Added Tests. Added Contains method

FlexArray/FlexArrayString.cs

@@ -28,14 +28,32 @@ public class FlexArrayString
         _data = new string[size];
     }
 
-    public void Add(string input)
+    public void Add(string value)
     {
         if (Capacity == Count)
         {
             Grow();
         }
 
-        _data[Count++] = input;
+        _data[Count++] = value;
+    }
+    
+    public bool Contains(string value)
+    {
+        if (Count == 0)
+        {
+            return false;
+        }
+
+        for (var i = 0; i < Count; i++)
+        {
+            if (_data[i] == value)
+            {
+                return true;
+            }
+        }
+
+        return false;
     }
 
     private void Grow()