Add basic test for spawning userscripts

tests/integration/data/userscripts/open_current_url

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+echo "open -t $QUTE_URL" >> "$QUTE_FIFO"

tests/integration/features/spawn.feature

@@ -15,3 +15,10 @@ Feature: :spawn
     Scenario: Running :spawn with url variable
         When I run :spawn echo {url}
         Then "Executing echo with args ['about:blank'], userscript=False" should be logged
+
+    Scenario: Running :spawn with userscript
+        When I run :spawn --userscript open_current_url
+        And I wait until about:blank is loaded
+        Then the following tabs should be open:
+            - about:blank
+            - about:blank (active)