Ask HN: Examples of famous OSS created using red-green-refactor TDD?

https://news.ycombinator.com/item?id=7322119

by cgopalan • 12 years ago

7 9 12 years ago

news.ycombinator.com

Am a big believer in test-driven-development where tests are written before or after code and serve as verification for programs. I am a skeptic when I hear tests can drive the design and you should strictly follow the red-green-refactor cycle to write production code. I want to be proven wrong. Are there famous successful projects (besides junit) that used this approach and that I can learn from?

kstenson• 12 years ago

Have a look at Uncle Bob's fitness app, IIRC this is written using the red green refactor cycle, in fact I would suspect most of his other code on github will be the same.

https://github.com/unclebob/fitnesse

cgopalan4• 12 years ago

Thanks but fitnesse is also a testing framework and none of the other repos seem to be well known, IMO. So it would be good to see other examples.

dalke3• 12 years ago

I believe there are things to learn from reviewing the FitNesse source code. I once looked at FitNesse as an example of TDD. I was, and am, doubtful of that technique as an improved method for good design.

I found a number of security holes. For example, the "files" resource was open to arbitrary directory traversal, so I could download any file on the system. (I reported it. It has since been fixed.)

One of the files I could download was the configuration file. It contains a hashed password, but the hash algorithm was trivial to break. Within a couple of hours I had a program which would generate a string that generates the same hash value. (This does not appear to have changed.) Schneier once wrote "There are two types of encryption: one that will prevent your sister from reading your diary and one that will prevent your government." The fitnesse.authentication.HashingCipher is of the first type, which is likely good enough for the purpose. However, something like <salt>+MD5 would be at least equally secure, shorter, and easier for others to understand.

Once I had a password to upload a file, there was another directory traversal error which would let me place a file anywhere on the file system. (This has since been fixed.)

There are still design errors. For example, to delete the file "foo.txt", do a GET request to http://localhost:8080/files?responder=deleteFile&filename=fo... . While FitNesse itself uses a POST, the handler can take a POST or a GET. This would easily allow someone to construct a malicious page which secretly wipes things from your server.

If you are Martin then don't follow this link: http://fitnesse.org/files?responder=deleteFile&filename=head... ;)

It's also still open to cross-site scripting. For example, http://localhost:8080/files?responder=%3Cscript%3Ealert%28%2... gives a "hi!" alert. Thus, if I can get a FitNesse admin to click on a well-crafted link then I can deface the site.

My conclusion was that TDD doesn't lead to any better security design than a non-TDD project. If your production code requires security then TDD isn't enough. My question to TDD people is: what other design techniques should one use in order to have a secure design?

So far I haven't gotten an answer.

I also noticed any number of places where the server, which claims to be an HTTP/1.1 server, doesn't actually follow the HTTP specification. For example, FitNesse does not include a "Date" header in the response, but section 14.18 of the spec says "Origin servers MUST include a Date header field in all responses, except in these cases", none of which include FitNesse. More esoteric, 5.1.2 of the spec says "all HTTP/1.1 servers MUST accept the absoluteURI form in requests, even though HTTP/1.1 clients will only generate them in requests to proxies", but FitNesse assumes the first character of the Request-URI is a "/", so accepts "GET $ HTTP/1.0" as a valid request line.

These are not critical details, and my own HTTP servers don't follow the details of the spec. For most people, the only important test is that the browsers can understand it.

My point here is only the observation that TDD doesn't give a better mechanism to ensure that the software design meets an external specification.

ricardobeat• 12 years ago

Ghost is developed using TDD. It might not be the strictest example, but a very successful one:

https://github.com/TryGhost/Ghost/

Choose any other random OSS, chances are it's using TDD/BDD in one form or another.

cgopalan4• 12 years ago

Thanks for the link. Would it be possible to elaborate as to how doing TDD made the algorithm evolve for you?

"TDD/BDD in one form or another". Theres the rub. That form mostly doesnt involve red-green-refactor and make the algorithm evolve from their tests. A lot of famous, widely-used open source software have tests, but doesnt mean they used red-green-refactor TDD. If you read my comment below the title, I am specifically looking for software that used the TDD method as prescribed by agile methodologists.

Ask HN: Examples of famous OSS created using red-green-refactor TDD?

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