A small tutorial about systematic development and testing of embedded software using state machines

1. Introduction to State
Machines

2. About Swift Act LLC
Introduction to State Machine @ Swift Act LLC
❑ Established @ end of 2017
❑ Legal representation in Egypt and Germany
❑ Experience in Automotive, Industrial Automation, IoT, consumer electronics …
❑ Safety critical experience: IEC 61508, ISO 26262 ...
❑ Process compliance: A-SPICE and CMMI
❑ Mission: Long-term partnership with stakeholders
❑ Vision: Maximizing value for stakeholders
❑ Values: Ethics, Empowerment, Professionalism, Team Work and Trust
❑ www.swift-act.com

3. What is a State Machine?
Introduction to State Machine @ Swift Act LLC

4. Why a State Machine?
Introduction to State Machine @ Swift Act LLC

5. State Machines are Hierarchical
Introduction to State Machine @ Swift Act LLC

6. State Machines are Concurrent
Introduction to State Machine @ Swift Act LLC

7. State Machine Elements
Introduction to State Machine @ Swift Act LLC
S/M
Elements
States
Transitions
Events
Actions

8. States are ...
Introduction to State Machine @ Swift Act LLC
States
Finite
Distinct
1 or more
initial states
0 or more
end states
0 or more
intermediate
states

9. State Machine Graphical Representation
Introduction to State Machine @ Swift Act LLC
Stopped Playing
Paused
Play/Song is Playing from beginning
Stop or Song Finished/Song
is Stopped
Pause/Song is Paused
Play/Song is Resumed
Stop/Song is Stopped

10. State Machine Tabular Representation
Introduction to State Machine @ Swift Act LLC
Current State Event Action Next State
Stopped Play
Play song from
beginning
Playing
Stopped Pause Stopped
Stopped Stop Stopped
Stopped Song finished Stopped
Playing Play Playing
Playing Pause Song is paused Paused
Playing Stop Song is stopped Stopped
Playing Song finished Song is stopped Stopped
Paused Play Song is resumed Playing
Paused Pause Paused
Paused Stop Song is stopped Stopped
Paused Song finished Paused

11. State Machine Textual Representation
Introduction to State Machine @ Swift Act LLC

12. State Machine from Design PoV
Introduction to State Machine @ Swift Act LLC
Events Timing events only?
Input events only?
Timing and input events

13. State Machine from Coding PoV
Introduction to State Machine @ Swift Act LLC
Function
for
every
state?
Similar? 1 function + Data
Different? State type + State
variable + function
(switch-case) +
function for every
state (optional)

14. Data-Indexed State Machine Example
Introduction to State Machine @ Swift Act LLC

15. Data-Indexed State Machine Example cont’d
Introduction to State Machine @ Swift Act LLC

16. Execution-Indexed State Machine Example
Introduction to State Machine @ Swift Act LLC

17. Execution-Indexed State Machine Example cont’d
Introduction to State Machine @ Swift Act LLC

18. Remember: State Machines are Hierarchical
Introduction to State Machine @ Swift Act LLC

19. Testing State Machine – Coverage Methods
Introduction to State Machine @ Swift Act LLC
• States
• Events
• Actions
• Paths

20. Testing State Machine – Coverage Methods cont’d
Introduction to State Machine @ Swift Act LLC
• States
• Events
• Actions
• Paths

21. Testing State Machine – Coverage Methods cont’d
Introduction to State Machine @ Swift Act LLC
• States
• Events
• Actions
• Paths

22. Testing State Machine – Coverage Methods cont’d
Introduction to State Machine @ Swift Act LLC
• States
• Events
• Actions
• Paths

23. Transition Coverage: n-switch (+ve Testing)
Introduction to State Machine @ Swift Act LLC
A
B
C
D
F
E
1
2
9
8
10
3
14
11
4
13
5
12
7
6

24. Transition Coverage: 0-switch vs. 1-switch
Introduction to State Machine @ Swift Act LLC
0-switch 1-switch
A1 A2 A9 A1A1 A1A2 A1A9 A9B10 A9B8 A9B3
B10 B8 B3 B10C14 B10C11 B10C4 B8A1 B8A2 B8A9
C14 C11 C4 C14C14 C14C11 C14C4 C11D13 C11D12 C11D5
D13 D12 D5 D13D13 D13D12 D13D5 D12F6 D12F7
F6 F7 F7A1 F7A2 F7A9

25. 0-switch: Systematic Way
Introduction to State Machine @ Swift Act LLC
1
3
2
4
1
3 4
1212
13
13
12

26. n-switch: Systematic Way
Introduction to State Machine @ Swift Act LLC
(N-1)-
switch
Extra
level in
the tree
N-
switch

27. -ve Testing
Introduction to State Machine @ Swift Act LLC
-ve Testing
Testing
Invalid
Transitions

28. Case Study: Digital Clock
Introduction to State Machine @ Swift Act LLC
Digital ClockSet Button
+ Button
- Button
Hours Units SSD
Minutes Tens SSD
Hours Tens SSD
Minutes Units SSD

29. Case Study: Block Diagram
Introduction to State Machine @ Swift Act LLC
Digital Clock
SW
Time
SSD
Display

30. Case Study: SW
Introduction to State Machine @ Swift Act LLC

31. Case Study: SSD
Introduction to State Machine @ Swift Act LLC

32. Case Study: Time
Introduction to State Machine @ Swift Act LLC
Set Hours
Set
Minutes
Normal
Set is pressed
Set is pressed
Set is pressed

33. Case Study: Display
Introduction to State Machine @ Swift Act LLC
Blink
Hours
Blink
Minutes
Blink
Seconds
Time mode = Set Hours
Time mode = Set Minutes
Time mode = Normal

34. Introduction to State Machine @ Swift Act LLC