diff --git a/BugPro/BugPro.csproj b/BugPro/BugPro.csproj
new file mode 100644
index 0000000..7fc7560
--- /dev/null
+++ b/BugPro/BugPro.csproj
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Stateless" Version="5.13.0" />
+  </ItemGroup>
+</Project>
diff --git a/BugPro/Program.cs b/BugPro/Program.cs
new file mode 100644
index 0000000..9a5cde6
--- /dev/null
+++ b/BugPro/Program.cs
@@ -0,0 +1,82 @@
+// Copyright 2026 NNTU-CS
+using Stateless;
+using System;
+
+namespace BugPro {
+  public class Bug {
+    public enum State {
+      Open, Assigned, InProgress, Resolved, Closed, Reopened
+    }
+
+    public enum Trigger {
+      Assign, Start, Resolve, Close, Reopen, Reset
+    }
+
+    private readonly StateMachine<State, Trigger> _machine;
+    private string _title;
+
+    public State CurrentState => _machine.State;
+
+    public Bug(string title) {
+      _title = title;
+      _machine = new StateMachine<State, Trigger>(State.Open);
+
+      _machine.Configure(State.Open)
+        .Permit(Trigger.Assign, State.Assigned);
+
+      _machine.Configure(State.Assigned)
+        .Permit(Trigger.Start, State.InProgress)
+        .Permit(Trigger.Reset, State.Open);
+
+      _machine.Configure(State.InProgress)
+        .Permit(Trigger.Resolve, State.Resolved)
+        .Permit(Trigger.Reset, State.Open);
+
+      _machine.Configure(State.Resolved)
+        .Permit(Trigger.Close, State.Closed)
+        .Permit(Trigger.Reopen, State.Reopened);
+
+      _machine.Configure(State.Closed)
+        .Permit(Trigger.Reopen, State.Reopened);
+
+      _machine.Configure(State.Reopened)
+        .Permit(Trigger.Assign, State.Assigned)
+        .Permit(Trigger.Resolve, State.Resolved);
+    }
+
+    public void Assign() => _machine.Fire(Trigger.Assign);
+    public void Start() => _machine.Fire(Trigger.Start);
+    public void Resolve() => _machine.Fire(Trigger.Resolve);
+    public void Close() => _machine.Fire(Trigger.Close);
+    public void Reopen() => _machine.Fire(Trigger.Reopen);
+    public void Reset() => _machine.Fire(Trigger.Reset);
+
+    public bool CanAssign() => _machine.CanFire(Trigger.Assign);
+    public bool CanStart() => _machine.CanFire(Trigger.Start);
+    public bool CanResolve() => _machine.CanFire(Trigger.Resolve);
+    public bool CanClose() => _machine.CanFire(Trigger.Close);
+    public bool CanReopen() => _machine.CanFire(Trigger.Reopen);
+  }
+
+  class Program {
+    static void Main(string[] args) {
+      var bug = new Bug("Sample Bug");
+      Console.WriteLine($"Initial state: {bug.CurrentState}");
+
+      bug.Assign();
+      Console.WriteLine($"After Assign: {bug.CurrentState}");
+
+      bug.Start();
+      Console.WriteLine($"After Start: {bug.CurrentState}");
+
+      bug.Resolve();
+      Console.WriteLine($"After Resolve: {bug.CurrentState}");
+
+      bug.Close();
+      Console.WriteLine($"After Close: {bug.CurrentState}");
+
+      bug.Reopen();
+      Console.WriteLine($"After Reopen: {bug.CurrentState}");
+    }
+  }
+}
diff --git a/BugTests/BugTests.csproj b/BugTests/BugTests.csproj
new file mode 100644
index 0000000..9ee27db
--- /dev/null
+++ b/BugTests/BugTests.csproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="3.1.1" />
+    <PackageReference Include="MSTest.TestFramework" Version="3.1.1" />
+    <PackageReference Include="Stateless" Version="5.13.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\BugPro\BugPro.csproj" />
+  </ItemGroup>
+</Project>
diff --git a/BugTests/UnitTest1.cs b/BugTests/UnitTest1.cs
new file mode 100644
index 0000000..7f641eb
--- /dev/null
+++ b/BugTests/UnitTest1.cs
@@ -0,0 +1,179 @@
+// Copyright 2026 NNTU-CS
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using BugPro;
+using Stateless;
+using System;
+
+namespace BugTests {
+  [TestClass]
+  public class UnitTest1 {
+    [TestMethod]
+    public void Bug_InitialState_IsOpen() {
+      var bug = new Bug("Test");
+      Assert.AreEqual(Bug.State.Open, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Assign_MovesToAssigned() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      Assert.AreEqual(Bug.State.Assigned, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Start_MovesToInProgress() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      Assert.AreEqual(Bug.State.InProgress, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Resolve_MovesToResolved() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Resolve();
+      Assert.AreEqual(Bug.State.Resolved, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Close_MovesToClosed() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Resolve();
+      bug.Close();
+      Assert.AreEqual(Bug.State.Closed, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Reopen_FromClosed_MovesToReopened() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Resolve();
+      bug.Close();
+      bug.Reopen();
+      Assert.AreEqual(Bug.State.Reopened, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Reopen_FromResolved_MovesToReopened() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Resolve();
+      bug.Reopen();
+      Assert.AreEqual(Bug.State.Reopened, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Reset_FromAssigned_MovesToOpen() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Reset();
+      Assert.AreEqual(Bug.State.Open, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_Reset_FromInProgress_MovesToOpen() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Reset();
+      Assert.AreEqual(Bug.State.Open, bug.CurrentState);
+    }
+
+    [TestMethod]
+    public void Bug_ReopenedCanAssign() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Resolve();
+      bug.Reopen();
+      Assert.IsTrue(bug.CanAssign());
+    }
+
+    [TestMethod]
+    public void Bug_CanAssign_WhenOpen() {
+      var bug = new Bug("Test");
+      Assert.IsTrue(bug.CanAssign());
+    }
+
+    [TestMethod]
+    public void Bug_CannotStart_WhenOpen() {
+      var bug = new Bug("Test");
+      Assert.IsFalse(bug.CanStart());
+    }
+
+    [TestMethod]
+    public void Bug_CannotClose_WhenOpen() {
+      var bug = new Bug("Test");
+      Assert.IsFalse(bug.CanClose());
+    }
+
+    [TestMethod]
+    public void Bug_CannotReopen_WhenOpen() {
+      var bug = new Bug("Test");
+      Assert.IsFalse(bug.CanReopen());
+    }
+
+    [TestMethod]
+    public void Bug_CannotResolve_WhenOpen() {
+      var bug = new Bug("Test");
+      Assert.IsFalse(bug.CanResolve());
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(InvalidOperationException))]
+    public void Bug_Start_WhenOpen_ThrowsException() {
+      var bug = new Bug("Test");
+      bug.Start();
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(InvalidOperationException))]
+    public void Bug_Resolve_WhenOpen_ThrowsException() {
+      var bug = new Bug("Test");
+      bug.Resolve();
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(InvalidOperationException))]
+    public void Bug_Close_WhenOpen_ThrowsException() {
+      var bug = new Bug("Test");
+      bug.Close();
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(InvalidOperationException))]
+    public void Bug_Reopen_WhenOpen_ThrowsException() {
+      var bug = new Bug("Test");
+      bug.Reopen();
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(InvalidOperationException))]
+    public void Bug_Assign_WhenInProgress_ThrowsException() {
+      var bug = new Bug("Test");
+      bug.Assign();
+      bug.Start();
+      bug.Assign();
+    }
+
+    [TestMethod]
+    public void Bug_FullCycle_WorksCorrectly() {
+      var bug = new Bug("Test");
+      Assert.AreEqual(Bug.State.Open, bug.CurrentState);
+      bug.Assign();
+      Assert.AreEqual(Bug.State.Assigned, bug.CurrentState);
+      bug.Start();
+      Assert.AreEqual(Bug.State.InProgress, bug.CurrentState);
+      bug.Resolve();
+      Assert.AreEqual(Bug.State.Resolved, bug.CurrentState);
+      bug.Close();
+      Assert.AreEqual(Bug.State.Closed, bug.CurrentState);
+    }
+  }
+}
diff --git a/ST-4.sln b/ST-4.sln
index 58ea566..06cf042 100644
--- a/ST-4.sln
+++ b/ST-4.sln
@@ -1,14 +1,22 @@
-
+
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 17
-VisualStudioVersion = 17.0.31903.59
-MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BugPro", "BugPro\BugPro.csproj", "{11111111-1111-1111-1111-111111111111}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BugTests", "BugTests\BugTests.csproj", "{22222222-2222-2222-2222-222222222222}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
 		Release|Any CPU = Release|Any CPU
 	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{11111111-1111-1111-1111-111111111111}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{11111111-1111-1111-1111-111111111111}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{11111111-1111-1111-1111-111111111111}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{11111111-1111-1111-1111-111111111111}.Release|Any CPU.Build.0 = Release|Any CPU
+		{22222222-2222-2222-2222-222222222222}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{22222222-2222-2222-2222-222222222222}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{22222222-2222-2222-2222-222222222222}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{22222222-2222-2222-2222-222222222222}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal