diff --git a/spec/rscons/util_spec.rb b/spec/rscons/util_spec.rb
new file mode 100644
index 0000000..dc1190b
--- /dev/null
+++ b/spec/rscons/util_spec.rb
@@ -0,0 +1,31 @@
+module Rscons
+  describe Util do
+
+    describe ".make_relative_path" do
+      context "when passed a relative path" do
+        it "returns the path itself" do
+          expect(Util.make_relative_path("foo/bar")).to eq "foo/bar"
+        end
+      end
+
+      context "when passed an absolute path" do
+        before(:each) do
+          expect(Rscons).to receive(:absolute_path?).and_return(true)
+        end
+
+        context "on Windows" do
+          it "returns a relative path corresponding to an absolute one" do
+            expect(Util.make_relative_path("D:/foo/bar")).to eq "_D/foo/bar"
+          end
+        end
+
+        context "on POSIX" do
+          it "returns a relative path corresponding to an absolute one" do
+            expect(Util.make_relative_path("/foo/bar")).to eq "_/foo/bar"
+          end
+        end
+      end
+    end
+
+  end
+end