# TTY0TTY
[](https://api.reuse.software/info/github.com/jjcarstens/tty0tty)
Elixir port for [`tty0tty` null modem emulator](https://github.com/freemed/tty0tty)
## Use
This library is almost exclusively for testing purposes. `tty0tty` creates 2
pseudo-ttys that are connected together allowing you to run unit tests which
use serial ports (like [`Circuits.UART`](https://github.com/elixir-circuits/circuits_uart))
without the need for external hardware of adapters.
```elixir
defmodule SerialTest do
use ExUnit.Case, async: true
test "can open a serial port" do
{:ok, uart} = Circuits.UART.start_link()
port_name = "/tmp/dummy1"
# Open serial port before use
{:ok, _port_sup} = TTY0TTY.open(port_name)
assert :ok = Cicuits.UART.open(uart, port_name)
end
end
```
Under the hood, `TTY0TTY.open/2` opens 2 devices (`<port_name>`, and
`<port_name>-twin`) and connects their TX <-> RX to emulate the serial
connection. This allows you to also verifying reading serial data by sending
data to the connected twin port:
```elixir
defmodule SerialTest do
use ExUnit.Case, async: true
test "can read a serial port" do
{:ok, uart} = Circuits.UART.start_link()
port_name = "/tmp/dummy1"
# Open serial port before use
{:ok, _port_sup} = TTY0TTY.open(port_name)
assert :ok = Cicuits.UART.open(uart, port_name)
File.write!([port_name, "-twin"], "howdy!")
assert_receive {:circuits_uart, ^port_name, "howdy!"}
end
end
```
