diff --git a/Parser.Tests/MParserShould.cs b/Parser.Tests/MParserShould.cs
index 06f020c..bb1fb01 100644
--- a/Parser.Tests/MParserShould.cs
+++ b/Parser.Tests/MParserShould.cs
@@ -1,4 +1,4 @@
-using NUnit.Framework;
+using Xunit;
 
 namespace Parser.Tests
 {
@@ -11,26 +11,26 @@ namespace Parser.Tests
             return parser;
         }
         
-        [Test]
+        [Fact]
         public void ParseAssignmentExpression()
         {
             var text = "a = b";
             var sut = GetSut(text);
             var actual = sut.Parse();
             var assignment = actual.Root.StatementList[0].AsNode();
-            Assert.IsInstanceOf<ExpressionStatementSyntaxNode>(assignment);
-            Assert.IsInstanceOf<AssignmentExpressionSyntaxNode>(((ExpressionStatementSyntaxNode)assignment).Expression);
+            Assert.IsType<ExpressionStatementSyntaxNode>(assignment);
+            Assert.IsType<AssignmentExpressionSyntaxNode>(((ExpressionStatementSyntaxNode)assignment).Expression);
         }
 
-        [Test]
+        [Fact]
         public void ParseAssignmentExpression_Incomplete()
         {
             var text = "a = ";
             var sut = GetSut(text);
             var actual = sut.Parse();
             var assignment = actual.Root.StatementList[0].AsNode();
-            Assert.IsInstanceOf<ExpressionStatementSyntaxNode>(assignment);
-            Assert.IsInstanceOf<AssignmentExpressionSyntaxNode>(((ExpressionStatementSyntaxNode)assignment).Expression);
+            Assert.IsType<ExpressionStatementSyntaxNode>(assignment);
+            Assert.IsType<AssignmentExpressionSyntaxNode>(((ExpressionStatementSyntaxNode)assignment).Expression);
         }
     }
 }
\ No newline at end of file
diff --git a/Parser.Tests/Parser.Tests.csproj b/Parser.Tests/Parser.Tests.csproj
index bf1772c..0dcbb0e 100644
--- a/Parser.Tests/Parser.Tests.csproj
+++ b/Parser.Tests/Parser.Tests.csproj
@@ -5,8 +5,8 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.7.0" />
-    <PackageReference Include="NUnit" Version="3.10.1" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.10.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Parser\Parser.csproj" />
diff --git a/Parser.Tests/TextWindowShould.cs b/Parser.Tests/TextWindowShould.cs
index 82f1b97..bbf33e3 100644
--- a/Parser.Tests/TextWindowShould.cs
+++ b/Parser.Tests/TextWindowShould.cs
@@ -1,36 +1,35 @@
-using NUnit.Framework;
+using Xunit;
 
 namespace Parser.Tests
 {
-    [TestFixture]
     public class TestWindowShould
     {
-        [Test]
+        [Fact]
         public void ReturnEofGivenEmptyText()
         {
             var sut = new TextWindow("");
-            Assert.IsTrue(sut.IsEof());
+            Assert.True(sut.IsEof());
         }
 
-        [Test]
+        [Fact]
         public void ReturnNotEofGivenNonEmptyText()
         {
             var sut = new TextWindow("Text.");
-            Assert.IsFalse(sut.IsEof());
+            Assert.False(sut.IsEof());
         }
 
-        [Test]
+        [Fact]
         public void ReturnCharsInCorrectOrder()
         {
             var text = "abc";
             var sut = new TextWindow(text);
-            Assert.AreEqual('a', sut.PeekChar());
+            Assert.Equal('a', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.AreEqual('b', sut.PeekChar());
+            Assert.Equal('b', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.AreEqual('c', sut.PeekChar());
+            Assert.Equal('c', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.IsTrue(sut.IsEof());
+            Assert.True(sut.IsEof());
         }
     }
 }
\ No newline at end of file
diff --git a/Parser.Tests/TextWindowWithNullShould.cs b/Parser.Tests/TextWindowWithNullShould.cs
index 20c4b46..66f432a 100644
--- a/Parser.Tests/TextWindowWithNullShould.cs
+++ b/Parser.Tests/TextWindowWithNullShould.cs
@@ -1,29 +1,28 @@
-using NUnit.Framework;
+using Xunit;
 
 namespace Parser.Tests
 {
-    [TestFixture]
     public class TestWindowWithNullShould
     {
-        [Test]
+        [Fact]
         public void ReturnNullGivenEmptyText()
         {
             var sut = new TextWindowWithNull("");
-            Assert.IsTrue(sut.PeekChar() == '\0');
+            Assert.True(sut.PeekChar() == '\0');
         }
 
-        [Test]
+        [Fact]
         public void ReturnCharsInCorrectOrder()
         {
             var text = "abc";
             var sut = new TextWindowWithNull(text);
-            Assert.AreEqual('a', sut.PeekChar());
+            Assert.Equal('a', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.AreEqual('b', sut.PeekChar());
+            Assert.Equal('b', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.AreEqual('c', sut.PeekChar());
+            Assert.Equal('c', sut.PeekChar());
             sut.ConsumeChar();
-            Assert.AreEqual('\0', sut.PeekChar());
+            Assert.Equal('\0', sut.PeekChar());
         }
     }
 }
\ No newline at end of file
diff --git a/Parser.Tests/ThereAndBackAgain.cs b/Parser.Tests/ThereAndBackAgain.cs
index 3c36a92..fa0097c 100644
--- a/Parser.Tests/ThereAndBackAgain.cs
+++ b/Parser.Tests/ThereAndBackAgain.cs
@@ -1,7 +1,7 @@
 using System;
-using NUnit.Framework;
 using System.Collections.Generic;
 using System.IO;
+using Xunit;
 
 namespace Parser.Tests
 {
@@ -49,7 +49,7 @@ namespace Parser.Tests
             var parser = CreateParser(window);
             var tree = parser.Parse();
             var actual = tree.Root.FullText;
-            Assert.That(actual == text);
+            Assert.Equal(text, actual);
         }
 
         private static void ProcessDirectory(string directory)
@@ -72,8 +72,7 @@ namespace Parser.Tests
             }
         }
 
-        [Category("Slow")]
-        [Test]
+        [Fact]
         public void TestEverything()
         {
             ProcessDirectory(BaseDirectory);