The Physics of Debug Later Programming (DLP)

Test Driven Development for Embedded C

Presented by James Grenning at Agile China 2010 twitter: jwgrenning
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Td

Tnd

T x Time

Mistake made (bug injection)

Bug discovery Bug found Bug xed

As Td increases, Tfind increases dramatically Tfix is usually short, but can increase with Td
http://pragprog.com/titles/jgade/
www.renaissancesoftware.net james@renaissancesoftware.net

Presented at Agile China October 14, 2010 Test Driven Development

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Copyright 2008-2010 James W. Grenning All Rights Reserved.

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

The Physics of Test Driven Development

T d Tnd T x Time Mistake Mistake xed made Mistake Root cause found discovery

TDD Micro Cycle

Write a test Watch it fail Make it pass Refactor (clean up any mess) Repeat until done

When Td approaches zero, Tfind approaches zero In many cases, bugs are not around long enough to be considered bugs. See: http://www.renaissancesoftware.net/blog/archives/16
Copyright 2008-2010 James W. Grenning All Rights Reserved. www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

TDD State Machine in C/C++

Start

Test Driving a Circular Buffer (FIFO)

Choose a test No more tests All tests pass

Write the test

Compilation error

23

66

12

99

16

90

99

Compiles Clean
Refactor (Make it right) DONE! All tests pass Link error Make the test compile Compilation error

Out-Index

In-Index

Programming error

Make the test pass

New test fails

Make the test link

Link error

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Create a Test-List (avoid analysis paralysis)

Circular Buffer Tests Initially Empty Transition to empty Transition to Full Transition from Full Put-Get FIFO Put to full Get from empty Filled but not wrapped around Wrap around

Set up a Test Fixture

TEST_GROUP(CircularBuffer) { CircularBuffer* buffer; void setup() { buffer = CircularBuffer_Create(); } void teardown() { CircularBuffer_Destroy(buffer); } }; TEST(CircularBuffer, TestName) { }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Make a bare Skeleton of the Production Code

#ifndef D_CircularBuffer_H #define D_CircularBuffer_H typedef struct CircularBuffer CircularBuffer; CircularBuffer * CircularBuffer_Create(int capacity); void CircularBuffer_Destroy(CircularBuffer *); #endif // D_CircularBuffer_H

Make a bare Skeleton of the Production Code

#include "CircularBuffer.h" #include <stdlib.h> struct CircularBuffer { int dummy; } ; CircularBuffer* CircularBuffer_Create() { CircularBuffer* self = calloc(capacity, sizeof(CircularBuffer)); return self; } void CircularBuffer_Destroy(CircularBuffer* self) { free(self); }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Choose a Test
Start

Which Test?

Choose a test No more tests All tests pass

Write the test

Compilation error

Compiles Clean
Refactor (Make it right) DONE! All tests pass Link error Make the test compile Compilation error

Out-Index

In-Index

41
New test fails Make the test link Link error

59

14

33

31

Programming error

Make the test pass

In-Index

Out-Index

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Production Code is Grown One Test at a Time

Write a Test
Start

Choose a test No more tests

Write the test

Code without new feature

Code with new tested feature

DONE!

All tests pass

Compilation error

Compiles Clean
Refactor (Make it right) Make the test compile Link error Compilation error

All tests pass

Programming error

Make the test pass

New test fails

Make the test link

Link error

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Start with a Test That is Easy to Get to Pass -- Designing the Interface
TEST_GROUP(CircularBuffer) { CircularBuffer* buffer; void setup() { buffer = CircularBuffer_Create(); } void teardown() { CircularBuffer_Destroy(buffer); } }; TEST(CircularBuffer, ShouldBeEmptyAfterCreate) {
CHECK(CircularBuffer_IsEmpty(buffer));
Programming error

Make the Test Compile

Start

Choose a test No more tests All tests pass

Write the test

Compilation error

Compiles Clean
Refactor (Make it right) DONE! All tests pass Link error Make the test compile Compilation error

Make the test pass

New test fails

Make the test link

Link error

}
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Make the Test Compile

#ifndef D_CircularBuffer_H #define D_CircularBuffer_H typedef struct CircularBuffer CircularBuffer;

Make the Test Link

Start

Choose a test

Write the test

CircularBuffer * CircularBuffer_Create(int capacity); void CircularBuffer_Destroy(CircularBuffer *); int CircularBuffer_IsEmpty(CircularBuffer *); #endif // D_CircularBuffer_H

No more tests All tests pass Compilation error

Compiles Clean
Refactor (Make it right) DONE! All tests pass Link error Make the test compile Compilation error

Programming error

Make the test pass

New test fails

Make the test link

Link error

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Make the Test Link and Intentionally Fail

#include "CircularBuffer.h" #include <stdlib.h> struct CircularBuffer { int dummy; } ; ... not all code shown ... int CircularBuffer_IsEmpty(CircularBuffer* self) { return 0; }

Watch it Fail
CircularBufferTest.cpp:48: error: Failure in TEST(CircularBuffer, EmptyAfterCreation) CHECK(CircularBuffer_IsEmpty(buffer)) failed

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Make the Test Pass

Start

Write no More Code than is Necessary to Pass the Current Test

Hard code behavior or partial implementations are OK and often preferred.

Choose a test No more tests All tests pass

Write the test

Compilation error

Compiles Clean
Refactor (Make it right) DONE! All tests pass Link error Make the test compile Compilation error

Programming error

Make the test pass

New test fails

Make the test link

Link error

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Make the Test Pass

#include "CircularBuffer.h" #include <stdlib.h> struct CircularBuffer { int dummy; } ; ... not all code shown ... int CircularBuffer_IsEmpty(CircularBuffer* self) { return 1; }

Repeat until You Run Out of Tests

The first tests drive the interface definition Later tests complete the behavior You will think of more tests as you go
Write the new test or Add it to the test list

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Tests are FIRST

Thank you: Tim Ottinger

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Fast Independent Repeatable Self-validating Timely

Presented at Agile China October 14, 2010 Test Driven Development
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Adaptation for Embedded Software

What is scarce during embedded development?

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Hardware is Scarce!
It does not exist. It is being used by someone else.

Hardware is Scarce!
It does not exist. It is being used by someone else.

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Hardware Has Bugs of its Own

bool BlindsScheduler::DoesLightRespondToday (TimeService::Day reactionDay) { int today = timeService->GetDay(); if (reactionDay == TimeService::EVERYDAY) return true; if (reactionDay == today) return true; if (reactionDay == TimeService::WEEKEND && (TimeService::SATURDAY == today || TimeService::SUNDAY == today)) return true; if (reactionDay == TimeService::WEEKDAY && today >= TimeService::MONDAY && today <= TimeService::FRIDAY) return true; return false; } void BlindsScheduler::CheckEvent(ScheduledBlindsEvent* blindsEvent) { if (blindsEvent->extraRandomEventPreventer > 0) { blindsEvent->extraRandomEventPreventer--; return; } if (!DoesLightRespondToday(blindsEvent->day)) return; if (timeService->GetMinute() != blindsEvent->minute + blindsEvent->randomMinutes) return; switch (blindsEvent->blindsType) { HorizontalBlinds* theBlinds; case Horizontal: switch (blindsEvent->operation) { case Raise:

Tests Must be Fast and We Can Run Them NOW

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Use Your Development System for a Test Bed

Multi-targeted code. Must beware of hardware and OS dependencies. Object Oriented approach to Dependency Management. Avoid inefficiencies
Waiting for hardware. Waiting for restart. Waiting for downloads. Waiting for long compiles. Debugging on the target.
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

But There are Risks with Development System Tests

Architecture differences
Word size Big-endian Little-endian Alignment

Compiler differences Library differences Execution differences

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

TDD Adaptation for Embedded Development

Stage 1 Stage 2 Stage 3 Stage 4 Stage 5

TDD Adaptation for Embedded Development

Stage 1 Stage 2 Stage 3 Run Tests in the Eval Hardware or Simulator Stage 4 Stage 5

Write a Test Make it Pass Refactor

Compile for Target Processor

Run Tests in the Eval Hardware

Run Tests in Target Hardware

Acceptance Tests

Write a Test Make it Pass Refactor

Compile for Target Processor

Run Tests in Target Hardware

Run Manual Tests in Target

More Frequent

More Frequent

Less Frequent

Less Frequent

See : http://renaissancesoftware.net/files/articles/ProgressBeforeHardware.pdf
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Automate Stages 2-5

Source Code Repository

Continuous Integration Server

Test Management System

TDD and the Code in the Middle

(most of the code!)

Eval/Reference System Developer Workstation Target System Simulator

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

What about Code in the Middle

Testing a Module in the Middle

The test case takes the role of the client

The Module under test is tested independent of other modules

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

The servers might need to be stubbed out

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

A Module with Collaborators

Every minute, the RTOS wakes up the Light Scheduler. If it is time for one of the lights to be controlled, the LightController is told to turn on/off the light.
Admin Console Light Scheduler +addSchedule() +removeSchedule() +wakeUp()
<<anonymous callback>>

Program to Interfaces
Separate interface and implementation as separate entities. This design has good separation of responsibilities
Admin Console Light Scheduler +addSchedule() +removeSchedule() +wakeUp()
<<anonymous callback>>

Light Controller + on(id) + off(id)

Time Service + getDay() + getTimeOfDay() + setPeriodicAlarm() RTOS

Light Controller + on(id) + off(id)

<<interface>>

Time Service + getDay() + getTimeOfDay() + setPeriodicAlarm()

<<implements>>

<<interface>>

Hardware

<<implements>>

Real Light Controller

Real Time Service

Hardware
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

RTOS
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Presented at Agile China October 14, 2010 Test Driven Development

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Monday, October 18, 2010

Monday, October 18, 2010

Testing a Module with Collaborators

Use the real collaborators if you can. Use fakes when you must.
Light Scheduler Test Light Scheduler +addSchedule() +removeSchedule() +wakeUp()

Testing the Scheduler

TEST(LightScheduler, ScheduleOnTodayNotTimeYet) { LightScheduler_ScheduleTurnOn(3, EVERYDAY, 1000); FakeTimeSource_SetMinute(999); LightScheduler_Wakeup(); LONGS_EQUAL(LIGHT_NA, FakeLightController_getState(3));

Light Controller + on(id) + off(id)

<<interface>>

Time Service + getDay() + getTimeOfDay() + setPeriodicAlarm()

<<implements>>

<<interface>>

} TEST(LightScheduler, ScheduleOnTodayItsTime) { LightScheduler_ScheduleTurnOn(3, EVERYDAY, 1000); FakeTimeSource_SetMinute(1000); LightScheduler_Wakeup(); LONGS_EQUAL(LIGHT_ON, FakeLightController_getState(3)); }

<<implements>>

Light Controller Spy

Fake Time Service

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Light Controller Interface

#ifndef D_LightController_H #define D_LightController_H enum { MAX_LIGHTS = 32 }; void void void void LightController_Create(void); LightController_Destroy(); LightController_On(int id); LightController_Off(int id); // D_LightController_H

Fake Light Controller Interface

#ifndef D_FakeLightController_H #define D_FakeLightController_H #include "LightController.h" typedef enum { NO_ID = -1, UNKNOWN_STATE = -1, LIGHT_OFF = 0, LIGHT_ON = 1} LightState; int FakeLightController_getLastId(void); int FakeLightController_getLastState(void); int FakeLightController_getState(int id); #endif // D_FakeLightController_H

#endif

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Fake Light Controller Implementation

#include "FakeLightController.h" #include "memory.h" static int lastId; static int lastLevel; void LightController_Create(void) { lastId = NO_ID; lastLevel = UNKNOWN_STATE; } void LightController_Destroy() { }

Fake Light Controller Implementation

int FakeLightController_getLastId(void) { return lastId; } int FakeLightController_getLastState(void) { return lastLevel; } void LightController_On(int id) { lastId = id; lastLevel = LIGHT_ON; } void LightController_Off(int id) { lastId = id; lastLevel = LIGHT_OFF; }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Testing the Scheduler

TEST(LightScheduler, NoScheduleNothingHappens) { LightScheduler_Wakeup(); LONGS_EQUAL(NO_ID, FakeLightController_getLastId()); LONGS_EQUAL(UNKNOWN_STATE, FakeLightController_getLastState()); } TEST(LightScheduler, ScheduleOnTodayNotTimeYet) { LightScheduler_ScheduleTurnOn(3, EVERYDAY, 1200); FakeTimeService_SetMinute(1199); LightScheduler_Wakeup(); LONGS_EQUAL(NO_ID, FakeLightController_getLastId()); LONGS_EQUAL(UNKNOWN_STATE, FakeLightController_getLastState()); }

Testing the Scheduler

TEST(LightScheduler, ScheduleWeekdayItsSunday) { LightScheduler_ScheduleTurnOn(3, EVERYDAY, 1200); FakeTimeService_SetDay(SUNDAY); FakeTimeService_SetMinute(1200); LightScheduler_Wakeup(); LONGS_EQUAL(3, FakeLightController_getLastId()); LONGS_EQUAL(LIGHT_ON, FakeLightController_getLastState()); }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

When must you use fakes?

When the Code under test cannot be fully tested with the real collaborators. Examples:
When manual verification is needed (Printed output, LEDs) When the results change (Time, random events) When failures need to be simulated (Network down) When hardware is involved (LEDs, USB, Sensors, Motors, IO pins, Flash...) Operating system calls (RTOS)

Breaking Dependencies with Function Pointers

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Loosening Compile-Time and Run-Time Dependencies

Problem: an existing C function needs to be stubbed out for some tests...
//From the .h file ... int RandomMinuteGenerator_Get(); ...

Convert Direct Dependency to Function Pointer

Modify the function declaration in the header file
Add extern Add (*)

//From the .c file ... int RandomMinuteGenerator_Get() { ...the implementation... } ...

//From the .h file ... extern void (*RandomMinuteGenerator_Get)(); ...

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Convert Direct Dependency to Function Pointer

Modify the function definition in the .c file
Change function name by appending _impl Hide the _impl by making it static

No Changes are Needed to Callers of the Function Pointer

Calling code does not change. No pointer dereferencing is needed
//from some production code... ... RandomMinuteGenerator_Get(); ...

Add defining instance of the function pointer and initialize the pointer with the the _impl
//From the .c file ... static int RandomMinuteGenerator_Get_impl() { ...the implementation... } int (*RandomMinuteGenerator_Get)() = RandomMinuteGenerator_Get_impl;

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Monday, October 18, 2010

Runtime Substitution Test setup and teardown

Override the function by assigning the test version of the function during setup Dont forget to restore the original
void setup() { RandomMinuteGenerator_Get = RandomMinuteGenerator_Get_fake; } void teardown() { RandomMinuteGenerator_Get = RandomMinuteGenerator_Get_impl; }

Use CppUTests UT_PTR_SET

void setup() { UT_PTR_SET(RandomMinuteGenerator_Get, RandomMinuteGenerator_Get_fake); } void teardown() { }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Monday, October 18, 2010

Monday, October 18, 2010

Message Flow for Flash Memory Block Erase with Error

FlashDriver FlashDevice

Self Verifying Mock Objects

Flash_Program(offset, data)

IOWrite(CommandRegister, 0x40)

IOWrite(offset, data)

IORead(StatusRegister) b7 == 0 IORead(StatusRegister) b7 == 1, other bits == 0 IORead(offset) FlashSuccess data

Repeats while b7 == 0

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Presented at Agile China October 14, 2010 Test Driven Development

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Flash Program Flow Chart How Many Tests are Needed?

Start b3 == 0 Program Command Write 0x40 to 0x0

Mock Object
Problem - Complex collaborator interactions cannot be captured with a simple spy. Solution - Mock Object
A Mock Object is a Test Double that verifies that the code being tested interacts with its collaborator properly. The test tells the mock
The expected calls In the expected order What to return.

NO

Vpp Error

YES
Write data to address

b4 == 0

NO

Program Error

How do you test these errors in the target?

YES
Read status register Protected Block Error

b1 == 0

NO

NO YES
b7 == 1 Start/Stop Clear status Write 0xFF to 0x0

YES
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Flash Driver Test

TEST(Flash, ProgramSucceedsReadyImmediately1) { int result = 0; MockIO_Expect_IOWrite(0, 0x40); MockIO_Expect_IOWrite(0x1000, 0xBEEF); MockIO_Expect_IORead(0, 1<<7); MockIO_Expect_IORead(0x1000, 0xBEEF); result = Flash_Program(0x1000, 0xBEEF); LONGS_EQUAL(0, result); MockIO_Assert_AllExpectationsMet(); }
void void void void void

Mock Flash Read/Write

//MockIO.h #include "IOReadWrite.h" MockIO_Create(int maxExpectations); MockIO_Destroy(); MockIO_Expect_IOWrite(ioAddress_t offset, uint16_t data); MockIO_Expect_IORead(ioAddress_t offset, uint16_t data); MockIO_Assert_AllExpectationsMet();

//IOReadWrite.h #include <stdint.h> typedef uint32_t ioAddress_t; typedef uint16_t ioData_t; ioData_t IORead(ioAddress_t offset ); void IOWrite(ioAddress_t offset, ioData_t data);

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Presented at Agile China October 14, 2010 Test Driven Development

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Mock Flash Read/Write

//MockIO.c typedef struct Expectation { int kind; ioAddress_t addr; ioData_t value; } Expectation; static static static static static Expectation* expectations = 0; int setExpectationCount; int getExpectationCount; int maxExpectationCount; int failureAlreadyReported = 0;

Capturing Flash Read/Write Expectations

void MockIO_Expect_IOWrite(ioAddress_t addr, ioAddress_t value) { failWhenNoMoreRoomForExpectations(report_too_many_write_expectations); recordExpectation(FLASH_WRITE, addr, value); } void MockIO_Expect_IORead(ioAddress_t addr, ioAddress_t value) { failWhenNoMoreRoomForExpectations(report_too_many_read_expectations); recordExpectation(FLASH_READ, addr, value); }

//Snip void MockIO_Create(int maxExpectations) { expectations = malloc(sizeof(Expectation)*maxExpectations); memset(expectations, 0, sizeof(expectations)); setExpectationCount = 0; getExpectationCount = 0; maxExpectationCount = maxExpectations; failureAlreadyReported = 0; }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Monday, October 18, 2010

Mock Flash Read

ioData_t IORead(ioAddress_t addr) { setExpectedAndActual(addr, -1); failWhenNotInitialized(); failWhenNoUnusedExpectations(report_read_but_out_of_expectations); failWhen(expectationIsNot(FLASH_READ), report_expect_write_was_read); failWhen(expectedAddressIsNot(addr), report_read_wrong_address); return expectations[getExpectationCount++].value; }

Mock Flash Write

void IOWrite(ioAddress_t addr, ioData_t value) { setExpectedAndActual(addr, value); failWhenNotInitialized(); failWhenNoUnusedExpectations(report_write_but_out_of_expectations); failWhen(expectationIsNot(FLASH_WRITE), report_expect_read_was_write); failWhen(expectedAddressIsNot(addr), report_write_does_not_match); failWhen(expectedDataIsNot(value), report_write_does_not_match); getExpectationCount++; }

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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Presented at Agile China October 14, 2010 Test Driven Development

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All Expectations Must Be Met

void MockIO_Assert_AllExpectationsMet() { if (failureAlreadyReported) return; failWhenNotAllExpectationsUsed(); }

Minimize DOH!

Debug On Hardware
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On-line
Test harnesses
[CPPTEST] www.sourceforge.org, project CppUTest [FITNESSE] www.fitnesse.org

The End

Groups
http://groups.yahoo.com/group/testdrivendevelopment http://groups.yahoo.com/group/AgileEmbedded

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Presented at Agile China October 14, 2010 Test Driven Development

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See Embedded TDD and Related Blogs and Papers

http://www.renaissanceSoftware.net http://www.renaissancesoftware.net/blog/
Embedded TDD Zune Bug: Test Driven Bug Fix Learning Tests are Free! TDD as a Design Rot Prevention System Crashing Your Way to Great Legacy C Tests TDD and the Big Framework Part Bug Fixes and TDD Physics of Test Driven Development Tests vs. Short Term Cache Between Your Ears Embedded Systems Conference FAQ I miss constructors Who says you cant test drive a device driver? Why are You Still Using C? Planing Poker Agile Embedded Software Development (ESC) Launching Extreme Programming at a Process Intensive Company (IEEE) Test Driven Development for Embedded Software Progress Before Hardware Agile Times - Containing Progress Before Hardware Test-Driven Development for Embedded C++ Programmers

References and Sources

[RCM] Robert C. Martin, Clean Code, 2008 [SLAD] Craig Larman and Bas Voode, Scaling Lean & Agile Development [WELC] Michael Feathers, Working Effectively with Legacy Code [REF] Martin Fowler, Refactoring [TDD] Kent Beck, Test-Driven Development, 2003 [xUNIT] Gerard Meszaros - xUnit Testing Patterns, 2008 [MOCK] Tim Mackinnon and Steve Freeman and Philip Craig, EndoTesting: Unit Testing with Mock Objects, 2001 [TD] Lasse Koskela, Test Driven, 2007 [LESSONS] Bret Pettichord Cem Kaner, James Bach. Lessons Learned in Software Testing: A Context-Driven Approach. John Wiley & Sons, New York, NY, 2002.
Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

www.renaissancesoftware.net james@renaissancesoftware.net

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Monday, October 18, 2010

Available now in Beta

http://pragprog.com/titles/jgade/

In print early 2011

Copyright 2008-2010 James W. Grenning All Rights Reserved. For use by training attendees.

Presented at Agile China October 14, 2010 Test Driven Development

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