esphome/tests/components/uart/test.host.yaml

esphome:
  on_boot:
    then:
      - uart.write: 'Hello World'
      - uart.write: [0x00, 0x20, 0x42]

uart:
  - id: uart_uart
    port: "/dev/ttyS0"
    baud_rate: 9600
    data_bits: 8
    parity: EVEN
    stop_bits: 2