tests/glibmm_ustring_format: Fix non-English langs

>>>
when I tested it, the glibmm_ustring_format test failed. It failed
because my chosen language in Ubuntu is Swedish. The expected "42.00"
became "42,00". The decimal delimiter is a comma in most European
languages. English is an exception.
>>>

https://gitlab.gnome.org/GNOME/glibmm/merge_requests/4#note_352960

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/glibmm_ustring_format/main.cc b/tests/glibmm_ustring_format/main.cc
index 76a3efab..62a39ba6 100644
--- a/tests/glibmm_ustring_format/main.cc
+++ b/tests/glibmm_ustring_format/main.cc
@@ -6,6 +6,10 @@
 int
 main(int, char**)
 {
+  // Don't use the user's preferred locale. The decimal delimiter may be ','
+  // instead of the expected '.'.
+  Glib::set_init_to_users_preferred_locale(false);
+
   Glib::init();
 
   char carr[10] = "Užduotys";