# git-check-assertions

🚧 Merely a proof-of-concept right now.

I recently wrote two blogs posts arguing that there might be some value in writing verifiable claims, i.e. assertions, inside of our commit messages:

* [Should we start writing verifiable claims in commit message?](https://sven.memcmp.org/2026-02-19-should-we-start-writing-verifiable-claims-in-commit-messages/)
* [Writing the steps to validate a test in the commit message](https://sven.memcmp.org/2026-02-20-writing-the-steps-to-validate-a-test-in-the-commit-message/)

This is a simple verifier for such assertions.

You include a small bash script inside your commit messages, and `git-check-assertions` will then check out every commit (from the point that your branch diverged from `main`), and verify that the script in the commit message runs successfully.

⚠️ Only run this on repositories and branches that you trust, since the `bash` scripts in the commit messages can do whatever they want.

## Building

```bash
nix build .?submodules=1
```

## Examples of commit messages

Assert that a commit builds:

~~~
```git-check-assertions
dotnet build
```
~~~

Assert that a commit builds and that the tests succeed:

~~~
```git-check-assertions
dotnet build
dotnet test --no-build
```
~~~

Assert that a commit builds, but that the tests do not succeed (`assert_fails` is a helper function included in `git-check-assertions`):

~~~
```git-check-assertions
dotnet build
assert_fails dotnet test --no-build
```
~~~

Assert that a commit builds, and that the tests fail with exactly the error that you expect:

~~~
```git-check-assertions
dotnet build
(assert_fails dotnet test --no-build) | grep "Invalid URL"
```
~~~

Assert that a commit builds, and that a specific change breaks the tests (as discussed [here](https://sven.memcmp.org/2026-02-20-writing-the-steps-to-validate-a-test-in-the-commit-message/)):

~~~
```git-check-assertions
dotnet test
sed -i '/crucial code/d' Main.fs
dotnet build
assert_fails dotnet test --no-build
```
~~~