diff --git a/fetch-latest-releases.lua b/fetch-latest-releases.lua
index 3f2104d..ad019c5 100755
--- a/fetch-latest-releases.lua
+++ b/fetch-latest-releases.lua
@@ -98,6 +98,13 @@ function get_releases(branch, destdir)
 	return t
 end
 
+-- return functions as module for unit testing
+if not string.match(arg[0], "fetch%-latest%-releases") then
+	return {
+		fatal = fatal,
+	}
+end
+
 local branch = arg[1] or "edge"
 local destdir = arg[2] or "out"
 
diff --git a/tests/fetch-latest-releases_spec.lua b/tests/fetch-latest-releases_spec.lua
new file mode 100644
index 0000000..0842b47
--- /dev/null
+++ b/tests/fetch-latest-releases_spec.lua
@@ -0,0 +1,18 @@
+describe("test fetch-latest-releases functions", function()
+	local f
+	setup(function()
+		f = require("fetch-latest-releases")
+	end)
+
+	teardown(function()
+		f = nil
+	end)
+
+	describe("test fatal", function()
+		it("should call os.exit", function()
+			stub(os, "exit")
+			f.fatal("hello")
+			assert.stub(os.exit).was_called_with(1)
+		end)
+	end)
+end)