diff --git a/src/CollectionExtensions.cs b/src/CollectionExtensions.cs
index 69fd4fc..2fe500f 100644
--- a/src/CollectionExtensions.cs
+++ b/src/CollectionExtensions.cs
@@ -10,6 +10,7 @@ public static class CollectionExtensions
     /// </summary>
     public static void AddRange<T>(this ICollection<T> self, IEnumerable<T> items)
     {
+        ArgumentNullException.ThrowIfNull(self);
         ArgumentNullException.ThrowIfNull(items);
         switch (self)
         {
@@ -27,4 +28,24 @@ public static void AddRange<T>(this ICollection<T> self, IEnumerable<T> items)
                 break;
         }
     }
+
+    /// <summary>
+    /// Removes the list item at the specified index.
+    /// </summary>
+    public static void RemoveAt<T>(this IList<T> self, Index index)
+    {
+        ArgumentNullException.ThrowIfNull(self);
+        var offset = index.GetOffset(self.Count);
+        self.RemoveAt(offset);
+    }
+
+    /// <summary>
+    /// Removes the list item at the specified range.
+    /// </summary>
+    public static void RemoveRange<T>(this List<T> self, Range range)
+    {
+        ArgumentNullException.ThrowIfNull(self);
+        var (offset, length) = range.GetOffsetAndLength(self.Count);
+        self.RemoveRange(offset, length);
+    }
 }
diff --git a/src/EnumerablePlus/LinqEnumerablePlus.cs b/src/EnumerablePlus/LinqEnumerablePlus.cs
index 4d4a3cd..60b95ea 100644
--- a/src/EnumerablePlus/LinqEnumerablePlus.cs
+++ b/src/EnumerablePlus/LinqEnumerablePlus.cs
@@ -253,25 +253,25 @@ public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> source, Random? rand
         switch (source)
         {
             case ICollection<T> collection:
-            {
-                var copy = collection.ToArray();
-                random.Shuffle(copy);
-                return copy;
-            }
+                {
+                    var copy = collection.ToArray();
+                    random.Shuffle(copy);
+                    return copy;
+                }
             case IReadOnlyCollection<T> readOnly:
-            {
-                int count = readOnly.Count;
-                if (count == 0)
-                    return Array.Empty<T>();
-
-                var result = new T[count];
-                var index = 0;
-                foreach (var item in readOnly)
-                    result[index++] = item;
-
-                random.Shuffle(result);
-                return result;
-            }
+                {
+                    int count = readOnly.Count;
+                    if (count == 0)
+                        return Array.Empty<T>();
+
+                    var result = new T[count];
+                    var index = 0;
+                    foreach (var item in readOnly)
+                        result[index++] = item;
+
+                    random.Shuffle(result);
+                    return result;
+                }
             default:
                 return source.OrderBy(_ => random.Next());
         }
diff --git a/src/RangeExtension.cs b/src/RangeExtension.cs
index 3cc676e..dd623e5 100644
--- a/src/RangeExtension.cs
+++ b/src/RangeExtension.cs
@@ -137,8 +137,8 @@ public static IEnumerable<TResult> SelectMany<TResult>(
         Func<int, int, TResult> project)
     {
         foreach (var n1 in range)
-        foreach (var n2 in projection(n1))
-            yield return project(n1, n2);
+            foreach (var n2 in projection(n1))
+                yield return project(n1, n2);
     }
 
     /// <summary>
diff --git a/tests/CSharpPlus.Tests/CollectionExtensionsTests.cs b/tests/CSharpPlus.Tests/CollectionExtensionsTests.cs
new file mode 100644
index 0000000..8725340
--- /dev/null
+++ b/tests/CSharpPlus.Tests/CollectionExtensionsTests.cs
@@ -0,0 +1,60 @@
+namespace CSharpPlus.Tests;
+
+#pragma warning disable S6605
+#pragma warning disable S6602
+
+public class CollectionExtensionsTests
+{
+    [Test]
+    public void ShouldAddRange()
+    {
+        List<int> currentItems = [1, 2, 3];
+        int[] newItems = [4, 5, 6];
+        int[] expected = [1, 2, 3, 4, 5, 6];
+
+        currentItems.AddRange(newItems);
+        currentItems.Should().BeEquivalentTo(expected);
+    }
+
+    [Test]
+    public void ShouldRemoveRange()
+    {
+        List<int> currentItems = [1, 2, 3, 4, 5, 6];
+        int[] expected = [1, 2, 3];
+        var removeRange = 3..6;
+
+        currentItems.RemoveRange(removeRange);
+        currentItems.Should().BeEquivalentTo(expected);
+    }
+
+    [Test]
+    public void ShouldRemoveRangeMid()
+    {
+        List<int> currentItems = [1, 2, 3, 4, 5, 6];
+        int[] expected = [1, 6];
+        var removeRange = 1..^1;
+
+        currentItems.RemoveRange(removeRange);
+        currentItems.Should().BeEquivalentTo(expected);
+    }
+
+    [Test]
+    public void ShouldRemoveLast()
+    {
+        List<int> currentItems = [1, 2, 3, 4];
+        int[] expected = [1, 2, 3];
+
+        currentItems.RemoveAt(^1);
+        currentItems.Should().BeEquivalentTo(expected);
+    }
+
+    [Test]
+    public void ShouldRemoveBeforeLast()
+    {
+        List<int> currentItems = [1, 2, 3, 4];
+        int[] expected = [1, 2, 4];
+
+        currentItems.RemoveAt(^2);
+        currentItems.Should().BeEquivalentTo(expected);
+    }
+}