Added Index Tests

FlexArray.Test/FlexArrayStringTests.cs

@@ -130,4 +130,54 @@ public class FlexArrayStringTests
         array.Contains("!")
              .Should().BeFalse("not contained in list");
     }
+    
+    // Indexer tests
+    [Fact]
+    public void Indexer_Simple()
+    {
+        var array = new FlexArrayString();
+        array.Add("Goodbye World!");
+
+        array[0].Should().Be("Goodbye World!");
+    }
+
+    [Fact]
+    public void Indexer_Multiple()
+    {
+        var array = new FlexArrayString();
+        for (var i = 0; i < 100; i++)
+        {
+            array.Add((i+1).ToString());
+        }
+
+        array[20].Should().Be("21");
+        array[88].Should().Be("89");
+    }
+
+    [Theory]
+    [InlineData(-1, "negative index")]
+    [InlineData(2, "index too high")]
+    [InlineData(10, "index too high")]
+    public void Indexer_InvalidIndex(int index, string reason)
+    {
+        var array = new FlexArrayString();
+        array.Add("Hello");
+
+        array[index].Should().Be(String.Empty, reason);
+    }
+    
+    [Fact]
+    public void Iterate()
+    {
+        var array = new FlexArrayString();
+        for (var i = 0; i < 10; i++)
+        {
+            array.Add(i.ToString());
+        }
+
+        for (var i = 0; i < 10; i++)
+        {
+            array[i].Should().Be(i.ToString());
+        }
+    }
 }