Strengthen GUI tests

Author: GuillaumeGomez

gui-tests/sidebar.goml

@@ -9,6 +9,7 @@ assert-position: (".rustdoc .sidebar", {"y": |topbar_height|, "x": 0})
 
 // We check the same in "mobile mode".
 set-window-size: (600, 1000)
+wait-for-css-false: (".rustdoc .mobile-topbar", {"display": "none"})
 assert-position: (".rustdoc .mobile-topbar", {"y": |topbar_height|, "x": 0})
 // We check when the sidebar is shown now.
 click: ".rustdoc .mobile-topbar .sidebar-menu-toggle"

gui-tests/theme.goml

@@ -6,7 +6,7 @@
 // the crate page we control the whole page
 
 go-to: |DOC_PATH| + "/sysinfo"
-set-local-storage: { "rustdoc-theme": null }
+set-local-storage: { "rustdoc-theme": "light" }
 wait-for-css: (".nav-container", { "background-color": "rgb(255, 255, 255)" })
 go-to: |DOC_PATH| + "/crate/sysinfo"
 wait-for-css: ("body", { "background-color": "rgb(255, 255, 255)" })