Migrate test framework from NUnit to xUnit

CLAUDE.md

@@ -9,7 +9,7 @@ dotnet test EulerLibTests/EulerLibTests.csproj
 ## Structure
 - **Euler/** - Console runner app (net8.0)
 - **EulerLib/** - Problem solutions library. Each problem implements `IProblem` (`Id`, `Title`, `Solve()`, `Md5OfSolution`)
-- **EulerLibTests/** - Test project (NUnit + FluentAssertions + AutoFixture)
+- **EulerLibTests/** - Test project (xUnit + FluentAssertions + AutoFixture)
 
 ## Conventions
 - Problems go in `EulerLib/Problems/0001_0100/Problem0001.cs` (namespace `EulerLib.Problems`)

EulerLibTests/EulerLibTests.csproj

@@ -10,9 +10,12 @@
     <PackageReference Include="AutoFixture" Version="4.18.1" />
     <PackageReference Include="FluentAssertions" Version="8.8.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.3.0" />
-    <PackageReference Include="NUnit" Version="4.5.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="6.1.0" />
-    <PackageReference Include="NUnit.Analyzers" Version="4.11.2">
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+    <PackageReference Include="xunit.analyzers" Version="1.18.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>

EulerLibTests/Extensions/BigIntegerExtensionsFixture.cs

@@ -3,11 +3,11 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class BigIntegerExtensionsFixture
 {
-    [TestCase("12345", 15)]
-    [TestCase("1234567890", 45)]
+    [Theory]
+    [InlineData("12345", 15)]
+    [InlineData("1234567890", 45)]
     public void SumOfDigits_Tests(string value, int expectedSumOfDigits)
     {
         var bigint = BigInteger.Parse(value);

EulerLibTests/Extensions/DivisorsExtensionFixture.cs

@@ -2,15 +2,15 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class DivisorsExtensionFixture
 {
-    [TestCase(1, 1, 1)]
-    [TestCase(2, 3, 2)]
-    [TestCase(4, 7, 3)]
-    [TestCase(16, 31, 5)]
-    [TestCase(220, 504, 12)]
-    [TestCase(284, 504, 6)]
+    [Theory]
+    [InlineData(1, 1, 1)]
+    [InlineData(2, 3, 2)]
+    [InlineData(4, 7, 3)]
+    [InlineData(16, 31, 5)]
+    [InlineData(220, 504, 12)]
+    [InlineData(284, 504, 6)]
     public void DivisorsTests(int n, int divisorsSum, int divisorsCount)
     {
         // Arrange
@@ -19,16 +19,17 @@ public void DivisorsTests(int n, int divisorsSum, int divisorsCount)
         var divisors = n.Divisors();
 
         // Assert
-        Assert.That(divisors.Count(), Is.EqualTo(divisorsCount));
-        Assert.That(divisors.Sum(), Is.EqualTo(divisorsSum));
+        divisors.Count().Should().Be(divisorsCount);
+        divisors.Sum().Should().Be(divisorsSum);
     }
 
-    [TestCase(1, 0, 0)]
-    [TestCase(2, 1, 1)]
-    [TestCase(4, 3, 2)]
-    [TestCase(16, 15, 4)]
-    [TestCase(220, 284, 11)]
-    [TestCase(284, 220, 5)]
+    [Theory]
+    [InlineData(1, 0, 0)]
+    [InlineData(2, 1, 1)]
+    [InlineData(4, 3, 2)]
+    [InlineData(16, 15, 4)]
+    [InlineData(220, 284, 11)]
+    [InlineData(284, 220, 5)]
     public void ProperDivisorsTests(int n, int divisorsSum, int divisorsCount)
     {
         // Arrange
@@ -37,11 +38,12 @@ public void ProperDivisorsTests(int n, int divisorsSum, int divisorsCount)
         var divisors = n.ProperDivisors();
 
         // Assert
-        Assert.That(divisors.Count(), Is.EqualTo(divisorsCount));
-        Assert.That(divisors.Sum(), Is.EqualTo(divisorsSum));
+        divisors.Count().Should().Be(divisorsCount);
+        divisors.Sum().Should().Be(divisorsSum);
     }
 
-    [TestCase(4, new[] { 1, 2 })]
+    [Theory]
+    [InlineData(4, new[] { 1, 2 })]
     public void ProperDivisors_ValuesTest(int n, int[] expectedDivisors)
     {
         var divisors = n.ProperDivisors();

EulerLibTests/Extensions/IntegerExtensionsFixture.cs

@@ -2,37 +2,37 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class IntegerExtensionsFixture
 {
-    [TestCase(2, "2")]
-    [TestCase(3, "6")]
-    [TestCase(4, "24")]
-    [TestCase(5, "120")]
+    [Theory]
+    [InlineData(2, "2")]
+    [InlineData(3, "6")]
+    [InlineData(4, "24")]
+    [InlineData(5, "120")]
     public void FactorialTests(int n, string expectedFactorial)
     {
         var result = n.Factorial();
 
         result.ToString().Should().Be(expectedFactorial);
     }
 
-    [Test]
+    [Fact]
     public void DigitRotationsTest2845()
     {
         var result = 2845.DigitRotations().ToList();
 
         result.Should().BeEquivalentTo([2845, 8452, 4528, 5284]);
     }
 
-    [Test]
+    [Fact]
     public void DigitRotationsTest197()
     {
         var result = 197.DigitRotations().ToList();
 
         result.Should().BeEquivalentTo([197, 971, 719]);
     }
 
-    [Test]
+    [Fact]
     public void DigitRotationsTest111()
     {
         var result = 111.DigitRotations().ToList();

EulerLibTests/Extensions/Md5ExtensionsFixture.cs

@@ -2,19 +2,20 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class Md5ExtensionsFixture
 {
-    [TestCase("Hello World!", "ed076287532e86365e841e92bfc50d8c")]
+    [Theory]
+    [InlineData("Hello World!", "ed076287532e86365e841e92bfc50d8c")]
     public void ToMd5Hash(string input, string expectedHash)
     {
         var hash = input.ToMd5Hash();
 
         hash.Should().Be(expectedHash);
     }
 
-    [TestCase("Hello World!", "ed076287532e86365e841e92bfc50d8c", true)]
-    [TestCase("Hello World!", "ed076287532e86355e841e92bfc50d8c", false)]
+    [Theory]
+    [InlineData("Hello World!", "ed076287532e86365e841e92bfc50d8c", true)]
+    [InlineData("Hello World!", "ed076287532e86355e841e92bfc50d8c", false)]
     public void VerifyMd5Hash(string input, string hash, bool expectedResult)
     {
         var result = input.VerifyMd5Hash(hash);

EulerLibTests/Extensions/PrimeFactorsExtensionFixture.cs

@@ -2,37 +2,36 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class PrimeFactorsExtensionFixture
 {
-    [Test]
+    [Fact]
     public void PrimeFactorsOf1()
     {
         var sequence = 1.PrimeFactors().ToList();
 
         sequence.Should().BeEmpty();
     }
 
-    [Test]
+    [Fact]
     public void PrimeFactorsOf12()
     {
         var sequence = 12.PrimeFactors().ToList();
 
         sequence.Should().BeEquivalentTo(new[] {2, 2, 3});
     }
 
-    [Test]
+    [Fact]
     public void PrimeFactorsOf13195()
     {
         var sequence = 13195.PrimeFactors().ToList();
 
         sequence.Should().BeEquivalentTo(new[] {5, 7, 13, 29});
     }
 
-    [Test]
+    [Fact]
     public void PrimeFactorsOfFirst3500Numbers()
     {
         IEnumerable<long> result = null;
 
         for (int i = 1; i <= 3500; i++)
         {

EulerLibTests/Extensions/RomanNumeralsExtensionsFixture.cs

@@ -2,55 +2,59 @@
 
 namespace EulerLibTests.Extensions;
 
-[TestFixture]
 public class RomanNumeralsExtensionsFixture
 {
-    [TestCase("XXFX", "F")]
-    [TestCase("C%C", "%")]
+    [Theory]
+    [InlineData("XXFX", "F")]
+    [InlineData("C%C", "%")]
     public void ParseRomanNumeral_InvalidRomanCharacter_Throws(string input, string expectedInvalidCharacter)
     {
         var ex = Assert.Throws<ArgumentException>(() => input.ParseRomanNumeral());
 
         ex.Message.Should().Contain("Invalid Roman numeral character: " + expectedInvalidCharacter);
     }
 
-    [TestCase("I", 1)]
-    [TestCase("II", 2)]
-    [TestCase("III", 3)]
-    [TestCase("IV", 4)]
-    [TestCase("LVII", 57)]
-    [TestCase("MMMMCCLXXXVI", 4286)]
+    [Theory]
+    [InlineData("I", 1)]
+    [InlineData("II", 2)]
+    [InlineData("III", 3)]
+    [InlineData("IV", 4)]
+    [InlineData("LVII", 57)]
+    [InlineData("MMMMCCLXXXVI", 4286)]
     public void ParseRomanNumeral_ValidInput_ReturnsExpectedResult(string input, int expectedResult)
     {
         var result = input.ParseRomanNumeral();
 
         result.Should().Be(expectedResult);
     }
 
-    [TestCase(-5)]
-    [TestCase(0)]
-    [TestCase(5000)]
-    [TestCase(9678)]
+    [Theory]
+    [InlineData(-5)]
+    [InlineData(0)]
+    [InlineData(5000)]
+    [InlineData(9678)]
     public void ToRomanNumeral_OutOfRange_Throws(int value)
     {
         var ex = Assert.Throws<ArgumentOutOfRangeException>(() => value.ToRomanNumeral());
 
         ex.Message.Should().Contain("Input must be between 1 and 4999.");
     }
 
-    [TestCase(1, "I")]
-    [TestCase(2, "II")]
-    [TestCase(4, "IV")]
-    [TestCase(19, "XIX")]
-    [TestCase(2024, "MMXXIV")]
+    [Theory]
+    [InlineData(1, "I")]
+    [InlineData(2, "II")]
+    [InlineData(4, "IV")]
+    [InlineData(19, "XIX")]
+    [InlineData(2024, "MMXXIV")]
     public void ToRomanNumeral_ValidInput_ReturnsExpectedResult(int value, string expectedResult)
     {
         var result = value.ToRomanNumeral();
 
         result.Should().Be(expectedResult);
     }
 
-    [TestCase("XIIII", "XIV")]
+    [Theory]
+    [InlineData("XIIII", "XIV")]
     public void SimplifyRomanNumeral_ValidInput_ReturnsExpectedOutput(string value, string expectedResult)
     {
         var result = value.SimplifyRomanNumeral();