diff --git a/spec/cbor_simple-values.cr b/spec/cbor_simple-values.cr
new file mode 100644
index 0000000..f35c85a
--- /dev/null
+++ b/spec/cbor_simple-values.cr
@@ -0,0 +1,15 @@
+require "./spec_helper"
+
+describe CBOR do
+  describe "basics: to_cbor" do
+    it "union (Nil | Bool) (nil)" do
+      value = (Nil | Bool).from_cbor(nil.to_cbor).to_cbor
+      value.hexstring.should eq "f6"
+    end
+    it "union (Nil | Bool) (false)" do
+      value = (Nil | Bool).from_cbor(false.to_cbor).to_cbor
+      value.hexstring.should eq "f4"
+    end
+  end
+end
+