A simple CLI tool to enforce the TDD practice. It follows principles erected by Kent Beck in "Test Driven Development: By Example" and allows to: can be used by beginners to help them learn TDD as well as by advanced users to provide them a smooth development workflow. is cross-platform, open source and granted under the GPL-3.0 License.

Feedback is in alpha stage. There are probably some small bugs, shortcomings and a lot to enhance. Any feedback is welcome. You can create a ticket on Github, direct message me on Twitter or email me.

How to install


It requires git to be accessible from the $PATH. Nothing else particular is required. embeds all it needs in its binary.


Download the latest binary that suits your computer. Unzip it and install the binary in a directory recognized by your $PATH variable. For instance, if you're a MacOs or a Linux user, you can move the tdd binary to /usr/local/bin/.

Yippee, you are now ready to use the tdd command!

How to use

The classical workflow

Start a new TDD session:

tdd new "a clear message that explains what I want to achieve"

The message of this TDD session will be used to commit your changes.

Then, start your classical TDD loop: write a failing test, write the minimum code needed to make it pass, run all your tests, refactor and ensure all your tests are still green. The only difference, is that to run your tests you'll now use:

tdd my_alias

Where my_alias is the command used to launch your tests. It's defined in the configuration file, but we'll get back to that later.

If after having launched tdd my_alias, your tests are green, then your code is automatically committed. Great! You can now refactor or write a new failing test. For both those actions, use tdd my_alias again.

If your tests are red and you have configured a timer for this alias, you'll receive soon a small notification encouraging you to take a smaller step.

The configuration file

At the root of your project, you must create a .tdd.yaml configuration file. It defines all the test aliases you want to use.

You can initialize a new configuration file with:

tdd config --init

Then, change it according to your needs.

You can validate an existing configuration file with:

tdd config --validate

Here is an example of a configuration file:

# .tdd.yaml
    ut: # I use "ut" for Unit Tests. Personally, I define a "ut" alias for all my projects
        command: docker-compose run --rm php vendor/bin/phpspec run -v
            amend: true # commits will be amended when tests are green
            add: "*.php doc/*" # all PHP files and all files present in the "doc" folder will be added to the index 
        timer: 60 # you'll receive a small notification if your steps are still red after 60 seconds
    ut_go: # another alias
        command: go test ./... -v
        # if no "git.amend" key is configured, commits won't be amended: the previous message will be reused
        # if no "git.add" key is configured, all files will be added to the index. It's equivalent to "git add ."
        # if no "timer" key is defined, no notification will pop

With this configuration file, you could launch your aliases ut and ut_go with respectively tdd ut and tdd ut_go. Please note that for the moment, the command key can not handle "complex" commands with &&, || or ;.

It's recommended to add the configuration files to your .gitignore_global:

echo ".tdd.yaml" >> ~/.gitignore_global

Using the todo list

While you're working on something you can think about fixing or improving something else. To not lose the focus, it's handy to note this idea in a todo list:

tdd todo "I should do this other thing"
tdd todo "oh, something else I think about too"

When you are ready, which means when your tests are green, you can pick a task from this list:

tdd do

The list of tasks is displayed:

Here is your todo list, which task do you want to tackle?
  > I should do this other thing
  > oh, something else I thought about too

Now you can select the item you want to work on, this will start a new TDD session by using this task as a commit message.

If you need to, you can clear this todo list at anytime with:

tdd done

It's recommended to add the todo list files to your .gitignore_global:

echo ".tdd.todo" >> ~/.gitignore_global


Why committing every time tests are green is important?

I can't remember the number of times I've been lost in my developments because I didn't know exactly what I should add or not for my current commit. CTRL-Z on this file, adding this file but not that one, checking local history to understand what happened, going back and forth... Huh, this chaos is exhausting!

Committing everytime tests are green totally frees the mind. When it's committed, that means the code works. It's simple as that. There is nothing else to remember.

Committing automatically the code, won't this screw my git history?

Surprisingly, I find it's quite the opposite. The tdd new command forces us to explain what we want to achieve, not the how. Which is exactly what should be good a git history.

Besides, we're doing TDD right? So why should we explain what we have done, after having done it? Let's apply the TDD cycle from the very beginning: first, we have to think about what to achieve.

To end that topic, keep also in mind that, if you want or need to, you can still rewrite the git history whenever you want.

Why launching a notification when tests have been red for too long will help me to practice TDD?

One of the most fundamental principle of TDD is to take baby steps. In the book "Test Driven Development: By Example", Kent Beck can't stop talking about how small the changes should be so that we can be smoothly driven by the tests.

Sadly, small is a vague metric which is impossible to measure. The only metric I found helpful is time. When I take too much time to turn my tests green that's a sign I've been taking a too big or a too difficult step. In that case, I cancel my current code, and restart with a smaller step.

If you're a complete TDD beginner, I suggest you to start with a 10 minutes timer. Try to reduce it week by week. After a few months of practice, you should be able to use easily a ~60 seconds timer for a development environment you master. Congratulations! You are now able to take small steps!

Why using a todo list will help me to practice TDD?

The purpose of this todo list is not to store tasks that will take us months to complete. It's not an alternative to the useless // TODO: fix this that we can find sometimes in our codebase.

Its goal is to minimize the red/green time: when the tests are failing, our only goal is to make them turn green quickly and easily. Anything that is not related to this precise goal should land in this todo list. Therefore, it should have a short lifetime; typically, one day maximum.

Created with 🤍 by @jjanvier_