I am attempting to convince my colleagues to start using a build server and automated building for our Silverlight application. I have justified it on the grounds that we will catch integration errors more quickly, and will also always have a working dev copy of the system with the latest changes. But some still don't get it.
What are the most significant advantages of using a Build Server for your project?
There are more advantages than just finding compile errors earlier (which is significant):
Produce a full clean build for each check-in (or daily or however it's configured)
Produce consistent builds that are less likely to have just worked due to left-over artifacts from a previous build
Provide a history of which change actually broke a build
Provide a good mechanism for automating other related processes (like deploy to test computers)
Continuous integration reveals any problems in the big picture, as different teams/developers work in different parts of the code/application/system
Unit and integration tests ran with the each build go even deeper and expose problems that would maybe not be seen on the developer's workstation
Free coffees/candy/beer. When someone breaks the build, he/she makes it up for the other team members...
I think if you can convince your team members that there WILL be errors and integration problems that are not exposed during the development time, that should be enough.
And of course, you can tell them that the team will look ancient in the modern world if you don't run continuous builds :)
See Continuous Integration: Benefits of Continuous Integration :
On the whole I think the greatest and most wide ranging benefit of Continuous Integration is reduced risk. My mind still floats back to that early software project I mentioned in my first paragraph. There they were at the end (they hoped) of a long project, yet with no real idea of how long it would be before they were done.
...
As a result projects with Continuous Integration tend to have dramatically less bugs, both in production and in process. However I should stress that the degree of this benefit is directly tied to how good your test suite is. You should find that it's not too difficult to build a test suite that makes a noticeable difference. Usually, however, it takes a while before a team really gets to the low level of bugs that they have the potential to reach. Getting there means constantly working on and improving your tests.
If you have continuous integration, it removes one of the biggest barriers to frequent deployment. Frequent deployment is valuable because it allows your users to get new features more rapidly, to give more rapid feedback on those features, and generally become more collaborative in the development cycle. This helps break down the barriers between customers and development - barriers which I believe are the biggest barriers to successful software development.
From my personal experience, setting up a build server and implementing CI process, really changes the way the project is conducted. The act of producing a build becomes an uneventful everyday thing, because you literally do it every day. This allows you to catch things earlier and be more agile.
Also note that setting build server is only a part of the CI process, which includes setting up tests and ultimately automating the deployment (very useful).
Another side-effect benefit that often doen't get mentioned is that CI tools like CruiseControl.NET becomes the central issuer of all version numbers for all branches, including internal RCs. You could then enforce your team to always ship a build that came out of the CI tool, even if it's a custom version of the product.
Early warning of broken or incompatible code means that all conflicts are identified asap, thereby avoiding last minute chaos on the release date.
When your boss says "I need a copy of the latest code ASAP" you can get it to them in < 5 minutes.
You can make the build available to internal testers easily, and when they report a bug they can easily tell you "it was the April 01 nightly build" so that you can work with the same version of the source code.
You'll be sure that you have an automated way to build the code that doesn't rely on libraries / environment variables / scripts / etc. that are set up in developers' environments but hard to replicate by others who want to work with the code.
We have found the automatic VCS tagging of the exact code that produce a version very helpful in going back to a specific version to replicate an issue.
Integration is a blind spot
Integration often doesn't get any respect - "we just throw the binaries into an installer thingie". If ithis doesn't work, it's the installers fault.
Stable Build Environment
Prevents excuses such as "This error sometimes occurs when built on Joe's machine". Prevents using old dependent libraries accidentally when building on Mikes machine.
True dogfooding
You inhouse testers and users have a true customer experience. Your developers have a clear reference for reproducing errors.
My manager told us we needed to set them up for two major reasons. None were really to do with the final project but to make sure what is checked in or worked on is correct.
First to clean up DLL Hell. When someone builds on their local machine they can be pointing at any reference folder. Lots of projects were getting built with the wrong versions of dlls from someone not updating their local folder. In the build server it will always be built of the same source. All you have to do is get latest to get the latest references.
The second major thing for us was a way to support projects with little knowledge of them. Any developer can go grab the source and do a minor fix if required. They don't have to mess with hours of set up or finding references. We have an overseas team that works primarily on a project but if there is a rush fix we need to do during US hours we can grab latest and be able to build not have to worry about broken source or what didn't get checked in. Gated checkins save everyone else on your team time.
Related
Our development team (about 40 developers) has a formal build every two weeks. We have a process that in the "build day", every developers are forbiden to commit code into SVN. I don't think this is a good idea because:
Build will take days (even weeks in bad time) to make and BVT.
People couldn't commit code as they will, they will not work.
People will commit all codes in a huge pack, so the common is hard to write.
I want know if your team has same policy, and if not how do you take this situation.
Thanks
Pick a revision.
Check out the code from that revision.
Build.
???
Profit.
Normally, a build is made from a labeled code.
If the label is defined (and do not move), every developer can commit as much as he/she wants: the build will go on from a fixed and defined set of code.
If fixes need to be make on that set of code being built, a branch can then be defined from that label, minor fixes can be made to achieve a correct build, before being merging back to the current development branch.
A "development effort" (like a build with its tweaks) should not ever block another development effort (the daily commits).
Step 1: svn copy /trunk/your/project/goes/here /temp/build
Step 2: Massage your sources in /temp/build
Step 3: Perform the build in /temp/build. If you encounter errors, fix them in /temp/build and build again
Step 4: If successful, svn move /temp/build /builds/product/buildnumber
This way, developers can check in whenever they want and are not disturbed by the daily/weekly/monthly/yearly build
Sounds frustrating. Is there a reason you guys are not doing Continuous Integration?
If that sounds too extreme for you, then definitely invest some time in learning how branching works in SVN. I think you could convince the team to either develop on branches and merge into trunk, or else commit the "formal build" to a particular tag/branch.
We create a branch for every ticket or new feature, even if the ticket is small (eg takes only 2 hours to fix).
At the end of each the coding part of each iteration we decide what tickets to include in the next release. We then merge those tickets into trunk and release software.
There are other steps within that process where testing is performed by another developer on each ticket branch before the ticket is merged to trunk.
Developers can always code by creating their own branch from trunk at any time. Note we are a small team with only 12 developers.
Both Kevin and VonC have well pointed out that the build should be made from a specific revision of the code and should not ever block the developers from committing in new code. If this is somehow a problem, then you should consider using another version management software which uses centralized AND local repositories. For example, in mercurial, there is a central repository just like in svn, but developers also have a local repository. This means that when a developer makes a commit, he only commits to his local repository and the changes will not be seen by other developers. Once he is ready to commit the code for other developers, then the developer just pushes the changes from his local repository to the centralized repository.
The advantage with this kind of an approach is that developers can commit smaller pieces of code, even if it would break a build, because the changes are only applied to the local repository. Once the changes are stable enough, they can be pushed to the centralized repository. This way a developer can have the advatange of source control even though the centralized repository would be down.
Oh, and you'll be looking at branches in a whole new way.
If you became interested in mercurial, check out this site: http://hginit.com
I have worked on projects with a similar policy. The reason we needed such a policy is that we were not using branches. If developers are allowed to create a branch, then they can make whatever commits they need to on that branch and not interrupt anyone else -- the policy becomes "don't merge to main" during the weekly-build period.
Another approach is to have the weekly-build split off onto a branch, so that regardless of what gets checked in (and possibly merged), the weekly build will not be affected.
Using labels, as VonC suggested, is also a good approach. However, you need to consider what happens when a labeled file needs a patch for the nightly build -- what if a developer has checked in a change to that file since it was labeled, and that developer's changes should not be included in the weekly build? In that case, you will need a branch anyway. But branching off a label can be a good approach too.
I have also worked on projects that make branches like crazy and it becomes a mess trying to figure out what's happening with any particular file. Changes may be committed to multiple branches in the same timeframe. Eventually the merge conflicts need to be resolved. This can be quite a headache. Regardless, my preference is to be able to use branches.
Wow, thats an awful way to develop.
Last time I worked in a really large team we had about 100 devs in 3 time zones: USA, UK, India, so we could effectively have 24 hour development.
Each dev would check the build tree and work on what they had to work on.
At the same time, there would be continuous builds happening. The build would make its copy from the submitted code and build it. Any failures would go back to the most recent submitter(s) for code for that build.
Result:
Lots of builds, most of which compiled OK. These builds then started automatic smoke testing scenarios to find any unexpected bugs not found during testing priot to commiting.
Build failures found early, fixed early.
Bugs found early, fixed early.
Developers only wait the minimum time to submit (they have to wait until any other dev that is submitting has finished submitting - this requirement made so that the build servers have a point at which they can grab the source tree for a new build).
Most devs had two machines so they could work on a second bug while running their tests on the other machine (the tests were very graphical and would cause all sorts of focus issues, so you really needed a different machine to do other work).
Highly productive, continuous development with no deadtime as in your scenario.
To be fair, I don't think I could work in place that you describe. It would be soul destroying to work in such an unproductive way.
I strongly believe that your organization would benefit from Continuous Integrations, where you build very often, perhaps for every checkin to your code base.
Don't know if i'll get shot for saying this, but you should really move to a decentralized solution like GIT. SVN is horrible about this and the fact that you can't commit basically stops people from working properly. At 40 people this is worth it because each can continue working on their own stuff and only push what they want. The build server can do what it wants and build without affecting everyone.
Yet another example why Linus was right when saying that in almost all cases, a decentralized solution like git works best in real life teams.
We have 4 different environments:
Staging
Dev
User Acceptance
Live
We use TFS, pull down the latest code and code away.
When they finish a feature, the developers individually upload their changes to Staging. If the site is stable (determined by really loose testing), we upload changes to Dev, then UserAcceptance and then live.
We are not using builds/tags in our source control at all.
What should I tell management? They don't seem to think there is an issue as far as I can tell.
If it would be good for you, you could become the Continuous Integration champion of your company. You could do some research on a good process for CI with TFS, write up a proposed solution, evangelize it to your fellow developers and direct managers, revise it with their input and pitch it to management. Or you could just sit there and do nothing.
I've been in management for a long time. I always appreciate someone who identifies an issue and proposes a well thought-out solution.
Whose management? And how far removed are they from you?
I.e. If you are just a pleb developer and your managers are the senior developers then find another job. If you are a Senior developer and your managers are the CIO types, i.e. actually running the business... then it is your job to change it.
Tell them that if you were using a key feature of very expensive software they spent a lot of money on, it would be trivial to tell what code got pushed out when. That would mean in the event of a subtle bug getting introduced that gets passed user acceptance testing, it would be a matter of diffing the two versions to figure out what changed.
One of the most important parts of using TAGS is so you can rollback to a specific point in time. Think of it as an image backup. If something bad gets deployed you can safely assume you can "roll" back to a previous working version.
Also, developers can quickly grab a TAG (dev, prod or whatever) and deploy to their development PC...a feature I use all the time to debug production problems.
So you need someone to tell the other developers that they must label their code every time a build is done and increment a version counter. Why can't you do that?
You also need to tell management that you believe the level of testing done is not sufficient. This is not a unique problem for an organisation and they'll probably say they already know. No harm in mentioning it though rather than waiting for a major problem to arrive.
As far as individuals doing builds or automated build processes this depends on whether you really need this based on how many developers there are and how often you do builds.
What is the problem? As you said, you can't tell if management see the problem. Perhaps they don't! Tell them what you see as the current problem and what you would recommend to fix the problem. The problem has to of the nature of "our current process has failed 3 out of 10 times and implementing this new process would reduce those failures to 1 out of 10 times".
Management needs to see improvements in terms of: reduced costs, icreased profits, reduced time, reduced use of resources. "Because it's widely used best practice" isn't going to be enough. Neither is, "because it makes my job easier".
Management often isn't aware of a problem because everyone is too afraid to say anything or assumes they can't possibly fail to see the problem. But your world is a different world than theirs.
I see at least two big problems:
1) Developers loading changes up themselves. All changes should come from source control. Do you encounter times where someone made a change that went to production but never got into source control and then was accidentally removed on the next deploy? How much time (money) was spent trying to figure out what went wrong there?
2) Lack of a clear promotion model. It seems like you guys are moving changes between environments rather than "builds". The key distinction is that if two changes work great in UAT because of how they interact, if only one change is promoted to production it could break there. Promoting consistent code - whether by labeling it or by just zipping up the whole web application and promoting the zip file - should cause fewer problems.
I work on the continuous integration and deployment solution, AnthillPro. How we address this with TFS is to retrieve the new code from TFS based on a date-time stamp (of when someone pressed the "Deliver to Stage" button).
This gives you most (all?) the traceability you would have of using tags, without actually having to go around tagging things. The system just records the time stamp, and every push of the code through the testing environments is tied to a known snapshot of code. We also have customers who lay down tags as part of the build process. As the first poster mentioned - CI is a good thing - less work, more traceability.
If you already have TFS, then you are almost there.
The place I'm at was using TFS for source control only. We have a similar setup with Dev/Stage/Prod. I took it upon myself to get a build server installed. Once that was done I added in the ability to auto deploy to dev for one of my projects and told a couple of the other guys about it. Initially the reception was luke warm.
Later I added TFS Deployer to the mix and have it set to auto deploy the good dev build to stage.
During this time the main group of developers were constantly fighting the "Did you get latest before deploying to Stage or Production?" questions; my stuff was working without a hitch. Believe me, management and the other devs noticed.
Now (6 months into it), we have a written rule that you aren't even allowed to use the Publish command in visual studio. EVERYTHING goes through the CI build and deployments. When moving to prod, our production group pulls the appropriate copy off of the build server. I even trained our QA group on how to do web testing and we're slowly integrating automated tests into the whole shebang.
The point of this ramble is that it took awhile. But more importantly it only happened because I was willing to just run with it and show results.
I suggest you do the same. Start using it, then show the benefits to get everyone else on board.
I've been pushing for continuous integration at my company since I joined 5 months ago, but having seen the type of applications we work on I'm starting to think that it might not be worth the effort of setting up each and every project for continuous integration.
If you work in a development department where the average project takes 2-3 weeks and once it's deployed you seldom if ever have to worry about it, is continuous integration worth the hassle of setting it up?
Probably depends on your process. If you have unit tests that cover your code, then continuous integration is worth every bit. I'm assuming that you guys all work on a single module of work as the projects are 2-3 weeks.
I don't think folks will run every test for every one of their commits and continuous integration helps a lot here.
The other reason would be if your project is highly modularized. I've worked in systems where there are lots of modules and a developer wouldn't be functional-testing the entire website before committing. Things might not even compile properly as the other module wouldn't even build because the developer did not checkout the complete code.
I'd recommend continuous integration anyway. With setups like Hudson and Cruisecontrol, it doesn't take a lot of time to set up and pays for itself quickly.
Personally, I think CI and the various processes it encourages are always useful. Getting CI setup is rather trivial once you have the server set up itself. You're basically just copying a configuration file from one project, editing it, and creating a new project. I wouldn't not use CI because of the "effort of setting up each and every project".
Continuous Integration is not only a tool matter, but also a set processes (commit regularly, have a version control system...).
Concerning the I.C software, you can install, configure and start to use Hudson in less than 10 minutes! So why would you go without any IC system?
It really depends on how fast you can set up an automated build and then get that hooked up to a CI server.
.NET
I've seen us go from no automated build to an automated build for a project in a few minutes using UppercuT. We use that and CruiseControl.NET (in the configuration, we add a line per project b/c we take advantage of the preprocessor).
http://code.google.com/p/uppercut/
Some good explanations here: UppercuT
If your many apps share any common components or modules, CI and tests will likely help you notice something breaking. If they are really all little throw away, self contained scripts then you might not need CI, but it's a tough call.
As others have pointed out, once CI is setup then adding a new project is trivial so I'd say go for it. One benefit you're going to see is that if any of your projects do ever change you've already got CI and hopefully your unit tests ready to go so you won't get any nasty surprises!
Continous Integration is not only ensuring stuff works, it also allows you to DOCUMENT and TEST the release process as it would be done by a new developer.
This ensures that the customer gets what has been tested, not what the developer just throws together from his harddisk.
This may be extremely important for maintainance purposes.
Reading this post has left me wondering; are nightly builds ever better for a situation than continuous integration? The consensus of the answers seems to be pretty lopsided in favor of continuous integration, is that evangelism or is there really no reason to use nightly builds when continuous integration is an option?
If you're really doing continuous integration with all available tests, nightly builds would be redundant, since the last thing checked in that day would already have been tested.
On the other hand, if your CI regime only involves running a subset of all available tests, for example because some of your tests take a long time to run, then you can use nightlies additionally to run all tests. This'll let you catch many bugs early, and if you can't catch them early, you can at least catch them overnight.
I don't know, though, if that's technically still CI, since you're only doing a "partial" build each time, by ignoring some of the tests.
In our organization, nightly builds and CI builds have two distinct purposes. The CI build is a 'latest code' build in which the unit tests are run against the last check in as you would expect. We also run several code metrics on the CI build.
For nightly builds, however, we only incorporate source code that has been through the peer review process and is deemed ready for testing.
This way, the nightly build always contains build that is 'feature ready' for testing, while the CI build contains features that while functional (to the extent that the unit tests pass) may not be ready to send the to the test group.
The test groups writes new CRs exclusively from one of the nightly builds as opposed to the CI build, although those are also available for informal exploratory type testing.
Yes, if you have a process you want attached to a build, but it is resource heavy. For example, on my team we run JTest during the nightly build. We can't run it during the day because:
It requires a lot of resources, which may not be available
It takes 4 hours to complete each time
If you have a nice robust CI process in place a "nightly" is still useful.
As mentioned, a "nightly" build can do exhaustive tests and perhaps some high-level system tests. End-to-end stuff.
The concept of a "nightly" build is easily understood by everyone in the organization. If you have trouble communicating CI builds out to other groups (for example, a QA group that doesn't have the same handle on Agile that the Dev group might) a "nightly" is a powerful and simple concept.
If your nightly is a separate set of resources, it can be managed separately and used to cut "gold" images with some claims to software integrity. For example, developer writes code, some trusted build system that dev can't touch builds it, QA tests the gold build and signs it. In such a situation, the nightly build functions like a production build system.
Just some thoughts.
In my professional opinion, the only reason to use nightly builds is when the build process takes so long that it can't complete in a "reasonable" amount of time.
For example, if your build process takes 5 hours to complete there is really no reason to do a build on check in.
Beyond that, there is so much value in knowing as soon as possible when a build fails that it overrides other concerns.
It depends on the purpose and length of each of your builds. Basically, you should identify what you are trying to learn from CI and decide if it is worth while spending the resources on running multiple builds.
We used continuous integration at my last job for a few different purposes.
First, we used it to make sure that the repository and thus the developers always had a version of the code that compiled. Few things are worse for team members than having to manage another person's broken changes through commenting, uncommenting, reverting and merging, because one person checked in bad code. For this, we had a build that ran instantaneously with no tests or other validation so we knew as soon as possible if the code was safe to update. Builds usually took about ten minutes and the machine was probably running around 50% on a normal workday. No documentation was generated here, just a quiet pass or a loud fail siren.
Second, we wanted to know as soon as possible whether or not any rules were broken. The quicker that you find a broken rule, the easier it is to fix. For this purpose, we had a separate machine that ran a full build and validation of the code. This machine was running 12-14 hours a day continuously on a normal workday. Email status of the build was sent out describing broken unit tests, code compliance, etc.
We stopped there as far as automatically triggered builds go. A nightly build on top of that seemed a bit extreme for us. But I suppose if you wanted to have a snapshot build archived daily, you may want to schedule a third build with the extra steps required for that. Though, we did have another build that wrapped up and archived our QA deployment artifacts for quick and easy deployment, but we only ever manually triggered that one.
I think the other posts cover the common reasons, like having a build process that takes "too long" or having to run only a subset of tests during the CI build. But there's another reason which is political.
In some organizations the official builds are handled by a minimally responsive build/infrastructure/release management/SCM team. In these cases you might put them in charge of the nightly build and then run the CI build out of development. This avoids a fight because their build remains "the official build" and your CI build give you the feedback you need.
We have both continuous integration and nightly builds in place. They serve two different purposes.
Our continuous integration mechanism builds the software and runs unit tests under the continuous integration suite.
Our nightly build tags the source under version control, builds the software, runs the unit tests under nightly build suite. The software built here is then used in various system tests and stress tests.
I think that one of the main differentiator for nightly build is system tests.
What constitutes a good CI build-process?
We use CI, but is deployment to production even a realistic CI goal when you have dependencies on several services that should be deployed too and other apps may depend on these too.
Is a good good CI build process good enough when its automated to QA and manual from there?
Well "it depends" :)
We use our CI system to:
build & unit test
deploy to single box, run intergration tests and code analisys
deploy to lab environment
run acceptance tests in prod-like system
drop builds that pass to code drop for prod deployment
This is for a greenfield project of about a dozen services and databases deployed to 20+ servers, that also had dependencies on half a dozen other 'external' services.
Using a CI tool to deploy your product to a production environment as a realistic goal? again... "it depends"
Why would you want to do this?
if you have the process you can roll changes (and roll back) faster and more often
less chance for human error
you can test the same deployment strategy in a test environment before going to production and catch issues earlier
Some technical things you have to address before you can answer this:
what is the uptime requirements for your system -- Are you allowed to have downtime or does it need to be up 24/7?
do you have change control processes in place that require human intervention/approval?
is your deployment robust enough for any component to roll back to a known-good state if a deployment fails?
is your system designed to handle different versions of services or clients in case one or several component deployments fails (and you have the above rollback to last known good)?
does the process have the smarts to handle a partial deployment where a component cannot handle mixed versions of its dependencies/clients?
how are you handing database deployment/upgrades?
do you have monitoring in place so you know when something goes wrong?
Here are a couple of recent related links about automation and building the tools you need.
When it comes down to it the more complex your system the more difficult it is do automate everything, but that does not mean it is not a worthy goal, it just takes a lot more effort and willpower to get it done -- everything from knowing the difficulties you're going to face, the problems you have to account for (failure will happen), the political challenges of building infrastructure (vs. more product features).
Now heres the big secret... the technical challenges are challenging but not impossible... the political challenges may be insurmountable. Everything about this costs money whether its dev time or buying 3rd party solutions. So really, can you build the $1K, $10K, $100K, or $1M solution?
Whatever solution you go for make sure the automation is robust first, complete second... i.e. make sure you have as robust a solution as you can for getting deployment to a test environment rather than a fragile solution that deploys to production.
CI is not intended as a deployment mechanism. It is good to have your CI execute any automated deployment to a QA/Test server, to ensure those aspects of your build work, but I would not use a CI system like Cruise Control or Bamboo as the means of deployment.
CI is for building the codebase periodically to automate execution of automated tests, verification of the codebase via static analysis and other checks of that nature.
Be sure you understand the idea behind a CI build. CI stands for Continuous Integration and CI builds are really intended to be throw-away builds that are performed when a developer checks code in to the source control system (or at some specified interval) to ensure that the newest changes do not break the code base (hence the idea of continuously integrating the changes to the code base).
To that end, the technology used for the actual build server process is largely irrelevant compared to what actually happens during the build. As #pdavis mentioned, the CI build should compile the code base, execute some code analysis (FxCop, StyleCop, Lint, etc.), execute unit tests and code coverage, and execute any other custom analysis you want performed that should impact the concept of a "successful" or "failed" build.
Having a CI build automatically deploy to an environment really doesn't fall under the control of a build server. That being said, you can always create a separate project that runs on the build server that handles the deployment when it detects certain conditions (such as a build completes successfuly), but that should always be done as a completely independent thing.
I am starting on a new project at work that I am really looking forward to. We are still in the initial design stage and have just recently completed the Logical System Architecture. We have ordered new servers for the testing and staging environments and are setting up a Continuous Integration (CI) build system based on Cruise Control (http://cruisecontrol.sourceforge.net/) and MSBuild (http://msdn2.microsoft.com/en-us/library/wea2sca5.aspx) which is basically an improved port of ANT. It appears that Visual Studio 2005 project and solution files are all now in MSBuild format. Cruise Control will be automatically pulling the source from Visual Source Safe (ok, it isn't Subversion but we can deal), compiling it, and then running it through fxCop (http://www.gotdotnet.com/Team/FxCop/), nUnit (http://www.nunit.org/), nCover (http://ncover.org/site/), and last but not lease Simian (http://www.redhillconsulting.com.au/products/simian/). Cruise Control has a pretty good website interface for displaying all of the compiled results from the various tools and can even display code changes from one build to the next. It also keeps track of all builds in a build history. I'm looking forward to the test driven development and think that this type of approach combined with nUnit/nCover should give us a pretty good idea before we roll out changes that we haven't broken anything. There are also plans to incorporate some type of automated user interface testing once we are far enough along in the project. Depending on the tool, this should be just a matter of installing the tool on the build server and calling it from Cruise Control. Sweet.
A good CI process will have full or nearly-full unit test coverage. Unit tests test classes and methods, vs. integration tests, which test multiple parts of the system. When you set up your CI builds, have them automate the unit tests. That way, the CI builds can run multiple times per day. We have ours set to run every 2 hours.
You can have longer running builds that run once per day. These can use other services and run integration tests.
I was watching a ThoughtWorks presentation (creators of Cruise Control) and they actually addressed this issue. Their answer is that NO deployment is too complex to test. Why? Because otherwise, your customers become your testers, which is exactly where you don't want to be.
If you have a complex deployment structure, set up a visualization server. Have it pretend to be all the systems you need to talk to. They can always start in a known good state, because you can reset to a clean image.
To answer your initial question, a good process is one which enables communication between the repository and the developers. If the repository is in a bad state (non-compiling code, failed tests, etc.), the developers know about it as soon as possible, so that they can correct it.
The later a bug is discovered, the costlier it is to fix. So bugs should be discovered as early as possible. This is the motivation behind CI.
A good CI should ensure catching as many bugs as possible. The whole application comprises of code (often in multiple languages), Database schema, deployment files etc. Errors in any of these can cause bugs - so the CI should try to exercise as many of them as possible.
CI does not replace a proper QA discipline. Also, CI need not be very comprehensive on day one of the project. One can start with a simple CI process that does basic compilation & unit testing initially. As you discover more classes of bugs in QA, you should adapt the CI process to try to catch future occurrences of those bugs. It can also involve static code-analysis checks, so that you can implement consistent coding and design ideals across the codebase.