Properly handle promise in superspawn test
diff --git a/spec/superspawn.spec.js b/spec/superspawn.spec.js
index 2b354b1..95056dc 100644
--- a/spec/superspawn.spec.js
+++ b/spec/superspawn.spec.js
@@ -98,7 +98,7 @@
                 pending('test should only run on windows');
             }
 
-            superspawn.spawn(TEST_SCRIPT, TEST_ARGS).then(output => {
+            return superspawn.spawn(TEST_SCRIPT, TEST_ARGS).then(output => {
                 expect(output.split(/\r?\n/)).toEqual(TEST_ARGS);
             });
         });