Testing drivers

There are three kind of drivers
  • Streaming IO (TCP, SSH, UDP, Multicast, ect)
  • HTTP Client
  • Logic
From a driver code structure standpoint there is no difference between these types.
  • The same driver can be used over a TCP, UDP or SSH transport.
  • All drivers support HTTP methods if a URI endpoint is defined.
  • If a driver is associated with a System then it has access to logic helpers
During a test, the loaded module is loaded with a TCP transport, HTTP enabled and logic module capabilities. This allows for testing the full capabilities of any driver.
The driver is launched as it would be in production.


Specs have access to Crystal lang spec expectations. This allows you to confirm expectations.
variable = 34
variable.should eq(34)
There is a good overview on how to use expectations on the crystal lang docs site


Expectations are primarily there to test the state of the module.
  • You can access state via the status helper: status[:state_name]
  • Then you can check it an expected value: status[:state_name].should eq(14)

Testing Streaming IO

The following functions are available for testing streaming IO:
  • transmit(data) -> transmits the object to the module over the streaming IO interface
  • responds(data) -> alias for transmit
  • should_send(data, timeout = 500.milliseconds) -> expects the module to respond with the data provided
  • expect_send(timeout = 500.milliseconds) -> returns the next Bytes sent by the module (useful if the data sent is not deterministic, i.e. has a time stamp)
A common test case is to ensure that module state updates as expected after transmitting some data to it:
# transmit some data
# check that the state updated as expected
status[:area2001].should eq(1)

Testing HTTP requests

The test suite emulates a HTTP server so you can inspect HTTP requests and send canned responses to the module.
expect_http_request do |request, response|
io = request.body
if io
data = io.gets_to_end
request = JSON.parse(data)
if request["message"] == "hello steve"
response.status_code = 202
response.status_code = 401
raise "expected request to include dialing details #{request.inspect}"
# check that the state updated as expected
status[:area2001].should eq(1)
Use expect_http_request to access an expected request coming from the module.
  • when the block completes, the response is sent to the module
  • you can see request object details here:
  • you can see response object details here:

Executing functions

This allows you to request actions be performed in the module via the standard public interface.
  • exec(:function_name, argument_name: argument_value) -> response a response future (async return value)
  • You should send and responds(data) before inspecting the response.get
# Execute a command
response = exec(:scene?, area: 1)
# Check that the command causes the module to send some data
# Respond to that command
# Check if the functions return value is expected
response.get.should eq(2)
# Check if the module state is correct
status[:area1].should eq(2)

Testing Logic

Logic modules typically expect a system to contain some drivers which the logic modules interacts with.
# define mock versions of the drivers it will interact with
class Display < DriverSpecs::MockDriver
include Interface::Powerable
include Interface::Muteable
enum Inputs
include PlaceOS::Driver::Interface::InputSelection(Inputs)
# Configure initial state in on_load
def on_load
self[:power] = false
self[:input] = Inputs::HDMI
# implement the abstract methods required by the interfaces
def power(state : Bool)
self[:power] = state
def switch_to(input : Inputs)
self[:input] = input
def mute(
state : Bool = true,
index : Int32 | String = 0,
layer : MuteLayer = MuteLayer::AudioVideo
self[:mute] = state
self[:mute0] = state
Then you can define the system configuration, you can also change the system configuration throughout your spec to test different configurations.
DriverSpecs.mock_driver "Place::LogicExample" do
# Where `{Display, Display}` is referencing the `MockDriver` class defined above
# and `Display:` is the friendly name
# so this system would have `Display_1`, `Display_2`, `Switcher_1`
Display: {Display, Display},
Switcher: {Switcher},
# ...
Along with the physical system configuration you can test different setting configurations. Settings can also be changed throughout the life cycle of your spec.
DriverSpecs.mock_driver "Place::LogicExample" do
name: "Meeting Room 1",
map_id: "1.03"
An action you perform on your driver might be expected to update state in the mock devices. You can access this state via the system helper
DriverSpecs.mock_driver "Place::LogicExample" do
# execute a function in your logic module
exec(:power, true)
# Check that the expected state has updated in you mock device
system(:Display_1)[:power].should eq(true)
# manually execute a function on a mock device
# need to cast the mock to the appropriate class
system(:Display_1).as(Display).power false
All status queried in this manner is returned as a JSON::Any object