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I want to do some tests on our tcl tk application regarding the user interaction. As the application has parts similar to a CAD for which every mouse movement is relevant, I would like to do something like record all events of some user interactions. My goal would be to playback these events laterwards and on every program change to discover potential changes. Or even better to assure the GUI behaves always the same and produces always the same data.
I know, that I can generate some enter motion and button events, but this would not be the same like the thousands of events generated by a real user interaction. But it is very important for me to have exactly these thousands of events.
Is there any possibility to achieve this?
It's relatively easy to record events of particular types with bind — you'll find that <ButtonPress>, <ButtonRelease>, <Enter>, <Leave>, <FocusIn>, <FocusOut>, <KeyPress> and <KeyRelease> cover pretty much everything that you are interested in — and then play them back with event generate. (You need to record quite a bit of information about each event in order to regenerate it correctly, but the underlying model is that of X events with similar names.) Assuming you're not wanting to support inter-application cut-and-paste or drag-and-drop for the purposes of recording; those complicate things a lot. You'll likely have a lot of events; recording to an SQLite database might make a lot of sense.
However, you should think carefully about which parts of the application you want to record. Does it matter if the order of two buttons in the outer shell of the application outside the CAD-like area get swapped in order? For most users, provided you're clear about what the buttons do (through clear labels and icons) it isn't very important, but for replaying recorded events it can matter hugely. Instead, for the parts of the application that are simple buttons and edit fields, I'd not record the details of them but would instead just record when the buttons are clicked and the changes to the text content of entries and so on. In effect, it's capturing higher-level events, and that's much easier to replay correctly. It's only when the user is in that main CAD area that you need the full detail.
Also, beware of changes to font sizes and screen sizes/scaling. They can change how things are laid out and may happen because of system-level alterations outside the scope of your application.
We started out the way you describe: record all those thousands of motion events, etc. Including exact timings which are extremely important for a GUI application as well.
It quickly became appearent that those recordings became too hard to maintain. They are also overly brittle in light of UI changes. Another problem where the hardcoded time values. A switch to a more powerful machine (or a cpu under load) would break the execution.
The two biggest improvements we introduced
Event compression: recognize the high-level action the user wanted to perform (like selecting a menu item). The recorded activateItem command would then perform the necessary work (event emulation) on replay.
Synchronization functions: instead of relying on a particular timing commands like waitForObject wait for an object to come into existance and become ready for interaction.
It took several years for this to work fluently, however. Including a central Object Map repository, property and screenshot verifications, high-level test descriptions in BDD and others. Feel free to take a look a the Squish for Tk product that came out of this work.
I have an HID device that is somewhat unfortunately designed (the Griffin Powermate) in that as you turn it, the input value for the "Rotation Axis" HID element doesn't change unless the speed of rotation dramatically changes or unless the direction changes. It sends many HID reports (angular resolution appears to be about 4deg, in that I get ~90 reports per revolution - not great, but whatever...), but they all report the same value (generally -1 or 1 for CCW and CW respectively -- if you turn faster, it will report -2 & 2, and so on, but you have to turn much faster. As a result of this unfortunate behavior, I'm finding this thing largely useless.
It occurred to me that I might be able to write a background userspace app that seized the physical device and presented another, virtual device with some minor additions so as to cause an input value change for every report (like a wrap-around accumulator, which the HID spec has support for -- God only knows why Griffin didn't do this themselves.)
But I'm not seeing how one would go about creating the kernel side object for the virtual device from userspace, and I'm starting to think it might not be possible. I saw this question, and its indications are not good, but it's low on details.
Alternately, if there's a way for me to spoof reports on the existing device, I suppose that would do it as well, since I could set it back to zero immediately after it reports -1 or 1.
Any ideas?
First of all, you can simulate input events via Quartz Event Services but this might not suffice for your purposes, as that's mainly designed for simulating keyboard and mouse events.
Second, the HID driver family of the IOKit framework contains a user client on the (global) IOHIDResource service, called IOHIDResourceDeviceUserClient. It appears that this can spawn IOHIDUserDevice instances on command from user space. In particular, the userspace IOKitLib contains a IOHIDUserDeviceCreate function which seems to be supposed to be able to do this. The HID family source code even comes with a little demo of this which creates a virtual keyboard of sorts. Unfortunately, although I can get this to build, it fails on the IOHIDUserDeviceCreate call. (I can see in IORegistryExplorer that the IOHIDResourceDeviceUserClient instance is never created.) I've not investigated this further due to lack of time, but it seems worth pursuing if you need its functionality.
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Interview question-
Often its pretty easier to debug a program once you have trouble with your code.You can put watches,breakpoints and etc.Life is much easier because of debugger.
But how to debug a program without a debugger?
One possible approach which I know is simply putting print statements in your code wherever you want to check for the problems.
Are there any other approaches other than this?
As its a general question, its not restricted to any specific language.So please share your thoughts on how you would have done it?
EDIT- While submitting your answer, please mention a useful resource (if you have any) about any concept. e.g. Logging
This will be lot helpful for those who don't know about it at all.(This includes me, in some cases :)
UPDATE: Michal Sznajderhas put a real "best" answer and also made it a community wiki.Really deserves lots of up votes.
Actually you have quite a lot of possibilities. Either with recompilation of source code or without.
With recompilation.
Additional logging. Either into program's logs or using system logging (eg. OutputDebugString or Events Log on Windows). Also use following steps:
Always include timestamp at least up to seconds resolution.
Consider adding thread-id in case of multithreaded apps.
Add some nice output of your structures
Do not print out enums with just %d. Use some ToString() or create some EnumToString() function (whatever suits your language)
... and beware: logging changes timings so in case of heavily multithreading you problems might disappear.
More details on this here.
Introduce more asserts
Unit tests
"Audio-visual" monitoring: if something happens do one of
use buzzer
play system sound
flash some LED by enabling hardware GPIO line (only in embedded scenarios)
Without recompilation
If your application uses network of any kind: Packet Sniffer or I will just choose for you: Wireshark
If you use database: monitor queries send to database and database itself.
Use virtual machines to test exactly the same OS/hardware setup as your system is running on.
Use some kind of system calls monitor. This includes
On Unix box strace or dtrace
On Windows tools from former Sysinternals tools like http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx, ProcessExplorer and alike
In case of Windows GUI stuff: check out Spy++ or for WPF Snoop (although second I didn't use)
Consider using some profiling tools for your platform. It will give you overview on thing happening in your app.
[Real hardcore] Hardware monitoring: use oscilloscope (aka O-Scope) to monitor signals on hardware lines
Source code debugging: you sit down with your source code and just pretend with piece of paper and pencil that you are computer. Its so called code analysis or "on-my-eyes" debugging
Source control debugging. Compare diffs of your code from time when "it" works and now. Bug might be somewhere there.
And some general tips in the end:
Do not forget about Text to Columns and Pivot Table in Excel. Together with some text tools (awk, grep or perl) give you incredible analysis pack. If you have more than 32K records consider using Access as data source.
Basics of Data Warehousing might help. With simple cube you may analyse tons of temporal data in just few minutes.
Dumping your application is worth mentioning. Either as a result of crash or just on regular basis
Always generate you debug symbols (even for release builds).
Almost last but not least: most mayor platforms has some sort of command line debugger always built in (even Windows!). With some tricks like conditional debugging and break-print-continue you can get pretty good result with obscure bugs
And really last but not least: use your brain and question everything.
In general debugging is like science: you do not create it you discover it. Quite often its like looking for a murderer in a criminal case. So buy yourself a hat and never give up.
First of all, what does debugging actually do? Advanced debuggers give you machine hooks to suspend execution, examine variables and potentially modify state of a running program. Most programs don't need all that to debug them. There are many approaches:
Tracing: implement some kind of logging mechanism, or use an existing one such as dtrace(). It usually worth it to implement some kind of printf-like function that can output generally formatted output into a system log. Then just throw state from key points in your program to this log. Believe it or not, in complex programs, this can be more useful than raw debugging with a real debugger. Logs help you know how you got into trouble, while a debugger that traps on a crash assumes you can reverse engineer how you got there from whatever state you are already in. For applications that you use other complex libraries that you don't own that crash in the middle of them, logs are often far more useful. But it requires a certain amount of discipline in writing your log messages.
Program/Library self-awareness: To solve very specific crash events, I often have implemented wrappers on system libraries such as malloc/free/realloc which extensions that can do things like walk memory, detect double frees, attempts to free non-allocated pointers, check for obvious buffer over-runs etc. Often you can do this sort of thing for your important internal data types as well -- typically you can make self-integrity checks for things like linked lists (they can't loop, and they can't point into la-la land.) Even for things like OS synchronization objects, often you only need to know which thread, or what file and line number (capturable by __FILE__, __LINE__) the last user of the synch object was to help you work out a race condition.
If you are insane like me, you could, in fact, implement your own mini-debugger inside of your own program. This is really only an option in a self-reflective programming language, or in languages like C with certain OS-hooks. When compiling C/C++ in Windows/DOS you can implement a "crash-hook" callback which is executed when any program fault is triggered. When you compile your program you can build a .map file to figure out what the relative addresses of all your public functions (so you can work out the loader initial offset by subtracting the address of main() from the address given in your .map file). So when a crash happens (even pressing ^C during a run, for example, so you can find your infinite loops) you can take the stack pointer and scan it for offsets within return addresses. You can usually look at your registers, and implement a simple console to let you examine all this. And voila, you have half of a real debugger implemented. Keep this going and you can reproduce the VxWorks' console debugging mechanism.
Another approach, is logical deduction. This is related to #1. Basically any crash or anomalous behavior in a program occurs when it stops behaving as expected. You need to have some feed back method of knowing when the program is behaving normally then abnormally. Your goal then is to find the exact conditions upon which your program goes from behaving correctly to incorrectly. With printf()/logs, or other feedback (such as enabling a device in an embedded system -- the PC has a speaker, but some motherboards also have a digital display for BIOS stage reporting; embedded systems will often have a COM port that you can use) you can deduce at least binary states of good and bad behavior with respect to the run state of your program through the instrumentation of your program.
A related method is logical deduction with respect to code versions. Often a program was working perfectly at one state, but some later version is not longer working. If you use good source control, and you enforce a "top of tree must always be working" philosophy amongst your programming team, then you can use a binary search to find the exact version of the code at which the failure occurs. You can use diffs then to deduce what code change exposes the error. If the diff is too large, then you have the task of trying to redo that code change in smaller steps where you can apply binary searching more effectively.
Just a couple suggestions:
1) Asserts. This should help you work out general expectations at different states of the program. As well familiarize yourself with the code
2) Unit tests. I have used these at times to dig into new code and test out APIs
One word: Logging.
Your program should write descriptive debug lines which include a timestamp to a log file based on a configurable debug level. Reading the resultant log files gives you information on what happened during the execution of the program. There are logging packages in every common programming language that make this a snap:
Java: log4j
.Net: NLog or log4net
Python: Python Logging
PHP: Pear Logging Framework
Ruby: Ruby Logger
C: log4c
I guess you just have to write fine-grain unit tests.
I also like to write a pretty-printer for my data structures.
I think the rest of the interview might go something like this...
Candidate: So you don't buy debuggers for your developers?
Interviewer: No, they have debuggers.
Candidate: So you are looking for programmers who, out of masochism or chest thumping hamartia, make things complicated on themselves even if they would be less productive?
Interviewer: No, I'm just trying to see if you know what you would do in a situation that will never happen.
Candidate: I suppose I'd add logging or print statements. Can I ask you a similar question?
Interviewer: Sure.
Candidate: How would you recruit a team of developers if you didn't have any appreciable interviewing skill to distinguish good prospects based on relevant information?
Peer review. You have been looking at the code for 8 hours and your brain is just showing you what you want to see in the code. A fresh pair of eyes can make all the difference.
Version control. Especially for large teams. If somebody changed something you rely on but did not tell you it is easy to find a specific change set that caused your trouble by rolling the changes back one by one.
On *nix systems, strace and/or dtrace can tell you an awful lot about the execution of your program and the libraries it uses.
Binary search in time is also a method: If you have your source code stored in a version-control repository, and you know that version 100 worked, but version 200 doesn't, try to see if version 150 works. If it does, the error must be between version 150 and 200, so find version 175 and see if it works... etc.
use println/log in code
use DB explorer to look at data in DB/files
write tests and put asserts in suspicious places
More generally, you can monitor side effects and output of the program, and trigger certain events in the program externally.
A Print statement isn't always appropriate. You might use other forms of output such as writing to the Event Log or a log file, writing to a TCP socket (I have a nice utility that can listen for that type of trace from my program), etc.
For programs that don't have a UI, you can trigger behavior you want to debug by using an external flag such as the existence of a file. You might have the program wait for the file to be created, then run through a behavior you're interested in while logging relevant events.
Another file's existence might trigger the program's internal state to be written to your logging mechanism.
like everyone else said:
Logging
Asserts
Extra Output
&
your favorite task manager or process
explorer
links here and here
Another thing I have not seen mentioned here that I have had to use quite a bit on embedded systems is serial terminals.
You can cannot a serial terminal to just about any type of device on the planet (I have even done it to embedded CPUs for hydraulics, generators, etc). Then you can write out to the serial port and see everything on the terminal.
You can get real fancy and even setup a thread that listens to the serial terminal and responds to commands. I have done this as well and implemented simple commands to dump a list, see internal variables, etc all from a simple 9600 baud RS-232 serial port!
Spy++ (and more recently Snoop for WPF) are tremendous for getting an insight into Windows UI bugs.
A nice read would be Delta Debugging from Andreas Zeller. It's like binary search for debugging
I've been reading about TDD, and would like to use it for my next project, but I'm not sure how to structure my classes with this new paradigm. The language I'd like to use is Java, although the problem is not really language-specific.
The Project
I have a few pieces of hardware that come with a ASCII-over-RS232 interface. I can issue simple commands, and get simple responses, and control them as if from their front panels. Each one has a slightly different syntax and very different sets of commands. My goal is to create an abstraction/interface so I can control them all through a GUI and/or remote procedure calls.
The Problem
I believe the first step is to create an abstract class (I'm bad at names, how about 'Communicator'?) to implement all the stuff like Serial I/O, and then create a subclass for each device. I'm sure it will be a little more complicated than that, but that's the core of the application in my mind.
Now, for unit tests, I don't think I really need the actual hardware or a serial connection. What I'd like to do is hand my Communicators an InputStream and OutputStream (or Reader and Writer) that could be from a serial port, file, stdin/stdout, piped from a test function, whatever. So, would I just have the Communicator constructor take those as inputs? If so, it would be easy to put the responsibility of setting it all up on the testing framework, but for the real thing, who makes the actual connection? A separate constructor? The function calling the constructor again? A separate class who's job it is to 'connect' the Communicator to the correct I/O streams?
Edit
I was about to rewrite the problem section in order to get answers to the question I thought I was asking, but I think I figured it out. I had (correctly?) identified two different functional areas.
1) Dealing with the serial port
2) Communicating with the device (understanding its output & generating commands)
A few months ago, I would have combined it all into one class. My first idea towards breaking away from this was to pass just the IO streams to the class that understands the device, and I couldn't figure out who would then be responsible for creating the streams.
Having done more research on inversion of control, I think I have an answer. Have a separate interface and class that solve problem #1 and pass it to the constructor of the class(es?) that solve problem #2. That way, it's easy to test both separately. #1 by connecting to the actual hardware and allowing the test framework to do different things. #2 can be tested by being given a mock of #1.
Does this sound reasonable? Do I need to share more information?
With TDD, you should let your design emerge, start small, with baby steps and grow your classes test by test, little by little.
CLARIFIED: Start with a concrete class, to send one command, unit test it with a mock or a stub. When it will work enough (perhaps not with all options), test it against your real device, once, to validate your mock/stub/simulator.
Once the class for the first command is operational, start implementing a second command, the same way: first again your mock/stub, then once against the device for validation. Now if you're seeing similarities between your two classes, you can refactor to your abstract class based design - or to something different.
Sorry for being a little Linux centric ..
My favorite way of simulating gadgets is to write character device drivers that simulate their behavior. This also gives you fun abilities, like providing an ioctl() interface that makes the simulated device behave abnormally.
At that point .. from testing to real world, it only matters which device(s) you actually open, read and write.
It should not be too hard to mimic the behavior of your gadgets .. it sounds like they take very basic instructions and return very basic responses. Again, a simple ioctl() could tell the simulated device that its time to misbehave, so you can ensure that your code is handling such events adequately. For instance, fail intentionally on every n'th instruction, where n is randomly selected upon the call to ioctl().
After seeing your edits I think you are heading in exactly the right direction. TDD tends to drive you towards a design composed of small classes with a well-defined responsibility. I would also echo tinkertim's advice - a device simulator which you can control and "provoke" into behaving in different ways is invaluable for testing.
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What is your best practical user-friendly user-interface design or principle?
Please submit those practices that you find actually makes things really useful - no matter what - if it works for your users, share it!
Summary/Collation
Principles
KISS.
Be clear and specific in what an option will achieve: for example, use verbs that indicate the action that will follow on a choice (see: Impl. 1).
Use obvious default actions appropriate to what the user needs/wants to achieve.
Fit the appearance and behavior of the UI to the environment/process/audience: stand-alone application, web-page, portable, scientific analysis, flash-game, professionals/children, ...
Reduce the learning curve of a new user.
Rather than disabling or hiding options, consider giving a helpful message where the user can have alternatives, but only where those alternatives exist. If no alternatives are available, its better to disable the option - which visually then states that the option is not available - do not hide the unavailable options, rather explain in a mouse-over popup why it is disabled.
Stay consistent and conform to practices, and placement of controls, as is implemented in widely-used successful applications.
Lead the expectations of the user and let your program behave according to those expectations.
Stick to the vocabulary and knowledge of the user and do not use programmer/implementation terminology.
Follow basic design principles: contrast (obviousness), repetition (consistency), alignment (appearance), and proximity (grouping).
Implementation
(See answer by paiNie) "Try to use verbs in your dialog boxes."
Allow/implement undo and redo.
References
Windows Vista User Experience Guidelines [http://msdn.microsoft.com/en-us/library/aa511258.aspx]
Dutch websites - "Drempelvrij" guidelines [http://www.drempelvrij.nl/richtlijnen]
Web Content Accessibility Guidelines (WCAG 1.0) [http://www.w3.org/TR/WCAG10/]
Consistence [http://www.amazon.com/Design-Everyday-Things-Donald-Norman/dp/0385267746]
Don't make me Think [http://www.amazon.com/Dont-Make-Me-Think-Usability/dp/0321344758/ref=pdbbssr_1?ie=UTF8&s=books&qid=1221726383&sr=8-1]
Be powerful and simple [http://msdn.microsoft.com/en-us/library/aa511332.aspx]
Gestalt design laws [http://www.squidoo.com/gestaltlaws]
I test my GUI against my grandma.
Try to use verbs in your dialog boxes.
It means use
instead of
Follow basic design principles
Contrast - Make things that are different look different
Repetition - Repeat the same style in a screen and for other screens
Alignment - Line screen elements up! Yes, that includes text, images, controls and labels.
Proximity - Group related elements together. A set of input fields to enter an address should be grouped together and be distinct from the group of input fields to enter credit card info. This is basic Gestalt Design Laws.
Never ask "Are you sure?". Just allow unlimited, reliable undo/redo.
Try to think about what your user wants to achieve instead of what the requirements are.
The user will enter your system and use it to achieve a goal. When you open up calc you need to make a simple fast calculation 90% of the time so that's why by default it is set to simple mode.
So don't think about what the application must do but think about the user which will be doing it, probably bored, and try to design based on what his intentions are, try to make his life easier.
If you're doing anything for the web, or any front-facing software application for that matter, you really owe it to yourself to read...
Don't make me think - Steve Krug
Breadcrumbs in webapps:
Tell -> The -> User -> Where -> She -> Is in the system
This is pretty hard to do in "dynamic" systems with multiple paths to the same data, but it often helps navigate the system.
I try to adapt to the environment.
When developing for an Windows application, I use the Windows Vista User Experience Guidelines but when I'm developing an web application I use the appropriate guidelines, because I develop Dutch websites I use the "Drempelvrij" guidelines which are based on the Web Content Accessibility Guidelines (WCAG 1.0) by the World Wide Web Consortium (W3C).
The reason I do this is to reduce the learning curve of a new user.
I would recommend to get a good solid understanding of GUI design by reading the book The Design of Everyday Things. Although the main printable is a comment from Joel Spolsky: When the behavior of the application differs to what the user expects to happen then you have a problem with your graphical user interface.
The best example is, when somebody swaps around the OK and Cancel button on some web sites. The user expects the OK button to be on the left, and the Cancel button to be on the right. So in short, when the application behavior differs to what the user expects what to happen then you have a user interface design problem.
Although, the best advice, in no matter what design or design pattern you follow, is to keep the design and conventions consistent throughout the application.
Avoid asking the user to make choices whenever you can (i.e. don't create a fork with a configuration dialog!)
For every option and every message box, ask yourself: can I instead come up with some reasonable default behavior that
makes sense?
does not get in the user's way?
is easy enough to learn that it costs little to the user that I impose this on him?
I can use my Palm handheld as an example: the settings are really minimalistic, and I'm quite happy with that. The basic applications are well designed enough that I can simply use them without feeling the need for tweaking. Ok, there are some things I can't do, and in fact I sort of had to adapt myself to the tool (instead of the opposite), but in the end this really makes my life easier.
This website is another example: you can't configure anything, and yet I find it really nice to use.
Reasonable defaults can be hard to figure out, and simple usability tests can provide a lot of clues to help you with that.
Show the interface to a sample of users. Ask them to perform a typical task. Watch for their mistakes. Listen to their comments. Make changes and repeat.
The Design of Everyday Things - Donald Norman
A canon of design lore and the basis of many HCI courses at universities around the world. You won't design a great GUI in five minutes with a few comments from a web forum, but some principles will get your thinking pointed the right way.
--
MC
When constructing error messages make the error message be
the answers to these 3 questions (in that order):
What happened?
Why did it happen?
What can be done about it?
This is from "Human Interface Guidelines: The Apple Desktop
Interface" (1987, ISBN 0-201-17753-6), but it can be used
for any error message anywhere.
There is an updated version for Mac OS X.
The Microsoft page
User Interface Messages
says the same thing: "... in the case of an error message,
you should include the issue, the cause, and the user action
to correct the problem."
Also include any information that is known by the program,
not just some fixed string. E.g. for the "Why did it happen" part of the error message use "Raw spectrum file
L:\refDataForMascotParser\TripleEncoding\Q1LCMS190203_01Doub
leArg.wiff does not exist" instead of just "File does
not exist".
Contrast this with the infamous error message: "An error
happend.".
(Stolen from Joel :o) )
Don't disable/remove options - rather give a helpful message when the user click/select it.
As my data structure professor pointed today: Give instructions on how your program works to the average user. We programmers often think we're pretty logical with our programs, but the average user probably won't know what to do.
Use discreet/simple animated features to create seamless transitions from one section the the other. This helps the user to create a mental map of navigation/structure.
Use short (one word if possible) titles on the buttons that describe clearly the essence of the action.
Use semantic zooming where possible (a good example is how zooming works on Google/Bing maps, where more information is visible when you focus on an area).
Create at least two ways to navigate: Vertical and horizontal. Vertical when you navigate between different sections and horizontal when you navigate within the contents of the section or subsection.
Always keep the main options nodes of your structure visible (where the size of the screen and the type of device allows it).
When you go deep into the structure always keep a visible hint (i.e. such as in the form of a path) indicating where you are.
Hide elements when you want the user to focus on data (such as reading an article or viewing a project). - however beware of point #5 and #4.
Be Powerful and Simple
Oh, and hire a designer / learn design skills. :)
With GUIs, standards are kind of platform specific. E.g. While developing GUI in Eclipse this link provides decent guideline.
I've read most of the above and one thing that I'm not seeing mentioned:
If users are meant to use the interface ONCE, showing only what they need to use if possible is great.
If the user interface is going to be used repeatedly by the same user, but maybe not very often, disabling controls is better than hiding them: the user interface changing and hidden features not being obvious (or remembered) by an occasional user is frustrating to the user.
If the user interface is going to be used VERY REGULARLY by the same user (and there is not a lot of turnover in the job i.e. not a lot of new users coming online all the time) disabling controls is absolutely helpful and the user will become accustomed to the reasons why things happen but preventing them from using controls accidentally in improper contexts appreciated and prevents errors.
Just my opinion, but it all goes back to understanding your user profile, not just what a single user session might entail.