public void Test_n1_returns_2()
        {
            //first prime is 2

            PrimeNumberGenerator generator = new PrimeNumberGenerator();
            var answer = generator.GetNumbers(1);
            Assert.AreEqual(2, answer[0]);
        }
        public void Test_n0_returnsEmpty()
        {
            //generate zero numbers means empty list

            PrimeNumberGenerator generator = new PrimeNumberGenerator();
            var answer = generator.GetNumbers(0);
            Assert.AreEqual(0, answer.Length);
        }
        public void Test_n5_returns_correct()
        {
            //first primes are 2, 3, 5, 7, 11

            PrimeNumberGenerator generator = new PrimeNumberGenerator();
            var answer = generator.GetNumbers(5);
            Assert.AreEqual(5, answer.Length);
            Assert.AreEqual(2, answer[0]);
            Assert.AreEqual(3, answer[1]);
            Assert.AreEqual(5, answer[2]);
            Assert.AreEqual(7, answer[3]);
            Assert.AreEqual(11, answer[4]);
        }