diff --git a/MergePDF.sln b/MergePDF.sln
index 7060b96..3b7fec8 100644
--- a/MergePDF.sln
+++ b/MergePDF.sln
@@ -5,6 +5,8 @@ VisualStudioVersion = 15.0.27130.2026
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MergePDF", "MergePDF\MergePDF.csproj", "{8BF6B775-F54A-4590-959B-FD6D5AEC1280}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MergePDFTests", "MergePDFTests\MergePDFTests.csproj", "{116308E4-C514-461A-B222-AEC05F1DFEFC}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -15,6 +17,10 @@ Global
 		{8BF6B775-F54A-4590-959B-FD6D5AEC1280}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8BF6B775-F54A-4590-959B-FD6D5AEC1280}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8BF6B775-F54A-4590-959B-FD6D5AEC1280}.Release|Any CPU.Build.0 = Release|Any CPU
+		{116308E4-C514-461A-B222-AEC05F1DFEFC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{116308E4-C514-461A-B222-AEC05F1DFEFC}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{116308E4-C514-461A-B222-AEC05F1DFEFC}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{116308E4-C514-461A-B222-AEC05F1DFEFC}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
diff --git a/MergePDF/App.config b/MergePDF/App.config
index 731f6de..ecdcf8a 100644
--- a/MergePDF/App.config
+++ b/MergePDF/App.config
@@ -1,6 +1,6 @@
-<?xml version="1.0" encoding="utf-8" ?>
+<?xml version="1.0" encoding="utf-8"?>
 <configuration>
     <startup> 
-        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2"/>
     </startup>
-</configuration>
\ No newline at end of file
+</configuration>
diff --git a/MergePDF/Form1.Designer.cs b/MergePDF/Form1.Designer.cs
index c54441c..a1b39b9 100644
--- a/MergePDF/Form1.Designer.cs
+++ b/MergePDF/Form1.Designer.cs
@@ -34,9 +34,13 @@ private void InitializeComponent()
             this.menuStrip1 = new System.Windows.Forms.MenuStrip();
             this.fileToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             this.exitToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
-            this.comboBox1 = new System.Windows.Forms.ComboBox();
             this.lblMergeAmount = new System.Windows.Forms.Label();
             this.btnClearAll = new System.Windows.Forms.Button();
+            this.flpFiles = new System.Windows.Forms.FlowLayoutPanel();
+            this.btnAddFile = new System.Windows.Forms.Button();
+            this.btnSaveFile = new System.Windows.Forms.Button();
+            this.txtSaveFile = new System.Windows.Forms.TextBox();
+            this.lblFileCount = new System.Windows.Forms.Label();
             this.menuStrip1.SuspendLayout();
             this.SuspendLayout();
             // 
@@ -84,28 +88,14 @@ private void InitializeComponent()
             // exitToolStripMenuItem
             // 
             this.exitToolStripMenuItem.Name = "exitToolStripMenuItem";
-            this.exitToolStripMenuItem.Size = new System.Drawing.Size(152, 22);
+            this.exitToolStripMenuItem.Size = new System.Drawing.Size(92, 22);
             this.exitToolStripMenuItem.Text = "Exit";
             this.exitToolStripMenuItem.Click += new System.EventHandler(this.exitToolStripMenuItem_Click);
             // 
-            // comboBox1
-            // 
-            this.comboBox1.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
-            this.comboBox1.FormattingEnabled = true;
-            this.comboBox1.Items.AddRange(new object[] {
-            "2",
-            "3",
-            "4"});
-            this.comboBox1.Location = new System.Drawing.Point(12, 63);
-            this.comboBox1.Name = "comboBox1";
-            this.comboBox1.Size = new System.Drawing.Size(604, 21);
-            this.comboBox1.TabIndex = 3;
-            this.comboBox1.SelectedIndexChanged += new System.EventHandler(this.comboBox1_SelectedIndexChanged);
-            // 
             // lblMergeAmount
             // 
             this.lblMergeAmount.AutoSize = true;
-            this.lblMergeAmount.Location = new System.Drawing.Point(9, 47);
+            this.lblMergeAmount.Location = new System.Drawing.Point(94, 44);
             this.lblMergeAmount.Name = "lblMergeAmount";
             this.lblMergeAmount.Size = new System.Drawing.Size(213, 13);
             this.lblMergeAmount.TabIndex = 4;
@@ -122,14 +112,62 @@ private void InitializeComponent()
             this.btnClearAll.UseVisualStyleBackColor = true;
             this.btnClearAll.Click += new System.EventHandler(this.btnClearAll_Click);
             // 
+            // flpFiles
+            // 
+            this.flpFiles.AutoScroll = true;
+            this.flpFiles.Location = new System.Drawing.Point(13, 68);
+            this.flpFiles.Name = "flpFiles";
+            this.flpFiles.Size = new System.Drawing.Size(603, 203);
+            this.flpFiles.TabIndex = 6;
+            // 
+            // btnAddFile
+            // 
+            this.btnAddFile.Location = new System.Drawing.Point(13, 39);
+            this.btnAddFile.Name = "btnAddFile";
+            this.btnAddFile.Size = new System.Drawing.Size(75, 23);
+            this.btnAddFile.TabIndex = 7;
+            this.btnAddFile.Text = "Add File";
+            this.btnAddFile.UseVisualStyleBackColor = true;
+            this.btnAddFile.Click += new System.EventHandler(this.btnAddFile_Click);
+            // 
+            // btnSaveFile
+            // 
+            this.btnSaveFile.Location = new System.Drawing.Point(13, 282);
+            this.btnSaveFile.Name = "btnSaveFile";
+            this.btnSaveFile.Size = new System.Drawing.Size(75, 23);
+            this.btnSaveFile.TabIndex = 8;
+            this.btnSaveFile.Text = "Save File at";
+            this.btnSaveFile.UseVisualStyleBackColor = true;
+            this.btnSaveFile.Click += new System.EventHandler(this.btnSaveFile_Click);
+            // 
+            // txtSaveFile
+            // 
+            this.txtSaveFile.Location = new System.Drawing.Point(106, 285);
+            this.txtSaveFile.Name = "txtSaveFile";
+            this.txtSaveFile.Size = new System.Drawing.Size(510, 20);
+            this.txtSaveFile.TabIndex = 9;
+            // 
+            // lblFileCount
+            // 
+            this.lblFileCount.AutoSize = true;
+            this.lblFileCount.Location = new System.Drawing.Point(308, 44);
+            this.lblFileCount.Name = "lblFileCount";
+            this.lblFileCount.Size = new System.Drawing.Size(13, 13);
+            this.lblFileCount.TabIndex = 10;
+            this.lblFileCount.Text = "0";
+            // 
             // Form1
             // 
             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
             this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
             this.ClientSize = new System.Drawing.Size(628, 481);
+            this.Controls.Add(this.lblFileCount);
+            this.Controls.Add(this.txtSaveFile);
+            this.Controls.Add(this.btnSaveFile);
+            this.Controls.Add(this.btnAddFile);
+            this.Controls.Add(this.flpFiles);
             this.Controls.Add(this.btnClearAll);
             this.Controls.Add(this.lblMergeAmount);
-            this.Controls.Add(this.comboBox1);
             this.Controls.Add(this.richConsole);
             this.Controls.Add(this.btnMergePdf);
             this.Controls.Add(this.menuStrip1);
@@ -155,9 +193,13 @@ private void InitializeComponent()
         private System.Windows.Forms.MenuStrip menuStrip1;
         private System.Windows.Forms.ToolStripMenuItem fileToolStripMenuItem;
         private System.Windows.Forms.ToolStripMenuItem exitToolStripMenuItem;
-        private System.Windows.Forms.ComboBox comboBox1;
         private System.Windows.Forms.Label lblMergeAmount;
         private System.Windows.Forms.Button btnClearAll;
+        private System.Windows.Forms.FlowLayoutPanel flpFiles;
+        private System.Windows.Forms.Button btnAddFile;
+        private System.Windows.Forms.Button btnSaveFile;
+        private System.Windows.Forms.TextBox txtSaveFile;
+        private System.Windows.Forms.Label lblFileCount;
     }
 }
 
diff --git a/MergePDF/Form1.cs b/MergePDF/Form1.cs
index ac317c6..20be783 100644
--- a/MergePDF/Form1.cs
+++ b/MergePDF/Form1.cs
@@ -20,14 +20,13 @@ public partial class Form1 : Form
         private List<TextBox> Textboxes { get; set; }
         private List<OpenFileDialog> FileDialogs { get; set; }
 
-        private List<string> Documents { get; set; }
-
-        // Create a document for the merged result.
-        private PdfDocument outDocument { get; set; }
+        private PdfMerger _pdfMerger;
 
         private OpenFileDialog openFileDialog { get; set; }
         private SaveFileDialog saveFileDialog { get; set; }
 
+        private int NumberOfFiles { get; set; }
+
         public Form1()
         {
             InitializeComponent();
@@ -35,7 +34,7 @@ public Form1()
             Buttons = new List<Button>();
             Textboxes = new List<TextBox>();
             FileDialogs = new List<OpenFileDialog>();
-            Documents = new List<string>();
+            _pdfMerger = new PdfMerger();
             CreateOpenFileDialog();
             CreateSaveFileDialog();
         }
@@ -51,33 +50,15 @@ private void richConsole_Enter(object sender, EventArgs e)
             ActiveControl = null;
         }
 
-        private void CopyPages(PdfDocument from, PdfDocument to)
-        {
-            for (int i = 0; i < from.PageCount; i++)
-            {
-                to.AddPage(from.Pages[i]);
-            }
-        }
-
         private void btnMergePdf_Click(object sender, EventArgs e)
         {
-
-            outDocument = new PdfDocument();
-
             try
             {
-                using (PdfDocument outPdf = new PdfDocument())
-                {
-                    foreach (var document in Documents)
-                    {
-                        document.Replace(@"\", "/");
-                        PdfDocument importPdf = PdfReader.Open(document, PdfDocumentOpenMode.Import);
-                        CopyPages(importPdf, outPdf);
-                    }
-                    var outputLocation = saveFileDialog.FileName.Replace(@"\", "/");
-                    outPdf.Save(outputLocation);
-                }
+                _pdfMerger.Clear();
+                foreach (var box in Textboxes)
+                    _pdfMerger.AddFile(box.Text);
 
+                _pdfMerger.MergeFiles(saveFileDialog.FileName);
                 richConsole.AppendText(string.Format("Merged successfully!\n"));
             }catch(Exception ex)
             {
@@ -97,36 +78,27 @@ private void clearToolStripMenuItem_Click(object sender, EventArgs e)
             richConsole.Clear();
         }
 
-        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
-        {
-            if (comboBox1.SelectedIndex == -1)
-                return;
-
-            btnMergePdf.Enabled = true;
-            ShowMergeRows(Int32.Parse(comboBox1.Items[comboBox1.SelectedIndex].ToString()));
-        }
-
         private void RemoveMergeRows()
         {
             foreach(var button in Buttons)
             {
-                Controls.Remove(button);
+                flpFiles.Controls.Remove(button);
             }
 
             foreach(var label in Labels)
             {
-                Controls.Remove(label);
+                flpFiles.Controls.Remove(label);
             }
 
             foreach(var txtBox in Textboxes)
             {
-                Controls.Remove(txtBox);
+                flpFiles.Controls.Remove(txtBox);
             }
 
             Buttons.Clear();
             Labels.Clear();
             Textboxes.Clear();
-            Documents.Clear();
+            _pdfMerger.Clear();
         }
 
         private void CreateOpenFileDialog()
@@ -162,94 +134,51 @@ private TextBox CreateTextbox(int yOffset)
             return textBox;
         }
 
-        private Button CreateSaveButton(int yOffset)
+        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
         {
-            Button button = new Button();
-            button.Location = new Point(10, yOffset);
-            button.Text = string.Format("Save file at");
-            button.Visible = true;
-
-            button.Click += (sender, e) =>
-            {
-                saveFileDialog.ShowDialog();
-                if (saveFileDialog.FileName != "")
-                {
-                    Textboxes.Last().Text = saveFileDialog.FileName;
-                    richConsole.AppendText(string.Format("Output location set: {0}\n", saveFileDialog.FileName));
-                }
-            };
-
-            Buttons.Add(button);
-
-            return button;
+            this.Close();
         }
 
-        private Button CreateOpenButton(int yOffset, int increment)
+        private void btnClearAll_Click(object sender, EventArgs e)
         {
-            Button button = new Button();
-            button.Location = new Point(10, yOffset);
-            button.Text = string.Format("Browse file {0}", increment + 1);
-            button.Visible = true;
+            lblFileCount.Text = (NumberOfFiles = 0).ToString();
+            RemoveMergeRows();
+            richConsole.Clear();
+            txtSaveFile.Text = string.Empty;
+            btnMergePdf.Enabled = false;
+        }
+
+        
 
-            button.Click += (sender, e) =>
+        private void btnAddFile_Click(object sender, EventArgs e)
+        {
+            var dialog = openFileDialog;
+            if (dialog.ShowDialog() == DialogResult.OK)
             {
-                var dialog = openFileDialog;
-                if (dialog.ShowDialog() == DialogResult.OK)
+                try
                 {
-                    try
-                    {
-                        string fileName = dialog.FileName;
-                        Documents.Add(fileName);
-                        Textboxes[increment].Text = fileName;
-                    }
-                    catch(System.IO.IOException)
-                    {
-                        MessageBox.Show("Uh-oh, something went wrong. Please try closing all the PDF files you want to import", "Import error", MessageBoxButtons.OK, MessageBoxIcon.Error);
-                        richConsole.AppendText("Something went wrong, please try closing all the PDF files you want to import first.\n");
-                    }
-                   
+                    lblFileCount.Text = (++NumberOfFiles).ToString();
+                    var box = CreateTextbox(45 * NumberOfFiles);
+                    box.Text = dialog.FileName;
+                    flpFiles.Controls.Add(box);
                 }
-            };
-
-            Buttons.Add(button);
-
-            return button;
+                catch (System.IO.IOException)
+                {
+                    MessageBox.Show("Uh-oh, something went wrong. Please try closing all the PDF files you want to import", "Import error", MessageBoxButtons.OK, MessageBoxIcon.Error);
+                    richConsole.AppendText("Something went wrong, please try closing all the PDF files you want to import first.\n");
+                }
+            }
+            btnMergePdf.Enabled = NumberOfFiles > 1;
         }
 
-        private void ShowMergeRows(int totalRows)
+        private void btnSaveFile_Click(object sender, EventArgs e)
         {
-            RemoveMergeRows();
-            int startY = 100;
-
-            for (int i = 0; i < totalRows; i++)
+            saveFileDialog.ShowDialog();
+            if (saveFileDialog.FileName != "")
             {
-                var textBox = CreateTextbox(startY);
-                Controls.Add(textBox);
-
-                var button = CreateOpenButton(startY, i);
-                Controls.Add(button);
-
-                startY += 45;
+                txtSaveFile.Text = saveFileDialog.FileName;
+                richConsole.AppendText(string.Format("Output location set: {0}\n", saveFileDialog.FileName));
             }
-
-            var saveTextBox = CreateTextbox(startY);
-            Controls.Add(saveTextBox);
-
-            var saveButton = CreateSaveButton(startY);
-            Controls.Add(saveButton);
-        }
-
-        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
-        {
-            this.Close();
-        }
-
-        private void btnClearAll_Click(object sender, EventArgs e)
-        {
-            RemoveMergeRows();
-            richConsole.Clear();
-            comboBox1.SelectedIndex = -1;
-            btnMergePdf.Enabled = false;
         }
     }
 }
diff --git a/MergePDF/MergePDF.csproj b/MergePDF/MergePDF.csproj
index be30e8f..00e3d59 100644
--- a/MergePDF/MergePDF.csproj
+++ b/MergePDF/MergePDF.csproj
@@ -9,7 +9,7 @@
     <OutputType>WinExe</OutputType>
     <RootNamespace>MergePDF</RootNamespace>
     <AssemblyName>MergePDF</AssemblyName>
-    <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <IsWebBootstrapper>false</IsWebBootstrapper>
@@ -29,6 +29,7 @@
     <BootstrapperEnabled>true</BootstrapperEnabled>
     <NuGetPackageImportStamp>
     </NuGetPackageImportStamp>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -81,6 +82,7 @@
     <Compile Include="Form1.Designer.cs">
       <DependentUpon>Form1.cs</DependentUpon>
     </Compile>
+    <Compile Include="PdfMerger.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <EmbeddedResource Include="Form1.resx">
@@ -94,6 +96,7 @@
     <Compile Include="Properties\Resources.Designer.cs">
       <AutoGen>True</AutoGen>
       <DependentUpon>Resources.resx</DependentUpon>
+      <DesignTime>True</DesignTime>
     </Compile>
     <None Include="packages.config">
       <SubType>Designer</SubType>
diff --git a/MergePDF/PdfMerger.cs b/MergePDF/PdfMerger.cs
new file mode 100644
index 0000000..f68a360
--- /dev/null
+++ b/MergePDF/PdfMerger.cs
@@ -0,0 +1,83 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using PdfSharp.Pdf;
+using PdfSharp.Pdf.IO;
+
+namespace MergePDF
+{
+    public class PdfMerger
+    {
+        public List<string> Documents { get; set; }
+        public string OutputFile { get; set; }
+
+        public PdfMerger()
+        {
+            Init();
+        }
+
+        private void Init()
+        {
+            Documents = new List<string>();
+            OutputFile = string.Empty;
+        }
+
+        public void Clear()
+        {
+            Init();
+        }
+
+        /// <summary>
+        /// Adds a pdf filepath/filename
+        /// </summary>
+        /// <param name="filename"></param>
+        public void AddFile(string filename)
+        {
+            Documents.Add(filename);
+        }
+
+        /// <summary>
+        /// Merges pdf files
+        /// </summary>
+        /// <param name="outputFile">optionally set outputfile here</param>
+        public void MergeFiles(string outputFile = null)
+        {
+            try
+            {
+                if (outputFile != null)
+                    OutputFile = outputFile;
+                if (Documents?.Count < 2)
+                    throw new Exception("Two or more files are required to merge!");
+                if ((OutputFile ?? string.Empty) == string.Empty)
+                    throw new Exception("Output file not set!");
+
+                var outDocument = new PdfDocument();
+
+                using (PdfDocument outPdf = new PdfDocument())
+                {
+                    foreach (var document in Documents)
+                    {
+                        PdfDocument importPdf = PdfReader.Open(document.Replace(@"\", "/"), PdfDocumentOpenMode.Import);
+                        CopyPages(importPdf, outPdf);
+                    }
+                    var outputLocation = OutputFile.Replace(@"\", "/");
+                    outPdf.Save(outputLocation);
+                }
+            }
+            catch (Exception)
+            {
+                throw;
+            }
+        }
+
+        private void CopyPages(PdfDocument from, PdfDocument to)
+        {
+            for (int i = 0; i < from.PageCount; i++)
+            {
+                to.AddPage(from.Pages[i]);
+            }
+        }
+    }
+}
diff --git a/MergePDF/Properties/Resources.Designer.cs b/MergePDF/Properties/Resources.Designer.cs
index e1ae42c..b78b3ef 100644
--- a/MergePDF/Properties/Resources.Designer.cs
+++ b/MergePDF/Properties/Resources.Designer.cs
@@ -8,10 +8,10 @@
 // </auto-generated>
 //------------------------------------------------------------------------------
 
-namespace MergePDF.Properties
-{
-
-
+namespace MergePDF.Properties {
+    using System;
+    
+    
     /// <summary>
     ///   A strongly-typed resource class, for looking up localized strings, etc.
     /// </summary>
@@ -19,51 +19,43 @@ namespace MergePDF.Properties
     // class via a tool like ResGen or Visual Studio.
     // To add or remove a member, edit your .ResX file then rerun ResGen
     // with the /str option, or rebuild your VS project.
-    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "4.0.0.0")]
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "15.0.0.0")]
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
     [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
-    internal class Resources
-    {
-
+    internal class Resources {
+        
         private static global::System.Resources.ResourceManager resourceMan;
-
+        
         private static global::System.Globalization.CultureInfo resourceCulture;
-
+        
         [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
-        internal Resources()
-        {
+        internal Resources() {
         }
-
+        
         /// <summary>
         ///   Returns the cached ResourceManager instance used by this class.
         /// </summary>
         [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
-        internal static global::System.Resources.ResourceManager ResourceManager
-        {
-            get
-            {
-                if ((resourceMan == null))
-                {
+        internal static global::System.Resources.ResourceManager ResourceManager {
+            get {
+                if (object.ReferenceEquals(resourceMan, null)) {
                     global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("MergePDF.Properties.Resources", typeof(Resources).Assembly);
                     resourceMan = temp;
                 }
                 return resourceMan;
             }
         }
-
+        
         /// <summary>
         ///   Overrides the current thread's CurrentUICulture property for all
         ///   resource lookups using this strongly typed resource class.
         /// </summary>
         [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)]
-        internal static global::System.Globalization.CultureInfo Culture
-        {
-            get
-            {
+        internal static global::System.Globalization.CultureInfo Culture {
+            get {
                 return resourceCulture;
             }
-            set
-            {
+            set {
                 resourceCulture = value;
             }
         }
diff --git a/MergePDF/Properties/Settings.Designer.cs b/MergePDF/Properties/Settings.Designer.cs
index e6c71b2..61a239d 100644
--- a/MergePDF/Properties/Settings.Designer.cs
+++ b/MergePDF/Properties/Settings.Designer.cs
@@ -8,21 +8,17 @@
 // </auto-generated>
 //------------------------------------------------------------------------------
 
-namespace MergePDF.Properties
-{
-
-
+namespace MergePDF.Properties {
+    
+    
     [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
-    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "11.0.0.0")]
-    internal sealed partial class Settings : global::System.Configuration.ApplicationSettingsBase
-    {
-
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "15.8.0.0")]
+    internal sealed partial class Settings : global::System.Configuration.ApplicationSettingsBase {
+        
         private static Settings defaultInstance = ((Settings)(global::System.Configuration.ApplicationSettingsBase.Synchronized(new Settings())));
-
-        public static Settings Default
-        {
-            get
-            {
+        
+        public static Settings Default {
+            get {
                 return defaultInstance;
             }
         }
diff --git a/MergePDFTests/MergePDFTests.csproj b/MergePDFTests/MergePDFTests.csproj
new file mode 100644
index 0000000..d3ffeb0
--- /dev/null
+++ b/MergePDFTests/MergePDFTests.csproj
@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.props" Condition="Exists('..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.props')" />
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{116308E4-C514-461A-B222-AEC05F1DFEFC}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>MergePDFTests</RootNamespace>
+    <AssemblyName>MergePDFTests</AssemblyName>
+    <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+    <ProjectTypeGuids>{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">15.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+    <ReferencePath>$(ProgramFiles)\Common Files\microsoft shared\VSTT\$(VisualStudioVersion)\UITestExtensionPackages</ReferencePath>
+    <IsCodedUITest>False</IsCodedUITest>
+    <TestProjectType>UnitTest</TestProjectType>
+    <NuGetPackageImportStamp>
+    </NuGetPackageImportStamp>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <HintPath>..\packages\MSTest.TestFramework.1.3.2\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.dll</HintPath>
+    </Reference>
+    <Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <HintPath>..\packages\MSTest.TestFramework.1.3.2\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions.dll</HintPath>
+    </Reference>
+    <Reference Include="PdfSharp, Version=1.50.4820.0, Culture=neutral, PublicKeyToken=f94615aa0424f9eb, processorArchitecture=MSIL">
+      <HintPath>..\packages\PDFsharp.1.50.4820-RC1\lib\net20\PdfSharp.dll</HintPath>
+    </Reference>
+    <Reference Include="PdfSharp.Charting, Version=1.50.4820.0, Culture=neutral, PublicKeyToken=f94615aa0424f9eb, processorArchitecture=MSIL">
+      <HintPath>..\packages\PDFsharp.1.50.4820-RC1\lib\net20\PdfSharp.Charting.dll</HintPath>
+    </Reference>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Drawing" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="UnitTests.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+    <None Include="TestFiles\test_1.pdf" />
+    <None Include="TestFiles\test_2.pdf" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\MergePDF\MergePDF.csproj">
+      <Project>{8bf6b775-f54a-4590-959b-fd6d5aec1280}</Project>
+      <Name>MergePDF</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets" Condition="Exists('$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets')" />
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
+    <PropertyGroup>
+      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
+    </PropertyGroup>
+    <Error Condition="!Exists('..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.props'))" />
+    <Error Condition="!Exists('..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.targets'))" />
+  </Target>
+  <Import Project="..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.targets" Condition="Exists('..\packages\MSTest.TestAdapter.1.3.2\build\net45\MSTest.TestAdapter.targets')" />
+</Project>
\ No newline at end of file
diff --git a/MergePDFTests/Properties/AssemblyInfo.cs b/MergePDFTests/Properties/AssemblyInfo.cs
new file mode 100644
index 0000000..3743a03
--- /dev/null
+++ b/MergePDFTests/Properties/AssemblyInfo.cs
@@ -0,0 +1,20 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+[assembly: AssemblyTitle("MergePDFTests")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("MergePDFTests")]
+[assembly: AssemblyCopyright("Copyright ©  2018")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+[assembly: ComVisible(false)]
+
+[assembly: Guid("116308e4-c514-461a-b222-aec05f1dfefc")]
+
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]
diff --git a/MergePDFTests/TestFiles/test_1.pdf b/MergePDFTests/TestFiles/test_1.pdf
new file mode 100644
index 0000000..3ae70ad
Binary files /dev/null and b/MergePDFTests/TestFiles/test_1.pdf differ
diff --git a/MergePDFTests/TestFiles/test_2.pdf b/MergePDFTests/TestFiles/test_2.pdf
new file mode 100644
index 0000000..b9f6a42
Binary files /dev/null and b/MergePDFTests/TestFiles/test_2.pdf differ
diff --git a/MergePDFTests/UnitTests.cs b/MergePDFTests/UnitTests.cs
new file mode 100644
index 0000000..fd36c65
--- /dev/null
+++ b/MergePDFTests/UnitTests.cs
@@ -0,0 +1,80 @@
+using System;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MergePDF;
+using PdfSharp.Pdf.IO;
+
+namespace MergePDFTests
+{
+    [TestClass]
+    public class UnitTests
+    {
+        private const string PDF_TEST_FILE_1 = @"..\..\TestFiles\test_1.pdf";
+        private const string PDF_TEST_FILE_2 = @"..\..\TestFiles\test_2.pdf";
+        private const string PDF_OUT = "out.pdf";
+
+        [TestMethod]
+        public void Merge_with_no_files_Fail()
+        {
+            PdfMerger pdfMerger = new PdfMerger();
+            Assert.ThrowsException<Exception>(() => pdfMerger.MergeFiles());
+        }
+
+        [TestMethod]
+        public void Merge_with_not_enough_files_Fail()
+        {
+            PdfMerger pdfMerger = new PdfMerger();
+            pdfMerger.AddFile(PDF_TEST_FILE_1);
+
+            if (System.IO.File.Exists(PDF_OUT))
+                System.IO.File.Delete(PDF_OUT);
+
+            Assert.ThrowsException<Exception>(() => pdfMerger.MergeFiles(PDF_OUT));
+        }
+
+        [TestMethod]
+        public void Merge_with_no_out_file_Fail()
+        {
+            PdfMerger pdfMerger = new PdfMerger();
+            pdfMerger.AddFile(PDF_TEST_FILE_1);
+            pdfMerger.AddFile(PDF_TEST_FILE_2);
+
+            if (System.IO.File.Exists(PDF_OUT))
+                System.IO.File.Delete(PDF_OUT);
+
+            Assert.ThrowsException<Exception>(() => pdfMerger.MergeFiles());
+        }
+
+        [TestMethod]
+        public void Merge_files_Pass()
+        {
+            PdfMerger pdfMerger = new PdfMerger();
+            pdfMerger.AddFile(PDF_TEST_FILE_1);
+            pdfMerger.AddFile(PDF_TEST_FILE_2);
+
+            if (System.IO.File.Exists(PDF_OUT))
+                System.IO.File.Delete(PDF_OUT);
+
+            pdfMerger.MergeFiles(PDF_OUT);
+
+            Assert.IsTrue(System.IO.File.Exists(PDF_OUT));
+        }
+
+        [TestMethod]
+        public void Merge_files_pageCount_verify_Pass()
+        {
+            PdfMerger pdfMerger = new PdfMerger();
+            pdfMerger.AddFile(PDF_TEST_FILE_1);
+            pdfMerger.AddFile(PDF_TEST_FILE_2);
+            pdfMerger.AddFile(PDF_TEST_FILE_1);
+            pdfMerger.AddFile(PDF_TEST_FILE_2);
+
+            if (System.IO.File.Exists(PDF_OUT))
+                System.IO.File.Delete(PDF_OUT);
+
+            pdfMerger.MergeFiles(PDF_OUT);
+
+            var count = PdfReader.Open(PDF_OUT.Replace(@"\", "/"), PdfDocumentOpenMode.Import).PageCount;
+            Assert.AreEqual(pdfMerger.Documents.Count, count);
+        }
+    }
+}
diff --git a/MergePDFTests/packages.config b/MergePDFTests/packages.config
new file mode 100644
index 0000000..a5b64ae
--- /dev/null
+++ b/MergePDFTests/packages.config
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<packages>
+  <package id="MSTest.TestAdapter" version="1.3.2" targetFramework="net472" />
+  <package id="MSTest.TestFramework" version="1.3.2" targetFramework="net472" />
+  <package id="PDFsharp" version="1.50.4820-RC1" targetFramework="net472" />
+</packages>
\ No newline at end of file