How do I put new List<int> {1} in an NUNIT TestCase?

I have the method:

public static int Add(List<int> numbers)
    {
        if (numbers == null || numbers.Count == 0)
            return 0;

        if (numbers.Count == 1)
            return numbers[0];


        throw new NotImplementedException();
    }

Here is my test against it, but it does not like new List<int> {1} in the TestCase:

    [TestCase(new List<int>{1}, 1)]
    public void Add_WithOneNumber_ReturnsNumber(List<int> numbers)
    {

        var result = CalculatorLibrary.CalculatorFunctions.Add(numbers);

        Assert.AreEqual(1, result);
    }

It gives me the error:

An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type

Do I have to do it like this:

    [Test]
    public void Add_WithOneNumber_ReturnsNumber()
    {

        var result = CalculatorLibrary.CalculatorFunctions.Add(new List<int>{7});


        Assert.AreEqual(7, result);

        var result2 = CalculatorLibrary.CalculatorFunctions.Add(new List<int> {3});

        Assert.AreEqual(4,result2);
    }

There is one option to use TestCaseSource attribute. Here I provide a non-assert test with two cases just to see how it works:

[TestFixture]
public class TestClass
{
    private static readonly object[] _sourceLists = 
    {
        new object[] {new List<int> {1}},   //case 1
        new object[] {new List<int> {1, 2}} //case 2
    };

    [TestCaseSource("_sourceLists")]
    public void Test(List<int> list)
    {
        foreach (var item in list)
            Console.WriteLine(item);
    }
}

Anyhow I have to mention it is not the most evident solution and I would prefer neatly organized fixtures ignoring the fact they are more verbose

More information: https://github.com/nunit/docs/wiki/TestCaseSource-Attribute

My solution is simpler, I just use params. I hope this works for you!

[TestCase(1, 1)]
[TestCase(10, 5, 1, 4)]
[TestCase(25, 3, 5, 5, 12)]
public void Linq_Add_ShouldSumAllTheNumbers(int expected, params int[] numbers)
{
    var result = CalculatorLibrary.CalculatorFunctions.Add(numbers);
    Assert.AreEqual(expected, result);
}

Improve code for @Yurii Hohan answer:

private  static readonly object[] _Data =
        {
            new object[] {new List<int> {0}, "test"},
            new object[] {new List<int> {0, 5}, "test this"},
        };

[Test, TestCaseSource(nameof(_Data))]

Hope this help.

I often use strings and parsing as it renders nicely in the testrunner. Sample:

[TestCase("1, 2")]
[TestCase("1, 2, 3")]
public void WithStrings(string listString)
{
    var list = listString.Split(',')
                         .Select(int.Parse)
                         .ToList();
    ...
}

Looks like this in Resharper's runner:

You can use this :

[TestCase(new []{1,2,3})]
public void Add_WithOneNumber_ReturnsNumber(int[] numbers)