jstests/libs/test_background_ops.js redefines the startParallelShell() function built into the mongo shell. The definition in jstests/libs/test_background_ops.js won't throw a JavaScript exception even if the parallel shell exits with a non-zero return code.

The following tests appear to call one of startParallelShell(), startParallelOps(), or moveChunkParallel() and either directly or indirectly end up loading jstests/libs/test_background_ops.js:

• jstests/change_streams/change_streams_lookup_preimage_with_chunk_migration.js
• jstests/multiVersion/genericBinVersion/minor_version_upgrade_replset.js
• jstests/multiVersion/genericSetFCVUsage/3_upgrade_replset.js
• jstests/multiVersion/genericSetFCVUsage/downgrade_replset.js
• jstests/noPassthrough/create_indexes_in_txn_errors_if_already_in_progress.js
• jstests/noPassthroughWithMongod/create_indexes_waits_for_already_in_progress.js
• jstests/noPassthroughWithMongod/create_new_indexes_with_conflict.js
• jstests/replsets/ddl_op_behind_transaction_fails_in_shutdown.js
• jstests/replsets/reconfig_avoids_diverging_configs.js
• jstests/sharding/bump_transaction_prevents_extra_deletion_task_write.js
• jstests/sharding/index_commands_shard_targeting.js
• jstests/sharding/migration_critical_section_concurrency.js
• jstests/sharding/migration_ignore_interrupts_1.js
• jstests/sharding/migration_ignore_interrupts_2.js
• jstests/sharding/migration_move_chunk_after_receive.js
• jstests/sharding/migration_recovers_unfinished_migrations.js
• jstests/sharding/migration_server_status.js
• jstests/sharding/migration_sets_fromMigrate_flag.js
• jstests/sharding/migration_waits_for_majority_commit.js
• jstests/sharding/migration_with_source_ops.js
• jstests/sharding/move_chunk_remove_shard.js
• jstests/sharding/move_chunk_update_shard_key_in_retryable_write.js
• jstests/sharding/movechunk_parallel.js
• jstests/sharding/prepare_transaction_then_migrate.js
• jstests/sharding/recover_multiple_migrations_on_stepup.js
• jstests/sharding/safe_secondary_reads_causal_consistency.js
• jstests/sharding/txn_writes_during_movechunk.js
• jstests/sharding/unfinished_migration_server_status.js
• jstests/sharding/write_transactions_during_migration.js