Nunit: TestCaseSource does not expect to generate all test cases?

Question

Hi everyone I have a problem with generate test cases for TestCaseSource. I wrote this code for tests:

using System;
using System.Collections.Generic;
using System.Linq;

using NUnit.Framework;

namespace HeapSort.Tests
{
    [TestFixture]
    public class Tests
    {
        [Test, TestCaseSource(typeof(TestsGenerator),"TestCases")]
        public void IsEqualCollections(int[] received, int[] expected)
        {
            CollectionAssert.AreEqual(received, expected);
        }
    }

    public class TestsGenerator
    {
        public static IEnumerable<TestCaseData> TestCases
        {
            get
            {
                for (var i = 0; i < 25; i++)
                {
                    int[] t1 = GenerateCollection(i), t2 = t1.ToArray();
                    HeapSort.Sort(t1);
                    Array.Sort(t2);

                    yield return new TestCaseData(t1, t2);
                }
            }
        }

        private static int[] GenerateCollection(int seed)
        {
            var rnd = new Random(seed+DateTime.Now.Millisecond);
            int size = rnd.Next(100, 10000); 
            int[] array = new int[size];
                for (var i = 0; i < size; i++)
                    array[i] = rnd.Next(-100, 100);
            return array;

//            return Enumerable
//                .Repeat(100, rnd.Next(100, 10000))
//                .Select(i => rnd.Next(-100, 100))
//                .ToArray();
        }
    }
}

Where is the problem? Rather than get 25 tests, I get from 1 to 8. And often at the starting point of testing it shows that the tests are 7/8 and in the end there is only one test case.

How can I solve this problem?

UPD1: What's interesting is when I run tests through the console I handle all 25 tests how do I achieve the same results through the GUI!?

P.S. sorry for my bad english.

Perhaps I should mention that I'm working under Ubuntu in Rider

Answer 1

DateTime.Now is normally not very accurate. Your loop is generating many identical tests because they are all starting from the same seed. Why are you using a seed rather than simply letting Random work on its own?

Different runners will handle identical test in different ways. If you indicate what runner you are using to execute your tests, I can edit this answer with more information. However, in general, you most certainly don't want to generate a bunch of tests with the same data. They don't do anything for you!