diff --git a/src/lib/__tests__/cx.spec.js b/src/lib/__tests__/cx.spec.js
new file mode 100644
index 00000000..1127b04b
--- /dev/null
+++ b/src/lib/__tests__/cx.spec.js
@@ -0,0 +1,10 @@
+import { cx } from '../cx';
+
+test('cx', () => {
+  expect(cx(null)).toEqual('');
+  expect(cx(undefined)).toEqual('');
+  expect(cx('--')).toEqual('bx--');
+  expect(cx('--', null)).toEqual('bx--');
+  expect(cx(0, undefined, '--', null, 1)).toEqual('bx--');
+  expect(cx(1 && '1', 0 && '0')).toEqual('1');
+});