diff --git a/Kyoo.Common/Utility/EnumerableExtensions.cs b/Kyoo.Common/Utility/EnumerableExtensions.cs
index e4d0379e..459d5f1c 100644
--- a/Kyoo.Common/Utility/EnumerableExtensions.cs
+++ b/Kyoo.Common/Utility/EnumerableExtensions.cs
@@ -18,13 +18,13 @@ namespace Kyoo
 		/// <param name="mapper">The function that will map each items</param>
 		/// <typeparam name="T">The type of items in <see cref="self"/></typeparam>
 		/// <typeparam name="T2">The type of items in the returned list</typeparam>
-		/// <returns>The list mapped or null if the input map was null.</returns>
-		/// <exception cref="ArgumentNullException">mapper can't be null</exception>
-		public static IEnumerable<T2> Map<T, T2>([CanBeNull] this IEnumerable<T> self, 
+		/// <returns>The list mapped.</returns>
+		/// <exception cref="ArgumentNullException">The list or the mapper can't be null</exception>
+		public static IEnumerable<T2> Map<T, T2>([NotNull] this IEnumerable<T> self, 
 			[NotNull] Func<T, int, T2> mapper)
 		{
 			if (self == null)
-				return null;
+				throw new ArgumentNullException(nameof(self));
 			if (mapper == null)
 				throw new ArgumentNullException(nameof(mapper));
 
@@ -46,28 +46,33 @@ namespace Kyoo
 		/// A map where the mapping function is asynchronous.
 		/// Note: <see cref="SelectAsync{T,T2}"/> might interest you. 
 		/// </summary>
-		/// <param name="self">The IEnumerable to map. If self is null, an empty list is returned</param>
+		/// <param name="self">The IEnumerable to map.</param>
 		/// <param name="mapper">The asynchronous function that will map each items</param>
 		/// <typeparam name="T">The type of items in <see cref="self"/></typeparam>
 		/// <typeparam name="T2">The type of items in the returned list</typeparam>
 		/// <returns>The list mapped as an AsyncEnumerable</returns>
-		/// <exception cref="ArgumentNullException">mapper can't be null</exception>
-		public static async IAsyncEnumerable<T2> MapAsync<T, T2>([CanBeNull] this IEnumerable<T> self, 
+		/// <exception cref="ArgumentNullException">The list or the mapper can't be null</exception>
+		public static IAsyncEnumerable<T2> MapAsync<T, T2>([NotNull] this IEnumerable<T> self, 
 			[NotNull] Func<T, int, Task<T2>> mapper)
 		{
 			if (self == null)
-				yield break;
+				throw new ArgumentNullException(nameof(self));
 			if (mapper == null)
 				throw new ArgumentNullException(nameof(mapper));
-			
-			using IEnumerator<T> enumerator = self.GetEnumerator();
-			int index = 0;
 
-			while (enumerator.MoveNext())
+			static async IAsyncEnumerable<T2> Generator(IEnumerable<T> self, Func<T, int, Task<T2>> mapper)
 			{
-				yield return await mapper(enumerator.Current, index);
-				index++;
+				using IEnumerator<T> enumerator = self.GetEnumerator();
+				int index = 0;
+
+				while (enumerator.MoveNext())
+				{
+					yield return await mapper(enumerator.Current, index);
+					index++;
+				}
 			}
+
+			return Generator(self, mapper);
 		}
 		
 		/// <summary>
@@ -78,19 +83,24 @@ namespace Kyoo
 		/// <typeparam name="T">The type of items in <see cref="self"/></typeparam>
 		/// <typeparam name="T2">The type of items in the returned list</typeparam>
 		/// <returns>The list mapped as an AsyncEnumerable</returns>
-		/// <exception cref="ArgumentNullException">mapper can't be null</exception>
-		public static async IAsyncEnumerable<T2> SelectAsync<T, T2>([CanBeNull] this IEnumerable<T> self, 
+		/// <exception cref="ArgumentNullException">The list or the mapper can't be null</exception>
+		public static IAsyncEnumerable<T2> SelectAsync<T, T2>([NotNull] this IEnumerable<T> self, 
 			[NotNull] Func<T, Task<T2>> mapper)
 		{
 			if (self == null)
-				yield break;
+				throw new ArgumentNullException(nameof(self));
 			if (mapper == null)
 				throw new ArgumentNullException(nameof(mapper));
-			
-			using IEnumerator<T> enumerator = self.GetEnumerator();
 
-			while (enumerator.MoveNext())
-				yield return await mapper(enumerator.Current);
+			static async IAsyncEnumerable<T2> Generator(IEnumerable<T> self, Func<T, Task<T2>> mapper)
+			{
+				using IEnumerator<T> enumerator = self.GetEnumerator();
+
+				while (enumerator.MoveNext())
+					yield return await mapper(enumerator.Current);
+			}
+
+			return Generator(self, mapper);
 		}
 
 		/// <summary>
@@ -100,16 +110,20 @@ namespace Kyoo
 		/// <typeparam name="T">The type of items in the async list and in the returned list.</typeparam>
 		/// <returns>A task that will return a simple list</returns>
 		/// <exception cref="ArgumentNullException">The list can't be null</exception>
-		public static async Task<List<T>> ToListAsync<T>([NotNull] this IAsyncEnumerable<T> self)
+		public static Task<List<T>> ToListAsync<T>([NotNull] this IAsyncEnumerable<T> self)
 		{
 			if (self == null)
 				throw new ArgumentNullException(nameof(self));
-			
-			List<T> ret = new();
-			
-			await foreach(T i in self)
-				ret.Add(i);
-			return ret;
+
+			static async Task<List<T>> ToList(IAsyncEnumerable<T> self)
+			{
+				List<T> ret = new();
+				await foreach (T i in self)
+					ret.Add(i);
+				return ret;
+			}
+
+			return ToList(self);
 		}
 
 		/// <summary>
@@ -118,22 +132,33 @@ namespace Kyoo
 		/// <param name="self">The enumerable to check</param>
 		/// <param name="action">The action to execute is the list is empty</param>
 		/// <typeparam name="T">The type of items inside the list</typeparam>
-		/// <returns></returns>
-		public static IEnumerable<T> IfEmpty<T>(this IEnumerable<T> self, Action action)
+		/// <exception cref="ArgumentNullException">The iterable and the action can't be null.</exception>
+		/// <returns>The iterator proxied, there is no dual iterations.</returns>
+		public static IEnumerable<T> IfEmpty<T>([NotNull] this IEnumerable<T> self, [NotNull] Action action)
 		{
-			using IEnumerator<T> enumerator = self.GetEnumerator();
+			if (self == null)
+				throw new ArgumentNullException(nameof(self));
+			if (action == null)
+				throw new ArgumentNullException(nameof(action));
 
-			if (!enumerator.MoveNext())
+			static IEnumerable<T> Generator(IEnumerable<T> self, Action action)
 			{
-				action();
-				yield break;
+				using IEnumerator<T> enumerator = self.GetEnumerator();
+
+				if (!enumerator.MoveNext())
+				{
+					action();
+					yield break;
+				}
+
+				do
+				{
+					yield return enumerator.Current;
+				} 
+				while (enumerator.MoveNext());
 			}
-			
-			do
-			{
-				yield return enumerator.Current;
-			}
-			while (enumerator.MoveNext());
+
+			return Generator(self, action);
 		}
 
 		/// <summary>
diff --git a/Kyoo.Tests/KAssert.cs b/Kyoo.Tests/KAssert.cs
index b6168251..2c97ddce 100644
--- a/Kyoo.Tests/KAssert.cs
+++ b/Kyoo.Tests/KAssert.cs
@@ -1,14 +1,41 @@
 using System.Reflection;
 using Xunit;
+using Xunit.Sdk;
 
 namespace Kyoo.Tests
 {
+	/// <summary>
+	/// Custom assertions used by Kyoo's tests.
+	/// </summary>
 	public static class KAssert
 	{
+		/// <summary>
+		/// Check if every property of the item is equal to the other's object.
+		/// </summary>
+		/// <param name="expected">The value to check against</param>
+		/// <param name="value">The value to check</param>
+		/// <typeparam name="T">The type to check</typeparam>
 		public static void DeepEqual<T>(T expected, T value)
 		{
 			foreach (PropertyInfo property in typeof(T).GetProperties())
 				Assert.Equal(property.GetValue(expected), property.GetValue(value));
 		}
+
+		/// <summary>
+		/// Explicitly fail a test.
+		/// </summary>
+		public static void Fail()
+		{
+			throw new XunitException();
+		}
+		
+		/// <summary>
+		/// Explicitly fail a test.
+		/// </summary>
+		/// <param name="message">The message that will be seen in the test report</param>
+		public static void Fail(string message)
+		{
+			throw new XunitException(message);
+		}
 	}
 }
\ No newline at end of file
diff --git a/Kyoo.Tests/Utility/EnumerableTests.cs b/Kyoo.Tests/Utility/EnumerableTests.cs
new file mode 100644
index 00000000..9cdd8a00
--- /dev/null
+++ b/Kyoo.Tests/Utility/EnumerableTests.cs
@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Kyoo.Tests
+{
+	public class EnumerableTests
+	{
+		[Fact]
+		public void MapTest()
+		{
+			int[] list = {1, 2, 3, 4};
+			Assert.All(list.Map((x, i) => (x, i)), x => Assert.Equal(x.x - 1, x.i));
+			Assert.Throws<ArgumentNullException>(() => list.Map(((Func<int, int, int>)null)!));
+			list = null;
+			Assert.Throws<ArgumentNullException>(() => list!.Map((x, _) => x + 1));
+		}
+		
+		[Fact]
+		public async Task MapAsyncTest()
+		{
+			int[] list = {1, 2, 3, 4};
+			await foreach((int x, int i) in list.MapAsync((x, i) => Task.FromResult((x, i))))
+			{
+				Assert.Equal(x - 1, i);
+			}
+			Assert.Throws<ArgumentNullException>(() => list.MapAsync(((Func<int, int, Task<int>>)null)!));
+			list = null;
+			Assert.Throws<ArgumentNullException>(() => list!.MapAsync((x, _) => Task.FromResult(x + 1)));
+		}
+		
+		[Fact]
+		public async Task SelectAsyncTest()
+		{
+			int[] list = {1, 2, 3, 4};
+			int i = 2;
+			await foreach(int x in list.SelectAsync(x => Task.FromResult(x + 1)))
+			{
+				Assert.Equal(i++, x);
+			}
+			Assert.Throws<ArgumentNullException>(() => list.SelectAsync(((Func<int, Task<int>>)null)!));
+			list = null;
+			Assert.Throws<ArgumentNullException>(() => list!.SelectAsync(x => Task.FromResult(x + 1)));
+		}
+		
+		[Fact]
+		public async Task ToListAsyncTest()
+		{
+			int[] expected = {1, 2, 3, 4};
+			IAsyncEnumerable<int> list = expected.SelectAsync(Task.FromResult);
+			Assert.Equal(expected, await list.ToListAsync());
+			list = null;
+			await Assert.ThrowsAsync<ArgumentNullException>(() => list!.ToListAsync());
+		}
+		
+		[Fact]
+		public void IfEmptyTest()
+		{
+			int[] list = {1, 2, 3, 4};
+			list = list.IfEmpty(() => KAssert.Fail("Empty action should not be triggered.")).ToArray();
+			Assert.Throws<ArgumentNullException>(() => list.IfEmpty(null!).ToList());
+			list = null;
+			Assert.Throws<ArgumentNullException>(() => list!.IfEmpty(() => {}).ToList());
+			list = Array.Empty<int>();
+			Assert.Throws<ArgumentException>(() => list.IfEmpty(() => throw new ArgumentException()).ToList());
+			Assert.Empty(list.IfEmpty(() => {}));
+		}
+	}
+}
\ No newline at end of file