Migrate test framework from NUnit to xUnit

Replace NUnit 4.5 with xUnit 2.9.3 across all 56 test files. Update test attributes ([TestFixture] → auto-discovery, [Test] → [Fact], [TestCase] → [Theory]/[InlineData]) and convert assertions to xUnit syntax with correct parameter ordering (expected, actual). All 182 tests passing.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ianfnelson

AdventOfCodeTests/AdventOfCodeTests.csproj

@@ -11,16 +11,15 @@
     <ItemGroup>
         <PackageReference Include="coverlet.collector" Version="8.0.0"/>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
-        <PackageReference Include="NUnit" Version="4.5.0" />
-        <PackageReference Include="NUnit.Analyzers" Version="4.11.2">
+        <PackageReference Include="xunit" Version="2.9.3" />
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
           <PrivateAssets>all</PrivateAssets>
           <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
-        <PackageReference Include="NUnit3TestAdapter" Version="6.1.0" />
     </ItemGroup>
 
     <ItemGroup>
-        <Using Include="NUnit.Framework"/>
+        <Using Include="Xunit"/>
     </ItemGroup>
 
     <ItemGroup>

AdventOfCodeTests/Events/2018/Day01Tests.cs

@@ -0,0 +1,33 @@
+using AdventOfCode.Events._2018.Days;
+
+namespace AdventOfCodeTests.Events._2018.Days;
+
+public class Day01Tests
+{
+    [Theory]
+    [InlineData("+1, +1, +1", "3")]
+    [InlineData("+1, +1, -2", "0")]
+    [InlineData("-1, -2, -3", "-6")]
+    public void Part1Test(string inputString, string expectedOutput)
+    {
+        var input = inputString.Split(", ");
+
+        var output = Day01.Part1Impl(input);
+
+        Assert.Equal(expectedOutput, output);
+    }
+
+    [Theory]
+    [InlineData("+1, -1", "0")]
+    [InlineData("+3, +3, +4, -2, -4", "10")]
+    [InlineData("-6, +3, +8, +5, -6", "5")]
+    [InlineData("+7, +7, -2, -7, -4", "14")]
+    public void Part2Test(string inputString, string expectedOutput)
+    {
+        var input = inputString.Split(", ");
+
+        var output = Day01.Part2Impl(input);
+
+        Assert.Equal(expectedOutput, output);
+    }
+}

AdventOfCodeTests/Events/2018/Days/Day01Tests.cs

@@ -2,28 +2,29 @@
 
 namespace AdventOfCodeTests.Events._2019.Days;
 
-[TestFixture]
 public class Day01Tests
 {
-    [TestCase(12, 2)]
-    [TestCase(14, 2)]
-    [TestCase(1969, 654)]
-    [TestCase(100756, 33583)]
+    [Theory]
+    [InlineData(12, 2)]
+    [InlineData(14, 2)]
+    [InlineData(1969, 654)]
+    [InlineData(100756, 33583)]
     public void Module_FuelCalculation_Part1(int mass, int expectedFuel)
     {
         var sut = new Day01.Module(mass);
-        
-        Assert.That(sut.FuelRequirement(false), Is.EqualTo(expectedFuel));
+
+        Assert.Equal(expectedFuel, sut.FuelRequirement(false));
     }
-    
-    [TestCase(12, 2)]
-    [TestCase(14, 2)]
-    [TestCase(1969, 966)]
-    [TestCase(100756, 50346)]
+
+    [Theory]
+    [InlineData(12, 2)]
+    [InlineData(14, 2)]
+    [InlineData(1969, 966)]
+    [InlineData(100756, 50346)]
     public void Module_FuelCalculation_Part2(int mass, int expectedFuel)
     {
         var sut = new Day01.Module(mass);
-        
-        Assert.That(sut.FuelRequirement(true), Is.EqualTo(expectedFuel));
+
+        Assert.Equal(expectedFuel, sut.FuelRequirement(true));
     }
 }

AdventOfCodeTests/Events/2019/Days/Day01Tests.cs

@@ -2,21 +2,21 @@
 
 namespace AdventOfCodeTests.Events._2019.Days;
 
-[TestFixture]
 public class Day02Tests
 {
-    [TestCase("1,0,0,0,99","2,0,0,0,99")]
-    [TestCase("2,3,0,3,99","2,3,0,6,99")]
-    [TestCase("2,4,4,5,99,0","2,4,4,5,99,9801")]
-    [TestCase("1,1,1,4,99,5,6,0,99","30,1,1,4,2,5,6,0,99")]
+    [Theory]
+    [InlineData("1,0,0,0,99","2,0,0,0,99")]
+    [InlineData("2,3,0,3,99","2,3,0,6,99")]
+    [InlineData("2,4,4,5,99,0","2,4,4,5,99,9801")]
+    [InlineData("1,1,1,4,99,5,6,0,99","30,1,1,4,2,5,6,0,99")]
     public void Computer_Run_Part1(string input, string expectedOutput)
     {
         var sut = new Day02.Computer();
-        
+
         sut.Program(input);
-        
+
         sut.Run();
-        
-        Assert.That(sut.ToString(), Is.EqualTo(expectedOutput));
+
+        Assert.Equal(expectedOutput, sut.ToString());
     }
 }

AdventOfCodeTests/Events/2019/Days/Day02Tests.cs

@@ -2,22 +2,23 @@
 
 namespace AdventOfCodeTests.Events._2019.Days;
 
-[TestFixture]
 public class Day04Tests
 {
-    [TestCase(111111,true)]
-    [TestCase(223450,false)]
-    [TestCase(123789,false)]
+    [Theory]
+    [InlineData(111111,true)]
+    [InlineData(223450,false)]
+    [InlineData(123789,false)]
     public void MeetsCriteriaPart1(int value, bool expectedResult)
     {
-        Assert.That(Day04.MeetsCriteria(value, 1), Is.EqualTo(expectedResult));
+        Assert.Equal(expectedResult, Day04.MeetsCriteria(value, 1));
     }
-    
-    [TestCase(112233,true)]
-    [TestCase(123444,false)]
-    [TestCase(111122,true)]
+
+    [Theory]
+    [InlineData(112233,true)]
+    [InlineData(123444,false)]
+    [InlineData(111122,true)]
     public void MeetsCriteriaPart2(int value, bool expectedResult)
     {
-        Assert.That(Day04.MeetsCriteria(value, 2), Is.EqualTo(expectedResult));
+        Assert.Equal(expectedResult, Day04.MeetsCriteria(value, 2));
     }
 }

AdventOfCodeTests/Events/2019/Days/Day04Tests.cs

@@ -2,20 +2,19 @@
 
 namespace AdventOfCodeTests.Events._2020.Days;
 
-[TestFixture]
 public class Day01Tests
 {
     private readonly Day01 _systemUnderTest = new();
-    
-    [Test]
+
+    [Fact]
     public void Part1Test()
     {
-        Assert.That(_systemUnderTest.Part1("Events/2020/TestData/1.txt"), Is.EqualTo("514579"));
+        Assert.Equal("514579", _systemUnderTest.Part1("Events/2020/TestData/1.txt"));
     }
-    
-    [Test]
+
+    [Fact]
     public void Part2Test()
     {
-        Assert.That(_systemUnderTest.Part2("Events/2020/TestData/1.txt"), Is.EqualTo("241861950"));
+        Assert.Equal("241861950", _systemUnderTest.Part2("Events/2020/TestData/1.txt"));
     }
 }

AdventOfCodeTests/Events/2020/Days/Day01Tests.cs

@@ -2,20 +2,19 @@
 
 namespace AdventOfCodeTests.Events._2021.Days;
 
-[TestFixture]
 public class Day01Tests
 {
     private readonly Day01 _systemUnderTest = new();
 
-    [Test]
+    [Fact]
     public void Part1Test()
     {
-        Assert.That(_systemUnderTest.Part1("Events/2021/TestData/1.txt"), Is.EqualTo("7"));
+        Assert.Equal("7", _systemUnderTest.Part1("Events/2021/TestData/1.txt"));
     }
-    
-    [Test]
+
+    [Fact]
     public void Part2Test()
     {
-        Assert.That(_systemUnderTest.Part2("Events/2021/TestData/1.txt"), Is.EqualTo("5"));
+        Assert.Equal("5", _systemUnderTest.Part2("Events/2021/TestData/1.txt"));
     }
 }

AdventOfCodeTests/Events/2021/Days/Day01Tests.cs

@@ -2,20 +2,19 @@
 
 namespace AdventOfCodeTests.Events._2022.Days;
 
-[TestFixture]
 public class Day01Tests
 {
     private readonly Day01 _systemUnderTest = new();
-    
-    [Test]
+
+    [Fact]
     public void Part1Test()
     {
-        Assert.That(_systemUnderTest.Part1("Events/2022/TestData/1.txt"), Is.EqualTo("24000"));
+        Assert.Equal("24000", _systemUnderTest.Part1("Events/2022/TestData/1.txt"));
     }
-    
-    [Test]
+
+    [Fact]
     public void Part2Test()
     {
-        Assert.That(_systemUnderTest.Part2("Events/2022/TestData/1.txt"), Is.EqualTo("45000"));
+        Assert.Equal("45000", _systemUnderTest.Part2("Events/2022/TestData/1.txt"));
     }
 }

AdventOfCodeTests/Events/2022/Days/Day01Tests.cs

@@ -2,20 +2,19 @@
 
 namespace AdventOfCodeTests.Events._2022.Days;
 
-[TestFixture]
 public class Day02Tests
 {
     private readonly Day02 _systemUnderTest = new();
-    
-    [Test]
+
+    [Fact]
     public void Part1Test()
     {
-        Assert.That(_systemUnderTest.Part1("Events/2022/TestData/2.txt"), Is.EqualTo("15"));
+        Assert.Equal("15", _systemUnderTest.Part1("Events/2022/TestData/2.txt"));
     }
-    
-    [Test]
+
+    [Fact]
     public void Part2Test()
     {
-        Assert.That(_systemUnderTest.Part2("Events/2022/TestData/2.txt"), Is.EqualTo("12"));
+        Assert.Equal("12", _systemUnderTest.Part2("Events/2022/TestData/2.txt"));
     }
 }