Function setTxPending

setTxPending(
    func: (
        msg: CanMessage,
    ) =>
        | undefined
        | Buffer<ArrayBufferLike>
        | Promise<undefined | Buffer<ArrayBufferLike>>,
): void
Sets a "pending transmit" handler for CAN messages used by jobs/diagnostics.

Allows test frameworks or diagnostic jobs to temporarily override outgoing CAN message transmission. The provided callback is invoked before each CAN transmit.
Parameters
- func: (
      msg: CanMessage,
  ) =>
      | undefined
      | Buffer<ArrayBufferLike>
      | Promise<undefined | Buffer<ArrayBufferLike>>
  Callback taking a CanMessage and returning:
  
  a Buffer (to override and send as transmit data),
  
  msg.data (to send the message unchanged),
  
  undefined (to suppress/disable this transmission),
  
  or a Promise resolving to any of the above.
Returns void
Example
```
setTxPending(async (msg) => {
  // E2E test: intercept message with ID 0x200
  if (msg.id === 0x200) {
    // Replace transmit data for E2E injection
    return Buffer.from([0xE2, 0xE2, 0xCA, 0xT1]);
  }
  // Block this transmission (do not send)
  return undefined;
});
```
Example
```
setTxPending((msg) => {
  // Only log, transmit as usual
  console.log("CAN TX:", msg);
  return msg.data; // will not alter data
});
```