Executing visual studio 2010 unit tests without installing visual studio

In a previous post I already explained how to get your unit tests running on a build machine with mstest.exe, without having to install Visual Studio 2008. We recently upgraded to Visual Studio 2010 so I had to repeat the exercise.

This time I wrote a batch script which does most of the work. Just run the script on a machine where Visual Studio 2010 is installed, and it will create a "mstest" folder with the necessary binaries and registry entries. Copy the folder to your build machine, prepare the registry by executing mstest.reg and you're good to run mstest.exe like this:

mstest /noisolation /testcontainer:"path\to\testproject.dll"

This will return an error code if any of the tests fail.

As an anonymous commenter on my previous post pointed out, you should be careful of the license implications. In our case it is most likely OK because we have a site license. But even so it can be useful to avoid a full Visual Studio install: it saves a lot of disk space, and you don't have to spend time babysitting the installation. Or multiple installations, if you have a cluster of build machines!

update: thanks to Frederic Torres for pointing out that the script doesn't work on a 64-bit Windows, and suggesting a fix! It should work now. Apparently there are still problems with 64-bit machines. But I don't have a 64-bit machine without VS2010 to test with, so I'll have to leave it as an exercise for the reader...

bisect your source code history to find the problematic revision

I am working on a little application to edit Markdown documents with instant preview. (For those of you who aren't into building things from source, here's a windows installer to put a downmarker shortcut in your start menu.) I like to use both windows and linux so I try to make sure that it runs on both Microsoft.NET and Mono.

When I last tested my application on Mono, I discovered a very annoying problem: each time I tried to type something in a markdown document, a new nautilus file browser window would be launched! I had absolutely no idea why this would happen or where to start debugging. To make matters worse, I hadn't tested on Mono for about 40 revisions so there were a lot of possible changes that might have introduced the problem.

I have the source code history in a mercurial repository, so I decided to give the "bisect" feature a try. I started by marking the latest revision as "known bad":

hg bisect --bad

I also remembered making some mono-specific bug fixes, and the problem didn't exist at that point. So I grepped the output of hg log for commit messages containing the word "mono" and marked the revision as good:

hg bisect --good 627d6

At this point the bisect command has a revision range to work with. It will automatically update your working copy to a revision right in the middle of that range. You just have to rebuild your application, verify whether the problem is still there, and mark the revision as good or bad. (It is also possible to do this test automatically with a script.) The bisect command will then automatically cut the revision range to investigate in half again, and select yet another revision in the middle, etcetera.

Sure enough, after about 5 or 6 tests I got this message:

The first bad revision is:
changeset:   42:c4bbabe79dde
user:        wcoenen
date:        Sun Nov 07 23:31:32 2010 +0100
summary:     Links are now handled by opening .md or by external application.

Aha! Looks like I added some code to handle link clicks by passing the URL to the OS (to open it with a suitable external application). And obviously this code is now being triggered erroneously on mono whenever the document is updated. Thank you bisect!

git error: error setting certificate verify locations

I was trying to clone a repository from github when I ran into this error:

Cloning into docu...
error: error setting certificate verify locations:
  CAfile: \bin\curl-ca-bundle.crt
  CApath: none
 while accessing https://github.com/jagregory/docu/info/refs

If you google around, many people "solve" this by disabling the SSL certificate check entirely. Obviously there is a reason for that check, so disabling it is not quite the right solution! It turns out that there is mistake in the gitconfig file that comes with msgit setup (I have Git-1.7.2.3 installed). The right fix is to change the sslCAinfo setting in "c:\program files\git\etc\gitconf" to this:

sslCAinfo = c:\\program files\\git\\bin\\curl-ca-bundle.crt

Mercurial and subversion subrepos

It is not yet mentioned in the Mercurial book, but Mercurial has a subrepos feature to pull code from other repositories into your project as a nested repository. It is a bit similar to SVN externals and git submodules.

Better yet, it also works with subversion! There are still some bugs to be worked out though: you better not move your SVN subrepo around in your mercurial repository. For all the ugly details, see my bug report.

An equivalent of .bashrc for the windows cmd.exe shell

Tired of the "cd" command in windows refusing to navigate to folders on other drives? Put this in the [HKEY_CURRENT_USER\Software\Microsoft\Command Processor] AutoRun key:

c:\cmdauto.cmd

This will cause the given script to be executed each time a cmd.exe window is opened. I found out about that thanks to this superuser.com post.

Now put this in c:\cmdauto.cmd

@echo off
doskey cd=pushd $*

The doskey command creates aliases, here overriding the behavior of "cd".

ZFS-Fuse reliability report

A few weeks ago, I got this question in the comments on my last NAS post:

Since you've been using ZFS-fuse for a time now, can you report here or blog about its stability? Has the daemon crashed on you, while taking a snapshot, or while "scrub"-ing?

How much data have you passed in?

First, note that the version of ZFS-FUSE which I am using is not a particular release, but this revision from the official git repository. I have not bothered to update my ZFS binaries since January, because I didn't encounter any problems.

The "zfs list" output for my pool shows that I am using 352 GiB. The pool consists of two 465 GiB disks in a mirror setup.

NAME               USED  AVAIL  REFER  MOUNTPOINT
nas-pool           352G   105G    24K  /nas-pool
nas-pool/archive   118G   105G  71.1G  /nas-pool/archive
nas-pool/bulk      234G   105G   228G  /nas-pool/bulk

The pool is scrubbed by a cron script each sunday night. I have not seen any crashes/hangs during scrubbing. The scrubs have not detected any errors so far.

"archive" is snapshotted every night. "bulk" is snapshotted" only on sunday nights. The pool contains more than a hundred snapshots. Again, I have not seen any crashes or hangs.

Then there is read/write activity: I use it to automatically archive my emails from Gmail (nightly), sync with my dropbox folder (continuously), and to store my mp3s, photos, videos, downloads and backups when I need to. When reading or writing NAS files, I am usually working from my laptop over WiFi which is a speed bottleneck, so this probably doesn't really stress the file system. On the other hand, I do regularly make a full off-line backup of the "archive" filesystem by hooking up an external USB disk to the NAS. I haven't seen ZFS crash during any of this.

From this, I conclude that ZFS-Fuse is pretty stable.

Exponential growth has limits

I saw this comment in the thread of a slashdot post about Wall Street today:

But everything thus far shows us that perpetual growth is possible. Technology is a wonderful thing - each year we're able to do more with less.

That's not to say that a lot of what goes on in the market isn't pure, unadulterated bullshit, but real, honest-to-goodness "growth" won't stop until technology does.

This is a textbook example of the "cornucopian" view on economics. The implicit assumption here is that there are no limits to technological improvements, or that those limits are extremely far in our future. I think that this assumption is flat out wrong and dangerous. It is these sorts of ideas which have lead large parts of the global economy to eerily resemble Ponzi Schemes.

I wrote the following post in reply:

There are limits to exponential growth. (And make no mistake, growth expressed as a fixed percentage per year is exponential). Technology can push the limits closer to what the laws of physics allow, but technology cannot change the laws of physics.

Let's look at some numbers to drive the point home. Our global energy consumption in 2008 was estimated to be 474 exajoules.

The total energy received by the earth from the sun during a year is about 5 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!

Think about that: if energy consumption growth continues at the current pace, then in 500 years we'll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we'll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.

Granted, you did say "do more with less". So lets say energy consumption will stay constant in the future, and instead we'll derive 2% more "value" from the same energy each year. Now you run into a new problem. No matter how you define "value", you run into physical limits. If you define value as "amount of mass lifted out of the earth's gravity field", then the hard efficiency limit is a minimum of 60 megajoules per kg. If you define value as "amount of computation", then again there are limits given by the laws of physics.

Exponential growth is counterintuitive. No matter how far you push the limits (e.g. by colonizing the entire galaxy or inventing game-changing technology), exponential growth will hit its limits much faster than you think. We're talking about growth with a fixed doubling period here.

Finally, I'd argue that we are already experiencing the end of exponential growth today. After decades of growth, in 2004 global oil production reached a plateau [theoildrum.com]. It's not a coincidence that we experienced a major financial crash and recession soon after that. The era of "perpetual growth" is over. The next era will be that of the "zero-sum game" at best.

On a related note, after writing the above post I stumbled on this excellent series of videos of a lecture by Dr. Albert A. Bartlett where he shows with some very simple calculations and examples that "steady growth" is in fact always unsustainable. We have to find a way to get our civilization to work with 0% growth. The alternative is total collapse, probably within decades.