diff --git a/X10D.Tests/src/Collections/EnumerableTests.cs b/X10D.Tests/src/Collections/EnumerableTests.cs
index 6d990ee..4e95f49 100644
--- a/X10D.Tests/src/Collections/EnumerableTests.cs
+++ b/X10D.Tests/src/Collections/EnumerableTests.cs
@@ -1,4 +1,4 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using X10D.Collections;
 
 namespace X10D.Tests.Collections;
@@ -6,6 +6,64 @@ namespace X10D.Tests.Collections;
 [TestClass]
 public class EnumerableTests
 {
+    [TestMethod]
+    public void For_ShouldTransform_GivenTransformationDelegate()
+    {
+        var oneToTen = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+        var multipliedByIndex = new[] {0, 2, 6, 12, 20, 30, 42, 56, 72, 90};
+
+        IEnumerable<DummyClass> source = oneToTen.Select(i => new DummyClass {Value = i}).ToArray();
+        IEnumerable<int> values = source.Select(o => o.Value);
+        CollectionAssert.AreEqual(oneToTen, values.ToArray());
+
+        source.For((i, o) => o.Value *= i);
+        values = source.Select(o => o.Value);
+        CollectionAssert.AreEqual(multipliedByIndex, values.ToArray());
+    }
+
+    [TestMethod]
+    public void For_ShouldThrow_GivenNullSource()
+    {
+        IEnumerable<object>? source = null;
+        Assert.ThrowsException<ArgumentNullException>(() => source!.For((_, _) => { }));
+    }
+
+    [TestMethod]
+    public void For_ShouldThrow_GivenNullAction()
+    {
+        IEnumerable<object> source = ArraySegment<object>.Empty;
+        Assert.ThrowsException<ArgumentNullException>(() => source.For(null!));
+    }
+
+    [TestMethod]
+    public void ForEach_ShouldTransform_GivenTransformationDelegate()
+    {
+        var oneToTen = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+        var oneToTenDoubled = new[] {2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
+
+        IEnumerable<DummyClass> source = oneToTen.Select(i => new DummyClass {Value = i}).ToArray();
+        IEnumerable<int> values = source.Select(o => o.Value);
+        CollectionAssert.AreEqual(oneToTen, values.ToArray());
+
+        source.ForEach(o => o.Value *= 2);
+        values = source.Select(o => o.Value);
+        CollectionAssert.AreEqual(oneToTenDoubled, values.ToArray());
+    }
+
+    [TestMethod]
+    public void ForEach_ShouldThrow_GivenNullSource()
+    {
+        IEnumerable<object>? source = null;
+        Assert.ThrowsException<ArgumentNullException>(() => source!.ForEach(_ => { }));
+    }
+
+    [TestMethod]
+    public void ForEach_ShouldThrow_GivenNullAction()
+    {
+        IEnumerable<object> source = ArraySegment<object>.Empty;
+        Assert.ThrowsException<ArgumentNullException>(() => source.ForEach(null!));
+    }
+
     [TestMethod]
     public void Shuffled_ShouldThrow_GivenNull()
     {
@@ -23,4 +81,9 @@ public class EnumerableTests
         shuffled = array.Shuffled().ToArray();
         CollectionAssert.AreNotEqual(array, shuffled);
     }
+
+    private class DummyClass
+    {
+        public int Value { get; set; }
+    }
 }
diff --git a/X10D.Tests/src/Core/EnumerableTests.cs b/X10D.Tests/src/Core/EnumerableTests.cs
deleted file mode 100644
index 8e85c2f..0000000
--- a/X10D.Tests/src/Core/EnumerableTests.cs
+++ /dev/null
@@ -1,84 +0,0 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
-using X10D.Collections;
-using X10D.Core;
-
-namespace X10D.Tests.Core;
-
-[TestClass]
-public class EnumerableTests
-{
-    [TestMethod]
-    [DataRow(1)]
-    [DataRow("f")]
-    [DataRow(true)]
-    public void AsEnumerable_ShouldWrapElement_GivenValue(object o)
-    {
-        IEnumerable<object?> array = o.AsEnumerableValue().ToArray(); // prevent multiple enumeration of IEnumerable
-        Assert.IsNotNull(array);
-        Assert.IsTrue(array.Count() == 1);
-        Assert.AreEqual(o, array.ElementAt(0));
-    }
-
-    [TestMethod]
-    public void For_ShouldTransform_GivenTransformationDelegate()
-    {
-        var oneToTen = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
-        var multipliedByIndex = new[] {0, 2, 6, 12, 20, 30, 42, 56, 72, 90};
-
-        IEnumerable<DummyClass> source = oneToTen.Select(i => new DummyClass {Value = i}).ToArray();
-        IEnumerable<int> values = source.Select(o => o.Value);
-        CollectionAssert.AreEqual(oneToTen, values.ToArray());
-
-        source.For((i, o) => o.Value *= i);
-        values = source.Select(o => o.Value);
-        CollectionAssert.AreEqual(multipliedByIndex, values.ToArray());
-    }
-
-    [TestMethod]
-    public void For_ShouldThrow_GivenNullSource()
-    {
-        IEnumerable<object>? source = null;
-        Assert.ThrowsException<ArgumentNullException>(() => source!.For((_, _) => { }));
-    }
-
-    [TestMethod]
-    public void For_ShouldThrow_GivenNullAction()
-    {
-        IEnumerable<object> source = ArraySegment<object>.Empty;
-        Assert.ThrowsException<ArgumentNullException>(() => source.For(null!));
-    }
-
-    [TestMethod]
-    public void ForEach_ShouldTransform_GivenTransformationDelegate()
-    {
-        var oneToTen = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
-        var oneToTenDoubled = new[] {2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
-
-        IEnumerable<DummyClass> source = oneToTen.Select(i => new DummyClass {Value = i}).ToArray();
-        IEnumerable<int> values = source.Select(o => o.Value);
-        CollectionAssert.AreEqual(oneToTen, values.ToArray());
-
-        source.ForEach(o => o.Value *= 2);
-        values = source.Select(o => o.Value);
-        CollectionAssert.AreEqual(oneToTenDoubled, values.ToArray());
-    }
-
-    [TestMethod]
-    public void ForEach_ShouldThrow_GivenNullSource()
-    {
-        IEnumerable<object>? source = null;
-        Assert.ThrowsException<ArgumentNullException>(() => source!.ForEach(_ => { }));
-    }
-
-    [TestMethod]
-    public void ForEach_ShouldThrow_GivenNullAction()
-    {
-        IEnumerable<object> source = ArraySegment<object>.Empty;
-        Assert.ThrowsException<ArgumentNullException>(() => source.ForEach(null!));
-    }
-
-    private class DummyClass
-    {
-        public int Value { get; set; }
-    }
-}