Categories
Blog posts in English

Death by Virtual Memory

Every pc user knows that pc’s become slower and slower over time until the point where they are almost unusable. This is where upgrading RAM will usually help – until eventually you have to buy a new pc. Apparantly that’s just the way pc’s wear out.
Actually, pc’s don’t wear out – readers of my blog probably know that, but users (knowingly and unknowingly) add software which consumes resources of which memory is the most important one.
RAM used to be very expensive and therefore a scarce resource. Programmers used to do all sorts of tricks to fit their increasingly complex programs in memory. To help them focus on the programming task and not worry too much about resource scarcity, operating system designers invented something called virtual memory or swap memory.
Swap memory allowed the operating system to remove running processes from the (expensive and therefor scarce) RAM and store the state of the process on disk (‘swap’ it out – hence the name), from where it could later be restored into RAM and start running on the cpu. The technique is still employed by all modern operating systems, and while the amount of RAM has grown considerably to a level where lack of it is usually not a problem, virtual memory techniques are still useful with long running processes that only need to run once in a while and where it is not a problem if the initial response time is a second or more – and when they’re not running, the RAM can be used for caching file system data and other important things.
But what happens if load increases, e.g. if the number of users grow or the system becomes otherwise loaded and the processes running on the system start competing for memory? The good news is that functionally nothing changes: Virtual memory is transparant to the process, so the code will execute the same as it did before. But the bad news is that execution time increases rapidly when real memory become exhausted and the OS has to start using VM. If this only happens during nighttime or at other times when users or external systems are’nt depending on the system, all is probably okay, but if not then you can be in real trouble. In fact, the problem can be so bad that the system becomes useless.
In fact, with much more RAM and larger programs in today’s computers, the relative performance penalty is much higher than it used to be. This is because when the OS starts swapping, the amount of data that needs to be transferred in and out of the hard disk(s) is probably a factor of 10 higher than it would have been say 10 years ago. During that time, however, hard disk access speeds has only doubled, so overall, the damage you risk of hitting the virtual memory “wall” is much higher now than it used to be.
An interesting factor which I have found useful to look for is the fact that anti virus systems installed on your servers often make the virutal memory problem worse. They do so because they install hooks into applications running on the system, monitoring all i/o. This monitoring performs well as long as the anti virus system can keep its database and code in memory, but when memory starvation starts occurring, it can turn into a real bad situation. How can we detect that situation (except by performance dropping)?
I’m not aware of any really useful tools that can sit in the background automatically detecting (or better: predicting) memory starvation problems on running servers or test systems. But there are ways to look for it: On Windows, I’ll be looking at the running processes, particularly focusing on the Page Faults Delta column, looking for processes consistently experiencing high numbers here:

This is an important performance testing subject. And one which is too often overlooked.

Categories
Blog posts in English

Importance of simplicity and usability

I came across this on a web site today:

I think among the reasons [insert product name] works so well is that it was developed not by endless betas and adding too many features requested by wankers who do nothing but play on their computers, but instead by people who understand the importance of simplicity and usability.
[Insert product name] has exactly what I need in a simple enough form that I can figure it out.

The product in question is Apple’s Aperture, but that’s not important. But Ken Rockwell (who wrote this) “even dream in Photoshop”. It’s a big statement.
This is about shifting focus to from technology to product value. Looking at myself in the mirror, I hope I won’t see a “wanker” who makes computer systems just for the fun of playing with technology. But I know the feeling. After all, it was the passion for technology that started my computer career almost 30 years ago. In that respect, I hope I’ve grown up a bit! 😉

Categories
Blog posts in English

Teaching Testing to Teenagers

I had the opportunity of being teacher for my son Frederik’s 7th grade class today at Kvikmarken. The school had decided to send the ”real” teachers on a workshop together, so the job of teaching the children was left to volounteering parents. I’m enthusiastic about learning, so felt obliged to volunteer.
I gave them a crash course in software testing.

Software on punched paper tape from the mid 1960's

These boys and girls are really smart. They quickly grasped an understanding of what software testing is about: Exploring and learning. Remember, they are brought up with laptops, mobile phones, and the internet, so they’ve learned to cope with all the shortcomings and bugs that come with today’s technology. I could have expected them to be blind of bugs. But no, they do see them – and they are splendid explorers and learners.
I started my lesson with a flash back 40-50 years ago when computers were as big as a classroom and software was written on note paper and stored on punched tape. I compared this with today’s state of the art commodity computer: An iPad, smaller than a school book – and a lot more powerful than computers then.
Complexity has increased by a factor of at least one million – and it shows! (Though I should add that the evolution of software development tools and methods has also improved a good deal.)
They now know what a bug is, why there are bugs in software, what testing is about and how testing is a learning and discovery process. They also have an idea of why we’re testing – they particularly liked this one: We test because it feels good to break stuff!
Finally, the had a chance to prove their collective exploration abilities in a testing exercise. They did splendidly!
The last slide of my presentation contained a quote from James Bach on Twitter yesterday, words of a true tester on bug hunt using his senses:

Say “it looks bad” and I hear you.
Say “it smells bad” and I taste BLOOD.

I’m happy that Frederik’s classmatetes liked my lesson: ”Great presentation, thanks!”, ”Wow, testing is fun!”, ”You’ve got a really cool job!”
I think there’s good reason to expect software engineering to improve a lot when these boys and girls get to be responsible for software engineering!

Categories
Blog posts in English

Peugeot's Black Swan at Le Mans 2010

This blog post is  about motorsport. What does motorsport have to do with software engineering, you ask? Read on!
I’m a big fan of motorsport and Le Mans 24 hours in particular.  Le Mans is a 24 hours motor race with about 50 race cars of four different classes competing in the same race. Le Mans is also a legend, run first time in the 1920’s. To run a race over 24 hours is very challenging for teams and machinery. An F1 race is only 2 hours and cars are only a bit faster. We’re 240,000 spectators, and about 40,000 danes travel the 1500 km to get there – including me and two of my boys, so it’s also a big, great party.

My son Aksel at Le Mans 2010
My son Aksel (very focused - and a bit tired from a long drive) at Le Mans 2010

 
But to me as an engineer, Le Mans is also intellectually inspiring. Le Mans is a reminder that while we can do a lot with technology, there’s also a lot that we can’t do and that the laws of physics will always set a limit on the track. In order to try to win, race car manufacturers and teams will constantly try to push that limit, but it will always be there.
When cars are withdrawn from an F1 race, its typically because of an accident – drivers making mistakes. While driver mistakes are unavoidable over such a long race, withdrawals are actually more common due to technical reasons: The equipment breaking down, engines blowing up, or just electrical gremlins pulling the plug. The fascinating part is that it has been like this since the very beginning.
So failures are more or less expected. 50 cars at the start line, and usually only some 25 at the finish. But Le Mans 2010 was a little different: It was Peugeots ”Black Swan Year”.
The Peugeot 908’s were again extremely fast, perfectly tuned, and ready to race. Audi had gone through a challenging development process with their new R15, which turned out to not be as fast as they had had hoped it would be in 2009, but was improved in 2010, so we all thought that 2010 was to be a year where Audi would be able to compete with Peugeot on speed. But Peugeot again set impressive lap times never before seen at Le Mans. Couple that with the fact that their team finally seemed to be a well working machine now (proved by the 2009 overall win), so it seemed that Audi could only hope for a podium.
Until a conrod broke on the leadning Peugeot at Tertre Rouge on Sunday morning. I was there with my camera, enjoying the early morning and the race, but I left that area only 10 minutes before so I didn’t have a chance to catch the action (aren’t you always in the wrong place at the right time?).
It came as a shock to everyone. I watched the TV pictures on the big screens around the track showing the team completely in shock about what had happened, and I looked down into the pit area where the Eurosport TV crew was trying to get comments from the team which seemed to be paralyzed. But it seemed to be a coincidence at the time. Until a few hours later when another Peugeot failed in a similar way. We started wondering what was going on? And with only one hour remaining of the race, the customer entered Peugeot 908 failed and the race was lost. Audi won 1-2-3 with their three R15+ cars.
It was devastating. The Peugeot Sport director was seen crying on TV. The french spectators and press went home early from the race. This was a nation loosing a battle with their negihbors.
Of course we didn’t know the technical reason why all Peugeots had failed at the race, but it seemed as if they had been ‘programmed’ to fail. About a month later, Peugeot released a statement that the three cars had suffered from the same failure and that the fourth car (which retired before the others due to a broken suspension) would have suffered the same problem if it had still been running during Sunday. Peugeot said that the breakdown came as a surprise. That they had tested the cars and engines and never expected this. I’m sure it was a surprise. I’m also sure their sports director didn’t expect this embarrasing disaster in front a whole nation of supporters. I’m sure they thought everything was Hunky-dory.
But at the same time, I’m not in doubt that the problem was rooted in history: That an engineer somewhere knew that there was a risk, but for reasons which are probably rooted in group thinking and organisational behaviour, kept the knowledge to himself – or simply chose to ignore it. Conrods have failed in cars since the first reciprocating engine was built, but engineers have learnt to handle this so today we have reliable engines that can easily do more than 300,000 km. When engineering has made something inherently unreliable reliable, people tend to forget about it. Management expect it to be under control.
This is true even for competetion engines, even though they are of course pushed much more and designed to be minimal and as light as possible in order to promote power output: I’m sure Peugeot management thought the conrod supplier had everything under control, which they might have had – but they could have worked to meet the wrong specification. We won’t know the details, and it’s not important either.
To win Le Mans you have to be running at the end. The Peugeots didn’t. They obviously forgot what it takes to make something inherently unreliable reliable: It takes focus on what can possibly go wrong. Software is not different: When software fails, it’s often also because someone forgot to raise and issue or because someone chose to ignore it. Many disasters in systems are rooted in history, which also means that they could have been prevented.
 This is where professional pessimists on a team can help. Where testers’ negative attitude can mean the difference between success and failure.
For me, Peugeot’s black swan event at Le Mans 2010 is a reminder that we all have shared responsibility for seeking out and communicating these details. By testing, careful inspection, talking to developers and users, and by constantly focusing on problems. We’re on a mission to prevent disaster by making the risks known so managers can take informed descisions.
Le Mans 2011 will be interesting in a new way since the cars will be technologically different with hybrid engines. This is new technology, so we should probably expect it to fail more at random or just affect performance during the race: Longer pitstops and the like. But lets see, it’s a big and long race. Anything can happen! I’ve got our tickets booked, so let me know if you’ll be at Le Mans in June – and we can meet up and enjoy the cars. And perhaps discuss engineering and testing?
Leading Peugeot 908 photographed at Tertre Rouge Sunday morning at Le Mans 24h 2010 - just prior to failing
Leading Peugeot 908 caught by me and my Nikon on Sunday morning only about 30 minutes before it failed at the same location

Categories
Blog posts in English

Skype's first Black Swan

Skype went out for about 24 hours just before Christmas. Skype management is embarrassed and promise this will not happen again, which of course is true. The particuar situation is now prevented. However, the question is: Will Skype never be out again?
Skype’s CIO explains what went wrong in this post mortem of what I’d call Skype’s first Black Swan.
To summarise, it was a high load on Skypes infrastructure which triggered a bug in a certain version of the Windows client for Skype which again increased the load on the infrastructure, thereby rapidly taking the entire network down and making it almost impossible to get it up again.
The bug was always there of course, and it was probably already known internally at Skype. It is also possible that the risk of server overloading and service degradation had been identified, but obviously not in the context of making a complete system crash a likely possibility (if so, they would have prevented it). Further, I’m quite certain that the risk of the client bug affecting the server load had not been identified. Humans are positive thinkers, as Taleb documents in his book: The Black Swan: The Impact of the Highly Improbable.
So Skype’s challenge now is to prevent outages in general by identifying and preventing Black Swans in general. This will involve a cross organisational backwards thinking process, which the innovation driven company has probably not been focusing on at all until now. (I may actually be wrong here, Janus Friis, one of the founders of Skype, used to work in a support function of an ISP so he may have been involved in preventing problems, but generally, startups think very positively, and even if Skype has millions of users, it’s still a very young company – a startup.)
One may think that this is going to be extremely expensive for Skype since they will have to predict every possible way their system can go wrong. It does not have to be that expensive, although it will cost money.
When securing a nuclear facility, engineers don’t have to analyze every possible way a disaster can happen, instead they think: How can we prevent failure at every level? This is what I mean with “backwards thinking” – start assuming something is failing, then work backwards identifying ways to prevent it becoming worse.
This is done on multiple levels: On component level, asking what can go wrong here and how can we prevent a bug or incident from affecting the rest of the system? And on system level, assuming that disaster is happning, how can we prevent it from developing.
I assume that’s what Skype is doing now.
Wishing everyone a happy 2011!

Categories
Blog posts in English

Bohr on testing

When Niels Bohr and his team of geniuses at his institute in Copenhagen  developed quantum physics, they fundamentally changed science by proving wrong an assumption dating very far back in science: That everything happens for a reason. In science, building and verifying models to predict events based on knowledge of variables is an important activity, and while this is still meaningful in certain situations, quantum mechanics proved that on the microscopic level of atoms and particles, things don’t happen for a reason. Put in another way: You can have effects without cause. In fact, effects don’t have causes as such at this level.
This means that in particle physics, you cannot predict precisely what’s going to happen, even if you know all variables of a system. Well in fact you can, but only if you’re prepared to give up knowing anything about when and where the effect will happen.
This is counterintuitive to our daily understanding of how the world works. But there’s more: According to quantum physics, it is impossible to seperate knowledge of variables of a system from the system itself. The observation of the system is always part of the system, and thus changes the system in an unpredictable way.
If you find this to be confusing, don’t be embarrassed. Even Einstein never accepted this lack of causality.
Bohr was a great scientist, but he was also a great philosopher. He did a lot of thinking about what this lack of causaility and the inseperability of observation from events would teach us about our understanding of nature. On several occasions he pointed out that even on the macroscopic level, we cannot ignore what is happening on the atomic and particle level. First of all because quantum physics did away with causality as a fundamental principle, but also because quantum effects are in fact visible to us in our daily macroscopic life: He used the example of the eye being able to react on stimuli as small as those of a single photon and argued that it is very likely that the entire organism contains other such amplification systems where microscopic events have macroscopic effects. In some of his philosophical essays he points out how psychology and quantum mechanics follow similar patterns of logic.
So does testing. In software testing we are working to find out how a compuster system is working. Computers are algorithmic machines designed in such a way that randomness is eliminated and data can be measured (read) without affecting the data, but the programs are written by humans and are used by humans, so the system in which the computer program is used is both complex and inherently unpredictable.
We’re also affecting what we’re testing. Not by affecting the computer system itself, but by affecting the development of the software by discovering facts about the system and how it works in relation to other systems and the users.
In some schools of software testing, the activity is reduced to a predictable one: Some advocate having “a single point of truth” about what is going to be developed in an iteration, and that tests should verify that implementation is correct – nothing more. They beleive that it is possible to assemble “all information” about a system before development starts, and that any information not present is not a requirement and as such should not be part of the delivery.
That is an incorrect approach to software engineering and to testing in particular. Testing is much more than verification of implementation, and the results of testing are as unpredictable as the development process itself is. We must also remember that it is fundamentally impossible to collect all requirements about a product: We can increase the probability of getting a well working system by collecting as much information as possible about how the system should work and how it is actually working (by testing), and comparing the two, but the information will always be fundamentally incomplete.
Fortunately we’re not stupid. It is consistent with quantum physics.
Studying the fundamental mechanisms of nature can lead to a better understanding of what we are working with as software engineers and as software testers in particular.

My son Jens at Tisvilde beach, where Niels Bohr spent a lot of time with friends, familiy and physicists

Categories
Blog posts in English

Finding the perfects

Friend and tester colleague Jesper Ottosen participated in what appeared to be a great event and discussion at EuroStar 2010: The rebel alliance night (link to Shmuel Gershon’s blog with video recordings of the talks), where he spoke about whether we as testers can start looking for more than defects. What if we started looking for the perfects?
I like the idea: Is testing really only about finding problems? It can be depressing to be the one always to tell the bad news (especially when there is a lot of bad news or the bad news are not really welcome). Do we testers really have to be worried all the time? If we start communicating perfects too, will our careers not get both better and more successful?
I see a problem, though. Looking for good things will be in conflict with the very mindset of testing. Programming is a creative process where the programmer creates something new and unique. He does it to solve a problem and he does it in the assumption that it will solve the problem. If he starts out assuming that it won’t work, he will be psychologically blocking his creativity and he will probably not perform well.
As a tester, I look at software with the reverse assumtion: I assume that it will not work. This assumption is stimulating my creativity to find the bugs because I will get ideas of where they’re hiding.
With that assumption, I just can’t be successful looking for good things!
That said, however, I do beleive that we sometimes need to be positive, especially to satisfy some managers and programmers. They’re used to hear bad news from us and some people can’t take that. Switching for a moment to looking for “perfects” might actually work very well in this respect. Just don’t forget that we’re doing it for them, not to do our job.
And don’t forget that it can only be for a while: We have to think negatively to be successful. We make a difference when we find the obvious problems with the product: The problems that will cause severe dissatisfaction among users and managers if they slip into product. We’re a great help to our clients because we prevent bugs by finding them before the users!
Here’s Jesper at EuroStar 2010:
[youtube=http://www.youtube.com/watch?v=wB_N-TZPde8&fs=1&hl=da_DK&color1=0x5d1719&color2=0xcd311b]

Categories
Blog posts in English

Based on evidence…

I’m very interested in shool education and I’m chairing the board of the local school. My particular field of interest is education for children with learning disabilities. This is because two of my boys have ADHD with reading disabilities.
We’re looking for new ways to educate children with special needs here in Denmark, and the trend is to include them in the normal educational environment – not put them in special schools. There are two reasons to do so: One is that it’s cheaper, the other that the effect of special education is statistically not very good.
I’m regularly discussing the dilemmas of special education with local politician and social sciences professor Bent Greve, and lately he and I had a short e-mail discussion about whether education should be evidence based. This is also a public debate, similar in nature to the debate taking place in the testing community.
Bent Greve explained me why he, as a politician, requires education to be evidence based: He needs to know that the practices which are being applied actually works. I suppose it is about supporting his descision making, but he pointed out that it is also in the interest of those they’re trying to help. It can be done in health care, so he beleives it can be done in other areas too. However, it should never be an excuse for the individual professionals’ responsibility for what he or she is doing – the evidence should support them in making the right decisions.
This point of view is sympathetic if you’re engaged in politics or managing a company: You want your workers to do work that works. Not work that doesn’t work. Right?
On the other hand is the point of view of the professional, who uses his talent and creativity to research for and find solutions. Teachers generally argue against the focus on evidence and find that it limits their freedom and makes them less good teachers. I also argued with Bent that, sometimes the “right descision” turns out to be the wrong descision. For example: If you base your teaching on evidence of what works in general, we can be certain that there will be between 5 and 20% of the pupils who will not learn anything. So what should we do for them?
Bent Greve responded intelligently: Evaluation and evidence cannot be left alone. Continous experimentation and development is needed, as nothing can be said to be final truths.
I agree.
As a tester craftsman I follow patterns in my work which work for me most of the time, but sometimes I find that they don’t. If I test and don’t find any bugs, I feel dissatisfied and confused. I think I may have used the wrong pattern, but I’m in jeopardy and I don’t know what to do since my pattern failed. Eventually I may have to give up, or I may discover a pattern that works within the time that I have to test.
Managers don’t find bugs, testers do. Politicians don’t educate pupils, teachers do. So who should we trust? I’m not going to answer this question since it’s absurd: There would not have been schools if there hadn’t been politicians and there would not have been any software companies if there were no managers. But I think everyone can agree that by the end of the day, the thing that really matters is that we find as many of those annoying bugs as possible before the product is released, and that the pupils learn the most from attending school. Right?
Correct. But sometimes we find that the patterns we’re following in our worklife (whether that’s teaching or testing) are not working. Then what? We have to stop and think. Something is wrong. How do we progress from here. This is where the most important rule is: Don’t apply the same pattern again – try something different!
PS: I was not at Eurostar 2010 today so did not hear Stuart Reid’s keynote. I did, however follow some of the noise it caused on Twitter!

Copyright (C) Anders Dinsen
6 year old Troels learning by playing

Categories
Blog posts in English

Usability testing is different

Usability testing is done for roughly the same reason as other kinds of testing: To discover new knowledge about the system under test. In this case knowledge about how users work with the system.
But Usability Testing is a very different discipline from ordinary system testing.
In my opinion, the one thing that makes usability testing different from system testing is, that it never discovers absolute facts about the system. 
Instead, a usability test will only say something about how the system works in relation to someone – and this someone is a person – or persons. And as you have probably experienced several times in your life, real persons aren’t absolute, predictable, or static – they’re quite dynamic and you never really know what to expect. Usability testing is a bit like integration testing against a remote system, which keeps changing, even while you test it!
Another aspect is that it’s much more important, yet also more difficult, to describe the context in which the system is to be used and the test is executed in.
I’ll illustrate that with a basic example: Many corporations implement systems for internal use which are not really user friendly, but since the employees get paid for using them, they don’t mind this – and once they’ve used the system for a few weeks, the system may have become an efficient work tool. An opposite example is most computer games, which are deliberately designed to be inefficient, but are usually easy to learn and use. These two systems or applications may be used on the same day by the same person, but in different situations, of course.
Setting the context is not always possible, though. For example is that most people will only respond to things which they understand: Chances are that if you had tested Facebook on users in 1995, they wouldn’t like it at all because they would not understand what it was to be useful for.
Essentially, I feel that the tester must be much more conscious about what he is doing and how it is affeting the test results. I actually believe that the description of the context itself and the way you describe it is as influential on the results you get, as the system and the users themselves.
Yes, testing usability can be very challenging!

Categories
Blog posts in English

Code is Poetry – But What About Testing?

WordPress used to have a tagline saying “code is poetry”, apparantly Microsft has used it too. I don’t know who came up with it first, but I agree. I wrote my first piece of BASIC code almost 30 years ago, my first machine code program more than 25 years ago, and learned C also about 25 years ago. Code can be as meaningful and meaningless as poetry, so the analogy is correct. To me at least.
Now, many years later, I’m a professional tester. I find problems with other peoples business processes, architecture, software designs, and implementations. I don’t write code any more (except when I’m using it to test something).
But where’s the poetry? Is testing essentially a non-poetic activity?
I don’t think so. Yet, it doesn’t make sense to say “tests are poetry”. They aren’t. Then, what are they?