Automata.Tests.SpecialRegexTests.TestMatchTermination C# (CSharp) Method

        public void TestMatchTermination()
        {
            //exponetial time
            string[] s = new string[] {
                "_a_aa_aa_aa@",
                "_a_aa_aa__aa@",
                "_a_aa_aa___aa@",
                "_a_aa_aa____aa@",
                //"_a_aa_aa_____aa@",
                //"_a_aa_aa______aa@", //takes 1 min!!!
            };
            var regex = new Regex("^(_?a?_?a?_?)+$", RegexOptions.Compiled);
            int t = 0;
            for (int i = 0; i < s.Length; i++)
            {
                t = System.Environment.TickCount;
                bool res = regex.IsMatch(s[i]);
                t = System.Environment.TickCount - t;
                TestContext.WriteLine("{0}, {1}", s[i].Length, t);
                Assert.IsFalse(res);
            }
            Assert.IsTrue(t > 1000);
        }