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Fwd: [Pharo-project] Smalltalk in Geneva, anyone?

by Stéphane Ducasse

Begin forwarded message: > From: Hilaire Fernandes <hilaire.fernandes(a)gmail.com> > Date: June 4, 2011 8:51:47 AM GMT+02:00 > To: pharo-project(a)lists.gforge.inria.fr > Subject: [Pharo-project] Smalltalk in Geneva, anyone? > Reply-To: Pharo-project(a)lists.gforge.inria.fr > > > -- > Education 0.2 -- http://blog.ofset.org/hilaire > >

June 4, 2011

Re: [Esug-list] Fwd: Re: Proposal for Mock Objects at ESUG 2011

by Simon Denier

On 2 juin 2011, at 21:53, stephane ducasse wrote: > tim send the code so that we can package it well. Yep I can do that, especially since I'm learning this kind of stuff these days. > > Stef > > > On May 29, 2011, at 2:31 PM, Tim Mackinnon wrote: > >> This has been an interesting thread - and it definitely seems that there is enough interested to warrant a further talk on the subject. I encourage Frank to pursue his idea to submit a talk (sadly I can't attend ESUG this year - which I am disappointed about. However maybe Frank and I can confer offline, and I can share some ideas) >> >> As Neil pointed out (and more for background info) - I did present the ideas behind Mocks (and the library SMock, that was written for Dolphin) - back in 2007. I also did an update at Smalltalks 2009 and used the following screencast - http://www.planningcards.com/Thoughts/SMock%20and%20TDD%20in%20action.htm. >> >> I have to confess that I keep promising to fully port SMock to Pharo/Squeak - and have done most of the work but I got a bit stuck with Monticello and how to properly do extension methods as well as getting diverted onto other things. It also felt that people weren't very interested in the technique so I was writing something more for myself and for researching how it would impact my Smalltalk coding experience. (By the way there is now much more documentation on how to use Monticello, and Pharo is so much better, and with our renewed energy in the UKSmalltalk meetings I'm more inspired to seek some help to get something checked in). It sounds like Frank also has another interesting library that we should compare (and since then I have augmented another internal Mock library on a JPMorgan project which approaches things in a slightly different manner). While SteveF mentioned that we can implement testing strategies in quite a small amount of Smalltalk code - the bulk of code actually comes in making test failures communicate clearly and explicitly as well as giving you a nice level of expression that keeps tests readable (I think these latter points are very important for long lasting, useful tests). >> >> Having said all of this - many of these conversations do indicated a slight misunderstanding of Mocks and where they came from. To fill in a bit of background: >> >> When I helped invent the approach it was very much driven from wanting to do TDD - and although it was originally written in Java it was inspired from my experience in Smalltalk. I am particularly fond of CRC cards - and the approach of "role-playing" objects and interactions (yet another Smalltalk invention). In our experiments with TDD in 1999, I found that our Java testing seemed "dumbed down - and we were often tempted to add "getter" methods to just test something. It seemed a far cry from Smalltalk and CRC - until we focused back on how to express that role play in our test code by not adding getter methods. Thus if you did take the time to CRC - and looked at who you collaborated with - then expressing that in a test became more interesting. "I am supposed to collaborate with the PayrollCalculator - and if its the end of the month then I should ask it to #calculatePensionFor: employee on: date for every employee in my dataset. If I get the wrong date, or don't ask about every employee then I should fail the test." We found that if you could focus on encoding the CRC session in your tests, that you got better tests and better code, as well as better test failures. In Java it felt like you got code that was more Smalltalk like. >> >> So I guess I would comment that for us, Mocks were different because we wanted to focus testing on asserting relationships and interactions and less on data values. I read all the literature at the time (there is a massive book on Testing on my bookshelf from that time) - and nothing else seemed to have this same focus (stubs felt more data related). As we played with this more and more, we refactored out useful techniques to ease the assertion of relationships, and someone coined the term "Needs driven development". That is, the act of thinking in this way made you want to have relationships that you could assert against. For me - these were the "interesting tests" that we had been writing back in Connextra that felt better than the others. >> >> I think this also came out of our experiences of using TDD - and the observation that when you write tests for objects that you consider low hanging fruit (because you know you need them, and they seem easy to test) - invariably you make the wrong decision and test that something threw an exception instead of returning a boolean (or better still in Smalltalk, has an ifAbsent: style construct). Of course you only find out about this when you go to plug your well tested object into the place where you need it and discover that if you had just returned true/false then it would be much easier to use. So you go back, rejig the tests and you get a bit further until you discover another slightly wonky decision. After doing this a few times I made a point of saying to my team mates, lets always start with the top most object and write tests that help us learn what these smaller pieces (which we know we need) should actually do. This resonated well with CRC and really brought everything together for us. This is how MockObjects were born (and I asked Steve and Nat if they would like a chapter in their GOOS book about this history - and they happily included it as an afterward at the back). >> >> So coming back to Smalltalk - I still would argue that this CRC technique is very much alive, and I personally still find that "Needs Driven Development" is a useful technique. However it does mean that you get into a chicken and egg situation. If you start testing with a high level object - how do you test or get something working when you are referring to things that don't yet exist? For me, thats where Mocks step in - they are intended to be light weight proxies for things that don't yet exist. You do a CRC session, pick out the highest level object you can - code it (with tests) and mock out the relationships that you recorded on your CRC cards. As you are coding it, you will probably change your mind (writing real code has a way of doing that) - and you modify your lightweight relationship assertions (mocks). This also works best and is easier if you delegate responsibility and avoid returning complicated things (its easier to Mock and happily conforms to the law of Demeter). >> >> When you are happy enough with your top level object - you can then pick on one of those other relationships, and your tests should now show you the "Protocol" that this new object should have. So you create it - and repeat the process. The interesting twist that the screencast I linked to demonstrates - is that in Smalltalk (and indeed in Ruby or Python) we can create MockObjects that don't have any code, however you can use all those assertions to actually generate an object ready for you to test it. I think this is an interesting idea that needs more research (I feel that the right assertions could generate interesting code). >> >> As a final observation - when people talk about TestDoubles and MethodWrappers, I think they are missing the point of mocks as I intended them - as you can't double or wrap something that isn't yet written? So I would say that these techniques are perhaps better suited to code that is already in existence. Of course once you have done TDD with Mocks, and written your code you are then in a place where you can decide what to do? For me - I have kept the mocks in place - however I think in Smalltalk there is possibly a useful "Lint" check that makes sure your mock stays in sync with the underlying code (I haven't written any Slime style rules - but I think it would be interesting). There is also a useful hybrid functionality where you only mock certain methods and pass control to a real object underneath - or "method wrap" and decorate assertions you want on existing methods and pass down to the functionality underneath. I would argue that these are possibly more "maintenance" or "integration" style endeavours - and it would be a shame to not use the purer "Needs driven development" style when you can. >> >> Anyway - I hope this is a useful background and might inspire more work in the area. >> >> Tim >> >> >> _______________________________________________ >> Esug-list mailing list >> Esug-list(a)lists.esug.org >> http://lists.esug.org/mailman/listinfo/esug-list_lists.esug.org > > > _______________________________________________ > Esug-list mailing list > Esug-list(a)lists.esug.org > http://lists.esug.org/mailman/listinfo/esug-list_lists.esug.org -- Simon Denier

June 3, 2011

Re: [Esug-list] Fwd: Re: Proposal for Mock Objects at ESUG 2011

by stephane ducasse

tim send the code so that we can package it well. Stef On May 29, 2011, at 2:31 PM, Tim Mackinnon wrote: > This has been an interesting thread - and it definitely seems that there is enough interested to warrant a further talk on the subject. I encourage Frank to pursue his idea to submit a talk (sadly I can't attend ESUG this year - which I am disappointed about. However maybe Frank and I can confer offline, and I can share some ideas) > > As Neil pointed out (and more for background info) - I did present the ideas behind Mocks (and the library SMock, that was written for Dolphin) - back in 2007. I also did an update at Smalltalks 2009 and used the following screencast - http://www.planningcards.com/Thoughts/SMock%20and%20TDD%20in%20action.htm. > > I have to confess that I keep promising to fully port SMock to Pharo/Squeak - and have done most of the work but I got a bit stuck with Monticello and how to properly do extension methods as well as getting diverted onto other things. It also felt that people weren't very interested in the technique so I was writing something more for myself and for researching how it would impact my Smalltalk coding experience. (By the way there is now much more documentation on how to use Monticello, and Pharo is so much better, and with our renewed energy in the UKSmalltalk meetings I'm more inspired to seek some help to get something checked in). It sounds like Frank also has another interesting library that we should compare (and since then I have augmented another internal Mock library on a JPMorgan project which approaches things in a slightly different manner). While SteveF mentioned that we can implement testing strategies in quite a small amount of Smalltalk code - the bulk of code actually comes in making test failures communicate clearly and explicitly as well as giving you a nice level of expression that keeps tests readable (I think these latter points are very important for long lasting, useful tests). > > Having said all of this - many of these conversations do indicated a slight misunderstanding of Mocks and where they came from. To fill in a bit of background: > > When I helped invent the approach it was very much driven from wanting to do TDD - and although it was originally written in Java it was inspired from my experience in Smalltalk. I am particularly fond of CRC cards - and the approach of "role-playing" objects and interactions (yet another Smalltalk invention). In our experiments with TDD in 1999, I found that our Java testing seemed "dumbed down - and we were often tempted to add "getter" methods to just test something. It seemed a far cry from Smalltalk and CRC - until we focused back on how to express that role play in our test code by not adding getter methods. Thus if you did take the time to CRC - and looked at who you collaborated with - then expressing that in a test became more interesting. "I am supposed to collaborate with the PayrollCalculator - and if its the end of the month then I should ask it to #calculatePensionFor: employee on: date for every employee in my dataset. If I get the wrong date, or don't ask about every employee then I should fail the test." We found that if you could focus on encoding the CRC session in your tests, that you got better tests and better code, as well as better test failures. In Java it felt like you got code that was more Smalltalk like. > > So I guess I would comment that for us, Mocks were different because we wanted to focus testing on asserting relationships and interactions and less on data values. I read all the literature at the time (there is a massive book on Testing on my bookshelf from that time) - and nothing else seemed to have this same focus (stubs felt more data related). As we played with this more and more, we refactored out useful techniques to ease the assertion of relationships, and someone coined the term "Needs driven development". That is, the act of thinking in this way made you want to have relationships that you could assert against. For me - these were the "interesting tests" that we had been writing back in Connextra that felt better than the others. > > I think this also came out of our experiences of using TDD - and the observation that when you write tests for objects that you consider low hanging fruit (because you know you need them, and they seem easy to test) - invariably you make the wrong decision and test that something threw an exception instead of returning a boolean (or better still in Smalltalk, has an ifAbsent: style construct). Of course you only find out about this when you go to plug your well tested object into the place where you need it and discover that if you had just returned true/false then it would be much easier to use. So you go back, rejig the tests and you get a bit further until you discover another slightly wonky decision. After doing this a few times I made a point of saying to my team mates, lets always start with the top most object and write tests that help us learn what these smaller pieces (which we know we need) should actually do. This resonated well with CRC and really brought everything together for us. This is how MockObjects were born (and I asked Steve and Nat if they would like a chapter in their GOOS book about this history - and they happily included it as an afterward at the back). > > So coming back to Smalltalk - I still would argue that this CRC technique is very much alive, and I personally still find that "Needs Driven Development" is a useful technique. However it does mean that you get into a chicken and egg situation. If you start testing with a high level object - how do you test or get something working when you are referring to things that don't yet exist? For me, thats where Mocks step in - they are intended to be light weight proxies for things that don't yet exist. You do a CRC session, pick out the highest level object you can - code it (with tests) and mock out the relationships that you recorded on your CRC cards. As you are coding it, you will probably change your mind (writing real code has a way of doing that) - and you modify your lightweight relationship assertions (mocks). This also works best and is easier if you delegate responsibility and avoid returning complicated things (its easier to Mock and happily conforms to the law of Demeter). > > When you are happy enough with your top level object - you can then pick on one of those other relationships, and your tests should now show you the "Protocol" that this new object should have. So you create it - and repeat the process. The interesting twist that the screencast I linked to demonstrates - is that in Smalltalk (and indeed in Ruby or Python) we can create MockObjects that don't have any code, however you can use all those assertions to actually generate an object ready for you to test it. I think this is an interesting idea that needs more research (I feel that the right assertions could generate interesting code). > > As a final observation - when people talk about TestDoubles and MethodWrappers, I think they are missing the point of mocks as I intended them - as you can't double or wrap something that isn't yet written? So I would say that these techniques are perhaps better suited to code that is already in existence. Of course once you have done TDD with Mocks, and written your code you are then in a place where you can decide what to do? For me - I have kept the mocks in place - however I think in Smalltalk there is possibly a useful "Lint" check that makes sure your mock stays in sync with the underlying code (I haven't written any Slime style rules - but I think it would be interesting). There is also a useful hybrid functionality where you only mock certain methods and pass control to a real object underneath - or "method wrap" and decorate assertions you want on existing methods and pass down to the functionality underneath. I would argue that these are possibly more "maintenance" or "integration" style endeavours - and it would be a shame to not use the purer "Needs driven development" style when you can. > > Anyway - I hope this is a useful background and might inspire more work in the area. > > Tim > > > _______________________________________________ > Esug-list mailing list > Esug-list(a)lists.esug.org > http://lists.esug.org/mailman/listinfo/esug-list_lists.esug.org

June 2, 2011

Re: [Esug-list] Fwd: Re: Proposal for Mock Objects at ESUG 2011

by Dennis Schetinin

I read your message after I've posted my attempt to explain ideas behind mocks. Now I see there were no need for that. :) Very good and clear, just great explanation! 2011/5/29 Tim Mackinnon <macta(a)pobox.com> > This has been an interesting thread - and it definitely seems that there is > enough interested to warrant a further talk on the subject. I encourage > Frank to pursue his idea to submit a talk (sadly I can't attend ESUG this > year - which I am disappointed about. However maybe Frank and I can confer > offline, and I can share some ideas) > > As Neil pointed out (and more for background info) - I did present the > ideas behind Mocks (and the library SMock, that was written for Dolphin) - > back in 2007. I also did an update at Smalltalks 2009 and used the following > screencast - > http://www.planningcards.com/Thoughts/SMock%20and%20TDD%20in%20action.htm. > > I have to confess that I keep promising to fully port SMock to Pharo/Squeak > - and have done most of the work but I got a bit stuck with Monticello and > how to properly do extension methods as well as getting diverted onto other > things. It also felt that people weren't very interested in the technique so > I was writing something more for myself and for researching how it would > impact my Smalltalk coding experience. (By the way there is now much more > documentation on how to use Monticello, and Pharo is so much better, and > with our renewed energy in the UKSmalltalk meetings I'm more inspired to > seek some help to get something checked in). It sounds like Frank also has > another interesting library that we should compare (and since then I have > augmented another internal Mock library on a JPMorgan project which > approaches things in a slightly different manner). While SteveF mentioned > that we can implement testing strategies in quite a small amount of > Smalltalk code - the bulk of code actually comes in making test failures > communicate clearly and explicitly as well as giving you a nice level of > expression that keeps tests readable (I think these latter points are very > important for long lasting, useful tests). > > Having said all of this - many of these conversations do indicated a slight > misunderstanding of Mocks and where they came from. To fill in a bit of > background: > > When I helped invent the approach it was very much driven from wanting to > do TDD - and although it was originally written in Java it was inspired from > my experience in Smalltalk. I am particularly fond of CRC cards - and the > approach of "role-playing" objects and interactions (yet another Smalltalk > invention). In our experiments with TDD in 1999, I found that our Java > testing seemed "dumbed down - and we were often tempted to add "getter" > methods to just test something. It seemed a far cry from Smalltalk and CRC - > until we focused back on how to express that role play in our test code by > not adding getter methods. Thus if you did take the time to CRC - and looked > at who you collaborated with - then expressing that in a test became more > interesting. "I am supposed to collaborate with the PayrollCalculator - and > if its the end of the month then I should ask it to #calculatePensionFor: > employee on: date for every employee in my dataset. If I get the wrong > date, or don't ask about every employee then I should fail the test." We > found that if you could focus on encoding the CRC session in your tests, > that you got better tests and better code, as well as better test failures. > In Java it felt like you got code that was more Smalltalk like. > > So I guess I would comment that for us, Mocks were different because we > wanted to focus testing on asserting relationships and interactions and less > on data values. I read all the literature at the time (there is a massive > book on Testing on my bookshelf from that time) - and nothing else seemed to > have this same focus (stubs felt more data related). As we played with this > more and more, we refactored out useful techniques to ease the assertion of > relationships, and someone coined the term "Needs driven development". That > is, the act of thinking in this way made you want to have relationships that > you could assert against. For me - these were the "interesting tests" that > we had been writing back in Connextra that felt better than the others. > > I think this also came out of our experiences of using TDD - and the > observation that when you write tests for objects that you consider low > hanging fruit (because you know you need them, and they seem easy to test) - > invariably you make the wrong decision and test that something threw an > exception instead of returning a boolean (or better still in Smalltalk, has > an ifAbsent: style construct). Of course you only find out about this when > you go to plug your well tested object into the place where you need it and > discover that if you had just returned true/false then it would be much > easier to use. So you go back, rejig the tests and you get a bit further > until you discover another slightly wonky decision. After doing this a few > times I made a point of saying to my team mates, lets always start with the > top most object and write tests that help us learn what these smaller pieces > (which we know we need) should actually do. This resonated well with CRC and > really brought everything together for us. This is how MockObjects were born > (and I asked Steve and Nat if they would like a chapter in their GOOS book > about this history - and they happily included it as an afterward at the > back). > > So coming back to Smalltalk - I still would argue that this CRC technique > is very much alive, and I personally still find that "Needs Driven > Development" is a useful technique. However it does mean that you get into a > chicken and egg situation. If you start testing with a high level object - > how do you test or get something working when you are referring to things > that don't yet exist? For me, thats where Mocks step in - they are intended > to be light weight proxies for things that don't yet exist. You do a CRC > session, pick out the highest level object you can - code it (with tests) > and mock out the relationships that you recorded on your CRC cards. As you > are coding it, you will probably change your mind (writing real code has a > way of doing that) - and you modify your lightweight relationship assertions > (mocks). This also works best and is easier if you delegate responsibility > and avoid returning complicated things (its easier to Mock and happily > conforms to the law of Demeter). > > When you are happy enough with your top level object - you can then pick on > one of those other relationships, and your tests should now show you the > "Protocol" that this new object should have. So you create it - and repeat > the process. The interesting twist that the screencast I linked to > demonstrates - is that in Smalltalk (and indeed in Ruby or Python) we can > create MockObjects that don't have any code, however you can use all those > assertions to actually generate an object ready for you to test it. I think > this is an interesting idea that needs more research (I feel that the right > assertions could generate interesting code). > > As a final observation - when people talk about TestDoubles and > MethodWrappers, I think they are missing the point of mocks as I intended > them - as you can't double or wrap something that isn't yet written? So I > would say that these techniques are perhaps better suited to code that is > already in existence. Of course once you have done TDD with Mocks, and > written your code you are then in a place where you can decide what to do? > For me - I have kept the mocks in place - however I think in Smalltalk there > is possibly a useful "Lint" check that makes sure your mock stays in sync > with the underlying code (I haven't written any Slime style rules - but I > think it would be interesting). There is also a useful hybrid functionality > where you only mock certain methods and pass control to a real object > underneath - or "method wrap" and decorate assertions you want on existing > methods and pass down to the functionality underneath. I would argue that > these are possibly more "maintenance" or "integration" style endeavours - > and it would be a shame to not use the purer "Needs driven development" > style when you can. > > Anyway - I hope this is a useful background and might inspire more work in > the area. > > Tim > > > _______________________________________________ > Esug-list mailing list > Esug-list(a)lists.esug.org > http://lists.esug.org/mailman/listinfo/esug-list_lists.esug.org > -- Dennis Schetinin

June 2, 2011

Re: [Esug-list] ESUG SummerTalk - Fuel, binary object serializer

by Yoshiki Ohshima

At Tue, 31 May 2011 23:16:12 +0200, Mariano Martinez Peck wrote: > > On Sun, May 29, 2011 at 9:07 PM, Yoshiki Ohshima <yoshiki(a)vpri.org> wrote: > > At Sun, 29 May 2011 20:52:45 +0200, > Mariano Martinez Peck wrote: > > > > On Sun, May 29, 2011 at 8:45 PM, Yoshiki Ohshima <yoshiki(a)vpri.org> wrote: > > > > At Sat, 28 May 2011 09:33:27 +0200, > > Stéphane Ducasse wrote: > > > > > > Yoshiki > > > > > > if you want to help testing, improving fuel you are welcome. > > > The idea is to make it fast fast fast without vm support. > > > > Yeah. The reason for example I went to pad data to 4 bytes > > > > What do you mean by padding data to 4 bytes? I don't understand :( > > Say a string has length of 5 ('abcde'), the data in file for it > would be "97 98 99 100 101 0 0 0". > > Sorry but I don't understand then how that is related to "The reason for example I went to pad data to 4 bytes was that > there may be a clever trick I may be able to do to read data into > arrays "directly" and stuff, but did not get around implementing it." > > > > was that > > there may be a clever trick I may be able to do to read data into > > arrays "directly" and stuff, > > > > what do you mean by that? like ImageSegment does? I mean, include also object headers in the stream and then avoid to recreate objects (using #basicNew) ? > > Not like ImageSegment, but more like #hackBits: reading from file > into a string object of right size. > > I am not sure if I understand. For some kind of objects (those that are variable) we store first its size and then at materialization time we directly create an object > of that size using #basicNew: > > but I guess you are talking about something else. Hmm, I'm also confused. You know that ByteStrings are padded in the image, right? And you see a user of #hackBits:, #nextWordsInto:, right? We can eliminate some buffer copying there. For example, when I run Fuel materializer, I see PositionableStream>>nextString is used which does not do basicNew: of (Byte)String but actually does extra copy (which can be easily eliminated and would make it faster). -- Yoshiki

June 1, 2011

Re: [Esug-list] Proposal for Mock Objects at ESUG 2011

by Frank Shearar

2011/5/31 Göran Krampe <goran(a)krampe.se>: > On 05/31/2011 04:59 PM, Frank Shearar wrote: >> >> 2011/5/31 Göran Krampe<goran(a)krampe.se>: >>> >>> So refreshingly to see someone that *also* notes that testing using mocks >>> actually break encapsulation. Thank you, thank you... >> >> Or to rephrase, "documenting the precise nature of the colloboration >> between an object and its context documents that precise nature." >> >> In Colin's example, Set's collaboration with Array is purely an >> implementation detail and, as he notes, testing the implementation - >> whether checking that Set stores the value in the array, or what >> messages Set might send to Array - hurts you. >> >> I fail to see how that makes mocks bad. Unless you're railing against >> hype? In which case, I agree: there ain't no such thing as a free >> lunch, there is no silver bullet, etc etc. > > Well, yes, railing against hype. But also railing against writing tests that > work from "the inside" by using mocks. It is of course a matter of taste, > style and in the end weighing pros and cons. But I have seen too much use of > mocks that end up making the tests purely mirror the implementation - so > even the slightest internal modification would break the test. PragProg were kind enough to publish a very well-timed article: http://pragprog.com/magazines/2011-06/practical-mock-advice The punchline? "Generally, there is one overarching reason for why you would use a mock. That reason is this: You care about an implementation detail in your code. And when do you care? You care when it drives behavior." frank

June 1, 2011

Re: [Esug-list] Proposal for Mock Objects at ESUG 2011

by Göran Krampe

On 05/31/2011 04:59 PM, Frank Shearar wrote: > 2011/5/31 Göran Krampe<goran(a)krampe.se>: >> So refreshingly to see someone that *also* notes that testing using mocks >> actually break encapsulation. Thank you, thank you... > > Or to rephrase, "documenting the precise nature of the colloboration > between an object and its context documents that precise nature." > > In Colin's example, Set's collaboration with Array is purely an > implementation detail and, as he notes, testing the implementation - > whether checking that Set stores the value in the array, or what > messages Set might send to Array - hurts you. > > I fail to see how that makes mocks bad. Unless you're railing against > hype? In which case, I agree: there ain't no such thing as a free > lunch, there is no silver bullet, etc etc. Well, yes, railing against hype. But also railing against writing tests that work from "the inside" by using mocks. It is of course a matter of taste, style and in the end weighing pros and cons. But I have seen too much use of mocks that end up making the tests purely mirror the implementation - so even the slightest internal modification would break the test. regards, Göran

May 31, 2011

Re: [Esug-list] ESUG SummerTalk - Fuel, binary object serializer

by Mariano Martinez Peck

On Sun, May 29, 2011 at 9:07 PM, Yoshiki Ohshima <yoshiki(a)vpri.org> wrote: > At Sun, 29 May 2011 20:52:45 +0200, > Mariano Martinez Peck wrote: > > > > On Sun, May 29, 2011 at 8:45 PM, Yoshiki Ohshima <yoshiki(a)vpri.org> > wrote: > > > > At Sat, 28 May 2011 09:33:27 +0200, > > Stéphane Ducasse wrote: > > > > > > Yoshiki > > > > > > if you want to help testing, improving fuel you are welcome. > > > The idea is to make it fast fast fast without vm support. > > > > Yeah. The reason for example I went to pad data to 4 bytes > > > > What do you mean by padding data to 4 bytes? I don't understand :( > > Say a string has length of 5 ('abcde'), the data in file for it > would be "97 98 99 100 101 0 0 0". > > Sorry but I don't understand then how that is related to "The reason for example I went to pad data to 4 bytes was that there may be a clever trick I may be able to do to read data into arrays "directly" and stuff, but did not get around implementing it." > > was that > > there may be a clever trick I may be able to do to read data into > > arrays "directly" and stuff, > > > > what do you mean by that? like ImageSegment does? I mean, include also > object headers in the stream and then avoid to recreate objects (using > #basicNew) ? > > Not like ImageSegment, but more like #hackBits: reading from file > into a string object of right size. I am not sure if I understand. For some kind of objects (those that are variable) we store first its size and then at materialization time we directly create an object of that size using #basicNew: but I guess you are talking about something else. > For pointer arrays and actual > literal fields, I am not sure I can apply this however. > > I would not put object headers, as you would agree^^; > > -- Yoshiki > -- Mariano http://marianopeck.wordpress.com

May 31, 2011

Re: [Esug-list] Proposal for Mock Objects at ESUG 2011

by Dennis Schetinin

First of all, I'm sorry for my English. (And I'll appreciate it very much if someone will point to mistakes of any kind in the following text.) I attempted to analyze and structure comments, questions and ideas presented in the thread and I think I found one thing that can be a starting point for the discussion (despite the fact the discussion already started… away back). I've got a strong feeling (I've got it several years ago and had a number of evidences, including several in this thread) that there are (at least) two very different (if not opposite) points of view on mock objects… and it seems to me, the root of this divergence is even deeper and more general — understanding of TDD. So, I think I have to explain my point of view. (Telling "my" here I claim to be an author of all errors, misinterpretations and nonsenses I'll present. But all the good, reasonable and interesting things were invented by other (clever) people.) So, why and how did I dare to claim TDD is not really popular among Smalltalkers? Because I still believe tests can drive (nearly) all stages of development: not just coding, but also design and even analysis (at least to clarify and formalize results of analysis). But I rarely (if ever) see any artifacts (tests of the kind). Perhaps I'm wrong, but most of the tests I saw were more "acceptance" tests, perhaps even written afterwards. Once again: very likely I'm wrong (and I'll be glad to be, actually). Why is it important for me to use TDD? Because, as a bad programmer, I need a help. I have a lot of things I must think about during development (won't enumerate, we all know them), so I want a tool that helps me not to think too much — at least, at the points where it is possible at all. (If I misinterpret the word "driving" here, please let me know.) Thus, if I write a line of code that is not directly(!) driven by a test, I don't TDD. If I make some up-front design I'm not actually test-driven. Even, if I simply go few steps designing top-down without tests at a very small single stage of development, TDD is broken. If you think it is too extreme and strict — ok, let's talk about "seamless TDD" vs., say, "partial TDD". (Yes, I know about steps of variable size during TDD etc. But I still think it's a bit another thing. Let's judge a bit later…) So, considering an example by Colin Putney: | set | set := Set new. set add: 3. self assert: (set includes: 3). vs | set | mock := MockArray new: 5 mock expect: (Message selector: #at:put: arguments: #(4 3)). set := Set withArray: mock. set add: 3. Isn't it obvious mocking array here is an overkill and the first test is better? For sure it is. But why? Because there's actually no development in the 1st test. Otherwise, what is it for: #add: or #includes:? Which feature this test makes me to add to the system-under-test (the Set)? I must select, I must think, thus I'm not driven by the test. Consider also (slightly) another issue: here we have a ready-to-use inner collection for the Set. But if I have no yet? Isn't it a common and very frequent situation during development: I have to implement a (sub)system that comprises several objects working together? (I think I don't have to provide examples here to prove.) Which one should I implement first? I don't know, I have to explore. I must analyze the system, i.e. divide it into subcomponents, find the ones independent and start by implementing them first. But what is this process, I've just described? It's a top-down up-front design. Is it test-driven? Obviously, no. Do I have an alternative? Yes, I can use mocks. With Mocketry I could write: SetTests >> testStoresElementsInInnerCollection [:collection | set := Set withArray: collection. [set add: #element] should strictly satisfy: [collection add: #element]] runScenario Of course, this is a very early step of development, as I'll have to implement an efficient algorithm to check, if element exists in the set before adding it… And with mocks it is very likely I'll be driven to implement it as a pluggable object. Probably, this can make Set a bit more flexible, doesn't it? On the other hand, it can introduce unnecessary complexity. Apparently, this is a good example to explore it further… While I must admit technique of mock object is not a silver bullet, and must be used carefully… just as any other tool. So… Conclusion 1: Yes, mock objects is a specific tool for specific situations. But as for me, I meet these specific situation almost as frequently, as other, non-specific(?) circumstances. Conclusion 2: I think mocks should be used, first of all, to discover different aspects of functionality and distribute it among various objects. (Documentation, optimization, etc. goes later… if goes at all…) When I start to work on a new feature, I first try to write an acceptance test. But I never can implement it 'as is'. And I hate to leave it red or mark it as ignored (in any way). So I try to transform it into something I can implement easily and fast. And often this leads me to a test with mocks. This make me to divide complex functionality into smaller blocks and factor them out to collaborators. The trick is to make those objects to behave (one-by-one and altogether)… But that's another (and big) topic. -- Dennis Schetinin

May 31, 2011

Re: [Esug-list] Proposal for Mock Objects at ESUG 2011

by Frank Shearar

2011/5/31 Göran Krampe <goran(a)krampe.se>: > Hey! > > Stumbled into this thread but just HAVE to respond... Snipping heavily here: > > On 05/27/2011 11:11 PM, Colin Putney wrote: >> >> without them. It's just *mocks* that are mostly unnecessary. > > Amen! I have been thinking the rest of the world had gone mad... > >> Personally, I find that mocks are *very* useful in a few very specific >> situations, but they can cause problems it other situations. They're >> like a very specialized tool - invaluable when you need it, but kept >> in the bottom of the toolbox and not used very often. > > Right. > > [SNIP of good stuff] >> >> I know that BDD folks like to talk about testing behaviour rather than >> state, but I don't find the distinction useful. Testing state breaks >> the encapsulation of the objects under test, and couples the test too >> closely to their internal implementation. Testing behaviour using >> mocks *does the same thing*; it just restricts the implementation in a >> different way. > > So refreshingly to see someone that *also* notes that testing using mocks > actually break encapsulation. Thank you, thank you... Or to rephrase, "documenting the precise nature of the colloboration between an object and its context documents that precise nature." In Colin's example, Set's collaboration with Array is purely an implementation detail and, as he notes, testing the implementation - whether checking that Set stores the value in the array, or what messages Set might send to Array - hurts you. I fail to see how that makes mocks bad. Unless you're railing against hype? In which case, I agree: there ain't no such thing as a free lunch, there is no silver bullet, etc etc. frank

May 31, 2011