Made Add function, Added Tests. Added comments to int Tests

FlexArray.Test/FlexArrayIntTests.cs

@@ -2,6 +2,7 @@
 
 public class FlexArrayIntTests
 {
+    // Constructor tests
     [Fact]
     public void Construction_NoSize()
     {
@@ -36,6 +37,7 @@ public class FlexArrayIntTests
         array.Capacity.Should().Be(0, "negative size provided => set to 0");
     }
     
+    // Add tests
     [Fact]
     public void AddItem_Single()
     {
@@ -81,6 +83,7 @@ public class FlexArrayIntTests
         array.Count.Should().Be(FlexArrayInt.DefaultStartSize + 2);
     }
     
+    // Contains tests
     [Fact]
     public void Contains_Success()
     {
@@ -127,6 +130,7 @@ public class FlexArrayIntTests
              .Should().BeFalse("not contained in list");
     }
     
+    // Indexer tests
     [Fact]
     public void Indexer_Simple()
     {
@@ -176,6 +180,7 @@ public class FlexArrayIntTests
         }
     }
     
+    // Remove tests
     [Fact]
     public void Remove_ByIndex_Simple()
     {

FlexArray.Test/FlexArrayStringTests.cs

@@ -2,6 +2,7 @@
 
 public class FlexArrayStringTests
 {
+    // Constructor tests
     [Fact]
     public void Construction_NoSize()
     {
@@ -35,4 +36,51 @@ public class FlexArrayStringTests
         array.Count.Should().Be(0);
         array.Capacity.Should().Be(0, "negative size provided => set to 0");
     }
+    
+    // Add tests
+    [Fact]
+    public void AddItem_Single()
+    {
+        var array = new FlexArrayString();
+
+        array.Add("Hello");
+
+        array.Count.Should().Be(1, "one item added");
+        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize, "capacity unchanged");
+    }
+    
+    [Fact]
+    public void AddItem_Multiple_NoGrowth()
+    {
+        var array = new FlexArrayString();
+
+        array.Add("Hello");
+        array.Add("World");
+        array.Add("!");
+
+        array.Count.Should().Be(3, "three items added");
+        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize, "no growth required yet");
+    }
+
+    [Fact]
+    public void AddItem_Multiple_Growth()
+    {
+        var array = new FlexArrayString();
+
+        void AddItems(int count) 
+        {
+            for (var i = 0; i < count; i++)
+            {
+                // random string
+                array.Add(Guid.NewGuid().ToString());
+            }
+        }
+
+        AddItems(FlexArrayString.DefaultStartSize);
+        array.Capacity.Should().Be(FlexArrayString.DefaultStartSize);
+
+        AddItems(2);
+        array.Capacity.Should().BeGreaterThan(FlexArrayString.DefaultStartSize, "capacity exceeded, had to grow"); 
+        array.Count.Should().Be(FlexArrayString.DefaultStartSize + 2);
+    }
 }

FlexArray/FlexArrayString.cs

@@ -27,4 +27,21 @@ public class FlexArrayString
         var size = Math.Max(0, initialSize ?? DefaultStartSize);
         _data = new string[size];
     }
+
+    public void Add(string input)
+    {
+        if (Capacity == Count)
+        {
+            Grow();
+        }
+
+        _data[Count++] = input;
+    }
+
+    private void Grow()
+    {
+        var newData = new string[Capacity * 2];
+        Array.Copy(_data, newData, Count);
+        _data = newData;
+    }
 }