diff --git a/AdventOfCode.HelperClasses.Tests/AdventOfCode.HelperClasses.Tests.csproj b/AdventOfCode.HelperClasses.Tests/AdventOfCode.HelperClasses.Tests.csproj
new file mode 100644
index 0000000..280d23c
--- /dev/null
+++ b/AdventOfCode.HelperClasses.Tests/AdventOfCode.HelperClasses.Tests.csproj
@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net9.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <IsPackable>false</IsPackable>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="coverlet.collector" Version="6.0.2"/>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0"/>
+        <PackageReference Include="xunit" Version="2.9.2"/>
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2"/>
+    </ItemGroup>
+
+    <ItemGroup>
+        <Using Include="Xunit"/>
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\AdventOfCode.HelperClasses\AdventOfCode.HelperClasses.csproj" />
+    </ItemGroup>
+
+</Project>
diff --git a/AdventOfCode.HelperClasses.Tests/IntegerRangeTests.cs b/AdventOfCode.HelperClasses.Tests/IntegerRangeTests.cs
new file mode 100644
index 0000000..6d0e442
--- /dev/null
+++ b/AdventOfCode.HelperClasses.Tests/IntegerRangeTests.cs
@@ -0,0 +1,60 @@
+namespace AdventOfCode.HelperClasses.Tests;
+
+public class IntegerRangeTests
+{
+    private readonly IntegerRange _sut;
+    public IntegerRangeTests()
+    {
+        _sut = new IntegerRange(1, 10);
+    }
+    
+    [Fact]
+    public void Range1_10_Count_equals_10()
+    {
+        var actual = _sut.Count;
+        
+        Assert.Equal(10, actual);
+    }
+    
+    [Theory]
+    [InlineData(10)]
+    [InlineData(1)]
+    [InlineData(5)]
+    public void Range1_10_Contains_data_is_true(int data)
+    {
+        var actual = _sut.Contains(data);
+        
+        Assert.True(actual);
+    }
+    
+    [Theory]
+    [InlineData(10)]
+    [InlineData(1)]
+    [InlineData(5)]
+    [InlineData(11)]
+    [InlineData(20)]
+    [InlineData(15)]
+    public void CombinedRange1_20_Contains_data_is_true(int data)
+    {
+        var actual = _sut.TryCombine(new  IntegerRange(11, 20), out var combined);
+        Assert.True(actual);
+        actual = combined.Contains(data);
+        Assert.True(actual);
+    }
+
+    [Fact]
+    public void First_equals_1()
+    {
+        var actual = _sut.First();
+        
+        Assert.Equal(1, actual);
+    }
+    
+    [Fact]
+    public void Last_equals_10()
+    {
+        var actual = _sut.Last();
+        
+        Assert.Equal(10, actual);
+    }
+}
\ No newline at end of file
diff --git a/AdventOfCode.HelperClasses/IntegerRange.cs b/AdventOfCode.HelperClasses/IntegerRange.cs
index 59b4d31..c4e8810 100644
--- a/AdventOfCode.HelperClasses/IntegerRange.cs
+++ b/AdventOfCode.HelperClasses/IntegerRange.cs
@@ -1,21 +1,23 @@
-namespace AdventOfCode.HelperClasses;
+using System.Collections;
 
-public record IntegerRange(long start, long end)
+namespace AdventOfCode.HelperClasses;
+
+public record IntegerRange(long start, long end) : IEnumerable<long>
 {
-    public long Count() => end - start + 1;
+    public long Count => end - start + 1;
 
     public bool Contains(long number) => start <= number && end >= number;
 
     public bool TryCombine(IntegerRange other, out IntegerRange combined)
     {
-        if (Contains(other.start))
+        if (Contains(other.start) || other.start == end + 1)
         {
             var isEndInRange = Contains(other.end);
             combined = isEndInRange ? this : this with {end = other.end};
             return true;
         }
         
-        if (other.Contains(start))
+        if (other.Contains(start) || start == other.end + 1)
         {
             var isEndInRange = other.Contains(end);
             combined = isEndInRange ? other : other with {end = end};
@@ -25,4 +27,34 @@ public record IntegerRange(long start, long end)
         combined = this;
         return false;
     }
+
+    public IEnumerator<long> GetEnumerator() => new IntegerRangeEnumerator(start, end);
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+}
+
+public record IntegerRangeEnumerator(long start, long end) : IEnumerator<long>
+{
+    private long _current = start - 1;
+
+    public bool MoveNext()
+    {
+        if(_current >= end) return false;
+        _current++;
+        return true;
+    }
+
+    public void Reset()
+    {
+        _current = start - 1;
+    }
+
+    long IEnumerator<long>.Current => _current;
+
+    object? IEnumerator.Current => _current;
+
+    public void Dispose()
+    {
+        GC.SuppressFinalize(this);
+    }
 }
\ No newline at end of file
diff --git a/AdventOfCode.sln b/AdventOfCode.sln
index 7ca1055..645a128 100644
--- a/AdventOfCode.sln
+++ b/AdventOfCode.sln
@@ -14,6 +14,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AdventOfCode.Extensions", "
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AdventOfCode.HelperClasses", "AdventOfCode.HelperClasses\AdventOfCode.HelperClasses.csproj", "{D47175BB-5AD6-43A8-9287-FF5E6F1816E3}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AdventOfCode.HelperClasses.Tests", "AdventOfCode.HelperClasses.Tests\AdventOfCode.HelperClasses.Tests.csproj", "{3D09528A-09A7-4B0B-9D45-7D3AAB26449A}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -44,6 +46,10 @@ Global
 		{D47175BB-5AD6-43A8-9287-FF5E6F1816E3}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D47175BB-5AD6-43A8-9287-FF5E6F1816E3}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D47175BB-5AD6-43A8-9287-FF5E6F1816E3}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3D09528A-09A7-4B0B-9D45-7D3AAB26449A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3D09528A-09A7-4B0B-9D45-7D3AAB26449A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3D09528A-09A7-4B0B-9D45-7D3AAB26449A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3D09528A-09A7-4B0B-9D45-7D3AAB26449A}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{4F395AE3-DABB-4546-A4D0-5A62425FE168} = {05EBAA1C-B33B-4AFE-8635-A58D7CA509A7}
diff --git a/AoC_2025/Day05.cs b/AoC_2025/Day05.cs
index a682d0b..5b1d895 100644
--- a/AoC_2025/Day05.cs
+++ b/AoC_2025/Day05.cs
@@ -106,7 +106,7 @@ public class Day05 : IPuzzleSolver<long>
     
     private static IEnumerable<long> CountIdsInRanges(IEnumerable<IntegerRange> combinedRanges)
     {
-        var countIdsInRanges = combinedRanges.Select(range => range.Count());
+        var countIdsInRanges = combinedRanges.Select(range => range.Count);
         return countIdsInRanges;
     }
 }
\ No newline at end of file