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Version: 9.x.x

Mock Bindings

new MockBinding(options: OpenOptions)

Testing is an important feature of any library. To aid in our own tests, we've developed a MockBinding, a fake hardware binding that doesn't actually need any hardware to run. This class passes all of the same tests as our hardware based bindings and provides a few additional test related interfaces.

To simulate incoming data on a mock port, use port.binding.emitData.


const SerialPort = require('@serialport/stream')
const MockBinding = require('@serialport/binding-mock')
const Readline = require('@serialport/parser-readline')

SerialPort.Binding = MockBinding

// Create a port and enable the echo and recording.
MockBinding.createPort('/dev/ROBOT', { echo: true, record: true })
const port = new SerialPort('/dev/ROBOT')

/* Add some action for incoming data. For example,
** print each incoming line in uppercase */
const parser = new Readline()
port.pipe(parser).on('data', line => {

// wait for port to open...
port.on('open', () => {
// ...then test by simulating incoming data
port.binding.emitData("Hello, world!\n")

/* Expected output:
const AbstractBinding = require('@serialport/binding-abstract')
const debug = require('debug')('serialport/binding-mock')

let ports = {}
let serialNumber = 0

function resolveNextTick(value) {
return new Promise(resolve => process.nextTick(() => resolve(value)))

* Mock bindings for pretend serialport access
class MockBinding extends AbstractBinding {
// if record is true this buffer will have all data that has been written to this port
readonly recording: Buffer

// the buffer of the latest written data
readonly lastWrite: null | Buffer

// Create a mock port
static createPort(path: string, opt: { echo?: boolean, record?: boolean, readyData?: Buffer}): void

// Reset available mock ports
static reset(): void

// list mock ports
static list(): Promise<PortInfo[]>

// Emit data on a mock port
emitData(data: Buffer | string | number[])

// Standard bindings interface
open(path: string, opt: OpenOpts): Promise<void>
close(): Promise<void>
read(buffer: Buffer, offset: number, length: number): Promise<Buffer>
write(buffer: Buffer): Promise<void>
update(options: { baudRate: number }): Promise<void>
set(options): Promise<void>
get(): Promise<Flags>
getBaudRate(): Promise<number>
flush(): Promise<void>
drain(): Promise<void>