diff --git a/X10D.Tests/src/Core/CoreTests.cs b/X10D.Tests/src/Core/CoreTests.cs
new file mode 100644
index 0000000..1ce041e
--- /dev/null
+++ b/X10D.Tests/src/Core/CoreTests.cs
@@ -0,0 +1,27 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using X10D.Core;
+using X10D.Text;
+
+namespace X10D.Tests.Core;
+
+[TestClass]
+public class CoreTests
+{
+    [TestMethod]
+    public void AsArrayShouldBeLength1()
+    {
+        Assert.AreEqual(1, 0.AsArray().Length);
+        Assert.AreEqual(1, string.Empty.AsArray().Length);
+        Assert.AreEqual(1, true.AsArray().Length);
+        Assert.AreEqual(1, ((object?)null).AsArray().Length);
+    }
+    
+    [TestMethod]
+    public void AsEnumerableShouldBeLength1()
+    {
+        Assert.AreEqual(1, 0.AsEnumerable().Count());
+        Assert.AreEqual(1, string.Empty.AsEnumerable().Count());
+        Assert.AreEqual(1, true.AsEnumerable().Count());
+        Assert.AreEqual(1, ((object?)null).AsEnumerable().Count());
+    }
+}