Set an AutocompleteField on FullFeaturedSnippet so TestFilterSetClassSearch works correctly

CHANGELOG.txt

@@ -4,7 +4,7 @@ Changelog
 5.2 (xx.xx.xxxx) - IN DEVELOPMENT
 ~~~~~~~~~~~~~~~~
 
- * ...
+ * Maintenance: Fix snippet search test to work on non-fallback database backends (Matt Westcott)
 
 
 5.1 (xx.xx.xxxx) - IN DEVELOPMENT

docs/releases/5.2.md

@@ -26,7 +26,7 @@ depth: 1
 
 ### Maintenance
 
- * ...
+ * Fix snippet search test to work on non-fallback database backends (Matt Westcott)
 
 
 ## Upgrade considerations

wagtail/test/testapp/models.py

@@ -1121,6 +1121,7 @@ class FullFeaturedSnippet(
 
     search_fields = [
         index.SearchField("text"),
+        index.AutocompleteField("text"),
         index.FilterField("text"),
         index.FilterField("country_code"),
     ]