MariaDB [koha_kohadev]> select borrowernumber,  guarantorid from borrowers where guarantorid is not null;                                                                    +----------------+-------------+
| borrowernumber | guarantorid |
+----------------+-------------+
|              6 |         102 |
|              7 |         104 |
|              8 |         112 |
|             15 |         131 |
|             18 |         160 |
|             21 |         177 |
|             30 |         254 |
|             35 |         287 |
|             36 |         288 |
|             37 |         289 |
|             40 |         320 |
|             42 |         337 |
+----------------+-------------+

MariaDB [koha_kohadev]> select max(borrowernumber) from borrowers;                                                                                                           
+---------------------+
| max(borrowernumber) |
+---------------------+
|                  50 |
+---------------------+

That breaks randomly tests on Jenkins (Koha/Patrons.t)


    #   Failed test 'new_patron_1 should have 0 guarantee'
    #   at t/db_dependent/Koha/Patrons.t line 85.
    #          got: '1'
    #     expected: '0'

    #   Failed test 'new_patron_1 should have 0 guarantee'
    #   at t/db_dependent/Koha/Patrons.t line 88.
    #          got: '1'
    #     expected: '0'

    #   Failed test 'new_patron_1 should have 2 guarantees'
    #   at t/db_dependent/Koha/Patrons.t line 95.
    #          got: '3'
    #     expected: '2'

    #   Failed test 'new_patron_1 should have 2 guarantees'
    #   at t/db_dependent/Koha/Patrons.t line 98.
    #          got: '3'
    #     expected: '2'
    # Looks like you failed 4 tests of 8.

#   Failed test 'guarantees'
#   at t/db_dependent/Koha/Patrons.t line 100.

#   Failed test 'Delete should have deleted the patron'
#   at t/db_dependent/Koha/Patrons.t line 905.
#          got: '51'
#     expected: '52'
# Looks like you failed 2 tests of 22.
[16:26:26] t/db_dependent/Koha/Patrons.t ................................