EMBEDDED SOFTWARE DEVELOPMENT USING BDD

Itamar Hassin September 2014

THIS TALK COVERS

•Embedded development challenges !

•The case for BDD !

•Simulating the target !

•Accessing the target remotely/in-situ !

•Orchestrating access to multiple targets

EMBEDDED DEVELOPMENT CHALLENGES

•A simulator rarely available or not fully functional !

•Remote device verification !

•Complex state-machines !

•Test coverage often limited to unit testing

THE CASE FOR CUCUMBER

•Direct mapping from user story acceptance criteria

!

•Living documentation, unified view of the product !

•Helps defines ‘done’: Code is tested and validated !

•BDD promotes lean code & emergent design !

•Authored by the team: BAs/QA/Devs

CLOSER TO THE SOURCE

PREMISE FOR AUTOMATIONProgramatically validate that code solves the problem by articulating behaviour in machine-readable form.

CUCUMBER FOR EMBEDDED!

WRITE ONCE, USE THRICE

Feature: Alarm assured to appear in quiet mode !Scenario: Pressure alarm Given device is in quiet mode When pressure sensor is disconnected Then a silent alarm will appear

IMPLEMENT STEPS

Given(/Given device is in quiet mode $/) do @device.set_quiet_mode(1) end

IMPLEMENT A SIMULATOR

class Device def set_quiet_mode(flag) if (flag) mode |= QUIET_MODE else mode &= ~QUIET_MODE end update_driver(mode) end end

VALIDATE UNDER SIMULATOR

Scenario: Pressure alarm Given device is in quiet mode When pressure sensor is disconnected Then a silent alarm will appear !

5 scenarios (5 passed) 26 steps (26 passed) 0m0.052s

WHEN SIMULATION IS NOT ENOUGH

THE “WIRE”

•When your system does not have native support

•When you want a lean, portable implementation

SIMPLIFIED WIRE PROTOCOL

WIRE IMPLEMENTATION BLUEPRINT

•TCP/IP loop managing Cucumber protocol

•Function table for API invocation

•API implementation returning status to Cucumber

HOOKING CUCUMBER TO LISTENER

features/step_definitions/cucumber.wire host: deviceport: 3901

LISTENER TCP/IP LOOP

while(fgets(buff, sizeof(buff), rStream)) { respond_to_cucumber(wStream, buff); }

WIRE HANDLERvoid respond_to_cucumber(FILE* stream, char* msg) { if (MSG_TYPE_IS(msg, "step_matches")) respond_to_step_matches(stream, msg); else if (MSG_TYPE_IS(msg, "invoke")) respond_to_invoke(stream, msg); else if (MSG_TYPE_IS(msg, "begin_scenario")) respond_to_begin(stream, msg); else if (MSG_TYPE_IS(msg, "end_scenario")) respond_to_end(stream, msg); else respond_success(stream); }

FUNCTION TABLE

stepdef_t stepdefs[] = { { "device is in quiet mode”, set_quiet_mode } };

INVOKING API FUNCTIONS

void respond_to_invoke(…) { int id = get_function_id(msg); !

stepdefs[id].callback(arg_val) ? failure(stream) : success(stream); }

TARGET API

int set_quiet_mode(const char *arg) { context->requested_mode = atoi(arg); context->quiet_mode |= context->requested_mode; return(update_driver(context)); }

IMPLEMENTATION STACK

WORKING WITH CUCUMBER•Decide on a strategy (off-board, on-board)

•Get appropriate toolchain (cross compiler, linker)

•Implement and port Wire to target

•Run the feature files

•fail/implement/pass/refactor/repeat

USAGE PATTERNS Off-Board

• Framework on PC • Listener on PC • Proxy API on PC

• Network calls to Target API !

In-Situ • Framework on PC • Listener on Target • API calls on Target

Prog

ress

ion

WORKING AT A SAFE DISTANCE

OFF-BOARDCucumber running on

PC

Wire running on PC

Target API running on

PC

Target

NetworkC-implementation

• + Target untouched

• - All API’s must be exposed; low-fidelity; many moving parts;

UP CLOSE AND PERSONAL

IN-SITUFramework running on

PC

Cucumber-Wire running

on Target

Network C-implementation

Target API

• + high-fidelity, API’s not exposed

• - Server part of codebase

COLLABORATIVE ENVIRONMENT

GATEWAY

!

•Acts as an end-to-end test orchestrator !

•Switchboard events across heterogeneous devices

COLLABORATIVE END-TO-END TESTING

Framework running on

PC

C-implementation

Cucumber-Wire running

on Target

Targets

NativeWire

Collaboration

GATEWAY ARCHITECTURE

SpecFlow

Target B

Proxies

A1

B1

Hardware

Serial

Wire

Target ACucumber

Behave

END-TO-END FEATURES

Feature: Alarm assured to appear in quiet mode !

Scenario: Pressure alarm Given device is in quiet mode When pressure sensor is disconnected Then a silent alarm will appear

GATEWAY STEPS public class QuietModeSteps { SignalSimulator signalSimulator = new SignalSimulator(); MedicalDevice medicalDevice = new MedicalDevice(“192.168.1.1”, 3901); ! [Given(@"device is quiet mode")] public void GivenDeviceIsQuietMode() { NUnit.Framework.Assert.IsTrue(medicalDevice.SetQuietMode()); } ! [When(@“pressure sensor is disconnected")] public void GivenPressureSensorIsDisconnected() { NUnit.Framework.Assert.IsTrue(signalSimulator.SetPressure(off)); } }

GATEWAY PROXIES class MedicalDevice { protected Wire wire; ! public MedicalDevice(string ipAddress, int port) { myAddress = ipAddress; wire = new Wire(myAddress, port); wire.Open(); } ! public bool SetQuietMode() { wire.Send("[\"step_matches\",{\"name_to_match\":\"set quiet mode on\"}]\n"); wire.Send("[\"invoke\",{\"id\":\"7\",\"args\":[\"on\"]}]\n"); return(wire.Ack()); } }

EMULATING WIRE public class Wire { public int Open() { client = new TcpClient(myAddress, myPort); stream = client.GetStream(); return(Send(“[\”begin_scenario\"]\n")); } ! public int Close() { stream = client.GetStream(); Send("[\"end_scenario\"]\n"); return(client.Close()); } }

SpecFlow

Wire

Proxies

A1

Target

TCP

Given … quiet mode

Wire

int SetQuietMode(“on”) {}

Match: “set quiet\’(on|off)’\”

Invoke: idx:0, params: “on”

SPECFLOW TO WIRE

int set_quiet(char* state){}A

Exists in proxy? Write wrappers

Exists in Wire?

No

NoYes

Function table entry

Yes

Use in feature/step files

API Exists? No Implement API

Yes

MAINTENANCE CONSIDERATIONS

•Security - Anyone can connect to Wire!

•Regulation may not allow non-application code on a production system

Shut down the wire thread in production

COMPLIANCE CONSIDERATIONS

LESSONS LEARNED

Threading

Dual VocabularyThreads & Target Architecture

REFERENCES•Specification by example

•The Cucumber Book

•Cucumber Recipes

@history_pics/@historyinpicsJim Reese#Wikipedia

National Library of Australia

Photo Credits:

•SpecFlow

THANK YOU!@itababy

www.in-context.com