AFTER INSERT trigger INSERT into another table-B are ignoring Table-B constraints

This is a trigger related question.

Table, test_part_details_all_mcm_init  has a trigger, tr_test_part_details_all_mcm_init.

CREATE TRIGGER tr_test_part_details_all_mcm_init

    AFTER INSERT

    ON bx.test_part_details_all_mcm_init

    FOR EACH ROW

    EXECUTE FUNCTION bx.tr_fn_test_part_details_all_mcm_init();

Function, bx.tr_fn_test_part_details_all_mcm_init() INSERTs a row into another table, bx.test_part_details_all_mcm_mid

Table, bx.test_part_details_all_mcm_mid has a constraint,

CONSTRAINT cons_unique_for_concatenated_view UNIQUE (start_time_numeric, stop_time_numeric, test_action, part_type, fixture_id, run_id, auxid1_build_id, auxid2_asic_id, serial_number, part_pf)

When I INSERT a data into the table Table, test_part_details_all_mcm_init  , trigger is not checking CONSTRAINT cons_unique_for_concatenated_view while INSERTing the data in bx.test_part_details_all_mcm_mid. I am expecting that anything violating the constraint cons_unique_for_concatenated_view will throw an error. Instead of that it is allowing to INSERT the data.

What is that I am missing here?

Thanks,

Sarwar