive == true).ToList().Count);
}

So first Assert I'm making sure cars that aren't 4WD exist in the database otherwise it wouldn't be a valid test.

Second Assert I'm making sure at least one was returned.

Third Assert I'm making sure that all the cars returned were in fact 4WD.

I know this isn't a good test because I'm using the same logic in the test as the function I'm testing. However this is the only way I can currently think of to do this.