esphome/tests/integration/fixtures/scheduler_simultaneous_callbacks.yaml

esphome:
  name: sched-simul-callbacks-test

external_components:
  - source:
      type: local
      path: EXTERNAL_COMPONENT_PATH
    components: [scheduler_simultaneous_callbacks_component]

host:

logger:
  level: INFO

scheduler_simultaneous_callbacks_component:
  id: simultaneous_callbacks

api:
  services:
    - service: run_simultaneous_callbacks_test
      then:
        - lambda: |-
            id(simultaneous_callbacks)->run_simultaneous_callbacks_test();