Adding some unit tests for string (#211)

***NO_CI***

Author: CoryCharlton

Tests/NFUnitTestSystemLib/UnitTestStringTests.cs

@@ -967,6 +967,81 @@ public static void EndsWithNoMatchNonOrdinal_StringComparison()
             Assert.IsFalse(s.EndsWith(value));
         }
 
+        [TestMethod]
+        public void IndexOf_should_return_first_index_of_value()
+        {
+            // TODO: Check docs to confirm constraints on "count". Currently ArgumentOutOfRangeException is thrown if start + count exceeds string.Length
+            var source = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
+
+            Assert.AreEqual(0, source.IndexOf('a'), "Case 1");
+            Assert.AreEqual(26, source.IndexOf('a', 1), "Case 2");
+            Assert.AreEqual(26, source.IndexOf('a', 1, source.Length - 1), "Case 3");
+            Assert.AreEqual(0, source.IndexOf("a"), "Case 4");
+            Assert.AreEqual(26, source.IndexOf("a", 1), "Case 5");
+            Assert.AreEqual(26, source.IndexOf("a", 1, source.Length - 1), "Case 6");
+        }
+
+        [TestMethod]
+        public void IndexOf_should_return_negative_one_if_source_is_empty_string()
+        {
+            Assert.AreEqual(-1, string.Empty.IndexOf('.'), "Case 1");
+            Assert.AreEqual(-1, string.Empty.IndexOf('.', 1), "Case 2");
+            Assert.AreEqual(-1, string.Empty.IndexOf('.', 1, 2), "Case 3");
+            Assert.AreEqual(-1, string.Empty.IndexOf("."), "Case 4");
+            Assert.AreEqual(-1, string.Empty.IndexOf(".", 1), "Case 5");
+            Assert.AreEqual(-1, string.Empty.IndexOf(".", 1, 2), "Case 6");
+        }
+
+        [TestMethod]
+        public void IndexOf_should_return_negative_one_if_value_is_not_found()
+        {
+            var source = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
+
+            Assert.AreEqual(-1, source.IndexOf('.'), "Case 1");
+            Assert.AreEqual(-1, source.IndexOf('.', 1), "Case 2");
+            Assert.AreEqual(-1, source.IndexOf('.', 1, 2), "Case 3");
+            Assert.AreEqual(-1, source.IndexOf("."), "Case 4");
+            Assert.AreEqual(-1, source.IndexOf(".", 1), "Case 5");
+            Assert.AreEqual(-1, source.IndexOf(".", 1, 2), "Case 6");
+        }
+
+        [TestMethod]
+        public void LastIndexOf_should_return_last_index_of_value()
+        {
+            var source = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
+
+            Assert.AreEqual(26, source.LastIndexOf('a'), "Case 1");
+            Assert.AreEqual(0, source.LastIndexOf('a', 1), "Case 2");
+            Assert.AreEqual(0, source.LastIndexOf('a', 1, 2), "Case 3");
+            Assert.AreEqual(26, source.LastIndexOf("a"), "Case 4");
+            Assert.AreEqual(0, source.LastIndexOf("a", 1), "Case 5");
+            Assert.AreEqual(0, source.LastIndexOf("a", 1, 2), "Case 6");
+        }
+
+        [TestMethod]
+        public void LastIndexOf_should_return_negative_one_if_source_is_empty_string()
+        {
+            Assert.AreEqual(-1, string.Empty.LastIndexOf('.'), "Case 1");
+            Assert.AreEqual(-1, string.Empty.LastIndexOf('.', 1), "Case 2");
+            Assert.AreEqual(-1, string.Empty.LastIndexOf('.', 1, 2), "Case 3");
+            Assert.AreEqual(-1, string.Empty.LastIndexOf("."), "Case 4");
+            Assert.AreEqual(-1, string.Empty.LastIndexOf(".", 1), "Case 5");
+            Assert.AreEqual(-1, string.Empty.LastIndexOf(".", 1, 2), "Case 6");
+        }
+
+        [TestMethod]
+        public void LastIndexOf_should_return_negative_one_if_value_is_not_found()
+        {
+            var source = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
+
+            Assert.AreEqual(-1, source.LastIndexOf('.'), "Case 1");
+            Assert.AreEqual(-1, source.LastIndexOf('.', 1), "Case 2");
+            Assert.AreEqual(-1, source.LastIndexOf('.', 1, 2), "Case 3");
+            Assert.AreEqual(-1, source.LastIndexOf("."), "Case 4");
+            Assert.AreEqual(-1, source.LastIndexOf(".", 1), "Case 5");
+            Assert.AreEqual(-1, source.LastIndexOf(".", 1, 2), "Case 6");
+        }
+
         /// <summary>
         /// A class whose ToString method return null
         /// </summary>