diff --git a/CourseApp.Tests/CourseApp.Tests.csproj b/CourseApp.Tests/CourseApp.Tests.csproj
index 8fb7e4a..e253b4b 100644
--- a/CourseApp.Tests/CourseApp.Tests.csproj
+++ b/CourseApp.Tests/CourseApp.Tests.csproj
@@ -9,6 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
+    <PackageReference Include="Moq" Version="4.15.2" />
     <PackageReference Include="xunit" Version="2.4.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.0.2" PrivateAssets="all" />
diff --git a/CourseApp.Tests/DemoTest.cs b/CourseApp.Tests/DemoTest.cs
index fdc46f5..ec1bd63 100644
--- a/CourseApp.Tests/DemoTest.cs
+++ b/CourseApp.Tests/DemoTest.cs
@@ -1,14 +1,27 @@
 using System;
 using Xunit;
+using Moq;
 
 namespace CourseApp.Tests
 {
     public class DemoTest
     {
         [Fact]
-        public void Test1()
+        public void NullException()
         {
-            Assert.True(true);
+            Car car1 = new Car();
+            var result = Assert.Throws<ArgumentNullException>(() => car1.Sum(null)).Message;
+            Assert.Equal("Value cannot be null.\nParameter name: One or more values is null.", result);
+        }
+
+        [Fact]
+        public void TestFuntionRun()
+        {
+            var mockAnotherService = new Mock<TouchPad>();
+            mockAnotherService.Setup(e => e.Touch(It.IsAny<int>()));
+            var motherBoard1 = new MotherBoard(mockAnotherService.Object);
+            var result = motherBoard1.Touch();
+            mockAnotherService.Verify(e => e.Touch(It.IsAny<int>()), Times.Once());
         }
     }
 }
diff --git a/CourseApp/Car.cs b/CourseApp/Car.cs
new file mode 100644
index 0000000..bcb5197
--- /dev/null
+++ b/CourseApp/Car.cs
@@ -0,0 +1,20 @@
+using System;
+
+namespace CourseApp
+{
+    public class Car
+    {
+        private object firstSpeed = 12.9;
+
+        public double Sum(object secondSpeed)
+        {
+            if ((firstSpeed == null) || (secondSpeed == null))
+            {
+                throw new ArgumentNullException("One or more values is null.");
+            }
+
+            double sum = (double)firstSpeed + (double)secondSpeed;
+            return sum;
+        }
+    }
+}
\ No newline at end of file
diff --git a/CourseApp/MotherBoard.cs b/CourseApp/MotherBoard.cs
new file mode 100644
index 0000000..6f83dcd
--- /dev/null
+++ b/CourseApp/MotherBoard.cs
@@ -0,0 +1,20 @@
+using System;
+
+namespace CourseApp
+{
+    public class MotherBoard
+    {
+       private int times = 0;
+       private TouchPad touchPad1 = new TouchPad();
+
+       public MotherBoard(TouchPad touchPad2)
+       {
+           this.touchPad1 = touchPad2;
+       }
+
+       public int Touch()
+       {
+           return this.touchPad1.Touch(times);
+       }
+    }
+}
\ No newline at end of file
diff --git a/CourseApp/Program.cs b/CourseApp/Program.cs
index 248bbe4..0c16613 100644
--- a/CourseApp/Program.cs
+++ b/CourseApp/Program.cs
@@ -4,9 +4,24 @@ namespace CourseApp
 {
     public class Program
     {
-        public static void Main(string[] args)
+        public static void TaskN1()
         {
-            Console.WriteLine("Hello World!");
+            Car car1 = new Car();
+            object speed = 12.3;
+            Console.WriteLine(car1.Sum(speed));
+        }
+
+        public static void TaskN2()
+        {
+            TouchPad touchPad1 = new TouchPad();
+            MotherBoard motherBoard1 = new MotherBoard(touchPad1);
+            Console.WriteLine(motherBoard1.Touch());
+        }
+
+        public static void Main()
+        {
+            TaskN1();
+            TaskN2();
             Console.ReadLine();
         }
     }
diff --git a/CourseApp/TouchPad.cs b/CourseApp/TouchPad.cs
new file mode 100644
index 0000000..df0c568
--- /dev/null
+++ b/CourseApp/TouchPad.cs
@@ -0,0 +1,13 @@
+using System;
+
+namespace CourseApp
+{
+    public class TouchPad
+    {
+       public virtual int Touch(int times)
+       {
+            times++;
+            return times;
+       }
+    }
+}
\ No newline at end of file