Added unit test project for HelperClasses and tests for IntegerRange.cs. Implemented IEnumerable on IntegerRange.

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);
+    }
+}