+
+test_begin_subtest 'at most 1 thread-id per xapian document'
+db=${MAIL_DIR}/.notmuch/xapian
+for doc in $(xapian-delve -1 -t '' "$db" | grep '^[1-9]'); do
+ xapian-delve -1 -r "$doc" "$db" | grep -c '^G'
+done > OUTPUT.raw
+sort -u < OUTPUT.raw > OUTPUT
+cat <<EOF > EXPECTED
+0
+1
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+