diff --git a/appveyor.yml b/appveyor.yml
index 855f34f..a6edfb8 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,7 +1,17 @@
-image: Visual Studio 2017
+image: Visual Studio 2019
+
+init:
+  - git config --global core.autocrlf true
+
+environment:
+  matrix:
+  - solution: Semester4/Workflows/Workflows.sln
 
 before_build:
-    - nuget restore semester2/6.1/HW6T2.sln
+  - nuget restore %solution%
 
 build:
-    project: semester2/2.3/2.3.sln
+  project: $(solution)
+
+test_script:
+  - dotnet test %solution%
diff --git a/semester4/Workflows/Workflows.Tests/Program.fs b/semester4/Workflows/Workflows.Tests/Program.fs
new file mode 100644
index 0000000..0695f84
--- /dev/null
+++ b/semester4/Workflows/Workflows.Tests/Program.fs
@@ -0,0 +1 @@
+module Program = let [<EntryPoint>] main _ = 0
diff --git a/semester4/Workflows/Workflows.Tests/RoundWorkflowTest.fs b/semester4/Workflows/Workflows.Tests/RoundWorkflowTest.fs
new file mode 100644
index 0000000..8b9400f
--- /dev/null
+++ b/semester4/Workflows/Workflows.Tests/RoundWorkflowTest.fs
@@ -0,0 +1,68 @@
+module Workflows.Tests
+
+open NUnit.Framework
+open FsUnit
+open RoundWorkflow
+
+
+
+[<Test>]
+let ``zero accuracy test`` () =
+    let workflow = RoundResultBuilder(0)
+    workflow {
+        let! a = 1.0 * 1.5
+        let! b = 1.5 * 5.0
+        let! c = b / a
+        return c
+    } |> should equal 4
+
+[<Test>]
+let ``one digit accuracy test `` () =
+    let workflow = RoundResultBuilder(1)
+    workflow {
+        let! a = 2.5 * 5.0
+        return a
+    } |> should equal 12.5
+
+[<Test>]
+let ``two digit accuracy test`` () =
+    let workflow = RoundResultBuilder(2)
+    workflow {
+        let! a = 1.5 * 1.5
+        let! b = 1.1 * 1.4
+        let! c = a / b
+        return c
+    } |> should equal 1.46
+
+[<Test>]
+let ``three digits accuracy test`` () =
+    let workflow = RoundResultBuilder(3)
+    workflow {
+        let! a = 1.5 * 1.5
+        let! b = 1.1 * 1.4
+        let! c = 1.25 * 2.54
+        let! d = 32.3421 / 7.1224
+        let! e = a + c * (b / d)
+        return e
+    } |> should (equalWithin 0.0001) 3.327
+
+[<Test>]
+let ``four digits accuracy test`` () =
+    let workflow = RoundResultBuilder(4)
+    workflow {
+        let! a = 1.111 * 1.5
+        let! b = 1.1 / 2.345
+        let! c = 1.25 + 2.54
+        let! d = 32.3421 / 7.1224
+        let! e = a * c - (b / d)
+        return e
+    } |> should (equalWithin 0.00001) 6.2127
+
+[<Test>]
+let ``example test`` () =
+    let workflow = RoundResultBuilder(3)
+    workflow {
+        let! a = 2.0 / 12.0
+        let! b = 3.5
+        return a / b
+    } |> should (equalWithin 0.0001) 0.048
\ No newline at end of file
diff --git a/semester4/Workflows/Workflows.Tests/StringWorkflowTests.fs b/semester4/Workflows/Workflows.Tests/StringWorkflowTests.fs
new file mode 100644
index 0000000..533041a
--- /dev/null
+++ b/semester4/Workflows/Workflows.Tests/StringWorkflowTests.fs
@@ -0,0 +1,72 @@
+module StringWorkflowTests
+
+open NUnit.Framework
+open FsUnit
+open StringWorkflow
+
+let workflow = StringBuilder()
+
+[<Test>]
+let ``simple plus test`` () =
+    workflow {
+        let! a = "5"
+        let! b = "2"
+        let c = a + b
+        return c
+    } |> should equal (Some(7))
+
+[<Test>]
+let ``simple multiply test`` ()=
+    workflow {
+        let! a = "3"
+        let! b = "15"
+        let c = b * a
+        return c
+    } |> should equal (Some(45))
+
+[<Test>]
+let ``simple test`` () =
+    workflow {
+        let! a = "3"
+        let! b = "15"
+        let! c = "2"
+        let d = c * b
+        let e = d / a
+        return e
+    } |> should equal (Some(10))
+
+[<Test>]
+let ``simple subtraction test`` () =
+    workflow {
+        let! a = "3"
+        let! b = "15"
+        let c = b - a
+        return c
+    } |> should equal (Some(12))
+
+[<Test>]
+let ``simple division test`` () =
+    workflow {
+        let! a = "3"
+        let! b = "15"
+        let c = b / a
+        return c
+    } |> should equal (Some(5))
+
+[<Test>]
+let ``one word test`` () =
+    workflow {
+        let! a = "3"
+        let! b = "isword"
+        let c = a + b
+        return c
+    } |> should equal None
+
+[<Test>]
+let ``two words test`` () =
+    workflow {
+        let! a = "mmhmhmh"
+        let! b = "isword"
+        let c = a / b
+        return c
+    } |> should equal None
\ No newline at end of file
diff --git a/semester4/Workflows/Workflows.Tests/Workflows.Tests.fsproj b/semester4/Workflows/Workflows.Tests/Workflows.Tests.fsproj
new file mode 100644
index 0000000..0b9059d
--- /dev/null
+++ b/semester4/Workflows/Workflows.Tests/Workflows.Tests.fsproj
@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+
+        <IsPackable>false</IsPackable>
+        <GenerateProgramFile>false</GenerateProgramFile>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="FsUnit" Version="4.0.1" />
+        <PackageReference Include="nunit" Version="3.12.0" />
+        <PackageReference Include="NUnit3TestAdapter" Version="3.15.1" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <Compile Include="RoundWorkflowTest.fs" />
+        <Compile Include="StringWorkflowTests.fs" />
+        <Compile Include="Program.fs" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\Workflows\Workflows.fsproj" />
+    </ItemGroup>
+
+</Project>
diff --git a/semester4/Workflows/Workflows.sln b/semester4/Workflows/Workflows.sln
new file mode 100644
index 0000000..d58b492
--- /dev/null
+++ b/semester4/Workflows/Workflows.sln
@@ -0,0 +1,22 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Workflows", "Workflows\Workflows.fsproj", "{5AF0A1D8-0BFE-4046-B410-F7D147EF368B}"
+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Workflows.Tests", "Workflows.Tests\Workflows.Tests.fsproj", "{D70FC128-7397-4ABC-9E14-69BFC7C044CA}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{5AF0A1D8-0BFE-4046-B410-F7D147EF368B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{5AF0A1D8-0BFE-4046-B410-F7D147EF368B}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{5AF0A1D8-0BFE-4046-B410-F7D147EF368B}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{5AF0A1D8-0BFE-4046-B410-F7D147EF368B}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D70FC128-7397-4ABC-9E14-69BFC7C044CA}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D70FC128-7397-4ABC-9E14-69BFC7C044CA}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D70FC128-7397-4ABC-9E14-69BFC7C044CA}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D70FC128-7397-4ABC-9E14-69BFC7C044CA}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal
diff --git a/semester4/Workflows/Workflows/RoundWorkflow.fs b/semester4/Workflows/Workflows/RoundWorkflow.fs
new file mode 100644
index 0000000..0d67b37
--- /dev/null
+++ b/semester4/Workflows/Workflows/RoundWorkflow.fs
@@ -0,0 +1,10 @@
+module RoundWorkflow
+
+open System
+
+/// Workflow witch calculates expression and rounding its result
+type RoundResultBuilder(accuracy : int) =
+    member this.Bind(x : float, f) =
+        Math.Round(x, accuracy) |> f
+    member this.Return(x : float) =
+        Math.Round(x, accuracy)
\ No newline at end of file
diff --git a/semester4/Workflows/Workflows/StringWorkflow.fs b/semester4/Workflows/Workflows/StringWorkflow.fs
new file mode 100644
index 0000000..387b259
--- /dev/null
+++ b/semester4/Workflows/Workflows/StringWorkflow.fs
@@ -0,0 +1,12 @@
+module StringWorkflow
+
+open System
+
+/// Workflow witch calculates expression with string numbers
+type StringBuilder() =
+    member this.Bind(x : string, f) =
+        match Int32.TryParse(x) with
+        | true, number -> number |> f
+        | _ -> None
+    member this.Return(x) =
+        Some(x)
\ No newline at end of file
diff --git a/semester4/Workflows/Workflows/Workflows.fsproj b/semester4/Workflows/Workflows/Workflows.fsproj
new file mode 100644
index 0000000..7c42bb2
--- /dev/null
+++ b/semester4/Workflows/Workflows/Workflows.fsproj
@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <Compile Include="RoundWorkflow.fs" />
+        <Compile Include="StringWorkflow.fs" />
+    </ItemGroup>
+
+</Project>