Add testcase for Gtk.ComboBox

Signed-off-by: Manuel Quiñones <manuq@laptop.org>

tests/graphics/combobox.py

@@ -0,0 +1,24 @@
+from gi.repository import Gtk
+
+import common
+
+
+test = common.Test()
+test.show()
+
+# test Gtk.ComboBox:
+
+store = Gtk.ListStore(int, str)
+for i in range(100):
+    description = "combo test entry %d" % i
+    store.append([i, description])
+
+combobox = Gtk.ComboBox(model=store)
+cell = Gtk.CellRendererText()
+combobox.pack_start(cell, True)
+combobox.add_attribute(cell, 'text', 1)
+test.pack_start(combobox, True, True, 0)
+combobox.show()
+
+if __name__ == '__main__':
+    common.main(test)