I am aware of this question: https://stackoverflow.com/questions/428691/how-to-encourage-implementation-of-tdd
In my team, we write a lot of unit tests. But, in general the programmers tend to write unit tests after wrting the code. So, we first finish the module functionality and then write tests. Our coverage is around 70% for most modules. I have tried convincing my technical manager and my team members to do pure TDD wherein we first write tests and then the code, but invain. I think writing tests first allows us to discover design better. Am I just being finicky, especially when our coverage is quite high? If the answer to this question is no, then how do I talk to people to have a test-first approach.
EDIT: I think writing tests after writing code is an easier thing to do. People in my team have got accustomed to do this and are opposing any change.
I don’t know that there is a whole lot you can tell people to convince them of the value of TDD. You can cite what the experts have told us about it, and your own personal experiences, but if folks are not willing to give it a try, chances are low that you sharing this information with them will help.
My experience with TDD was basically that it sounded like a really good idea, but it never really worked out the way it was supposed to. Then one day I tried it again on a new task and ended up with a solution to the problem that was simpler than what I would have thought possible, due entirely to the fact that I had used TDD. I think when developers have this sort of experience it changes the way they look at things, and makes them more willing to try it in other situations.
The challenge is being able to demonstrate this to the other developers. One way you may be able to do this is with the use of a TDD Kata like this one from Roy Osherove (he uses it in his TDD Master Course). It is designed specifically to demonstrate the value in working in small steps, implementing only the code that is needed to make each test pass. This may show folks how the process works, and make them more comfortable with giving it a try.
There was also a coding exercise I heard about where you gave two groups/teams of developers a reasonably simple task, and asked one of the groups to use TDD, and make sure they followed the “simplest thing that could possibly work” rules, while the other team did things however they wanted. Then, once that is done, you have the teams switch tasks, but throw out the code written by each team, leaving only the tests. The teams are then supposed to recreate the code for the task. Typically you will find that the team who inherits the TDD code has a much easier time doing this.
Given all that, though, I think the best thing you can do personally is to start doing TDD yourself for as much of your work as possible. This has the potential to give you some very specific references for where and how TDD has proved to be beneficial within the context of the current project. In particular if you do code reviews your peers may notice the code that you are writing TDD is more concise, and easier to maintain than the code that has been writing without TDD. Your QA team may also notice a difference in the quality of the code, which is one of the things that you hear a lot about companies who move to TDD.