Allow output of logging when running unit tests (#13556)

* Initial pass at enabling logging for unit tests

* Add to docs

* Bind debug for more test types

* Force everything

* Tidy up slightly

2 files changed, 10 insertions, 2 deletions

diff --git a/docs/faq_debug.md b/docs/faq_debug.md
index 13a649bfa..1afa38a62 100644
--- a/docs/faq_debug.md
+++ b/docs/faq_debug.md
@@ -28,7 +28,7 @@ For compatible platforms, [QMK Toolbox](https://github.com/qmk/qmk_toolbox) can
 
 Prefer a terminal based solution? [hid_listen](https://www.pjrc.com/teensy/hid_listen.html), provided by PJRC, can also be used to display debug messages. Prebuilt binaries for Windows,Linux,and MacOS are available.
 
-## Sending Your Own Debug Messages
+## Sending Your Own Debug Messages :id=debug-api
 
 Sometimes it's useful to print debug messages from within your [custom code](custom_quantum_functions.md). Doing so is pretty simple. Start by including `print.h` at the top of your file:
 
diff --git a/docs/unit_testing.md b/docs/unit_testing.md
index 82073a201..a0eef51cb 100644
--- a/docs/unit_testing.md
+++ b/docs/unit_testing.md
@@ -36,12 +36,20 @@ Note how there's several different tests, each mocking out a separate part. Also
 
 ## Running the Tests
 
-To run all the tests in the codebase, type `make test`. You can also run test matching a substring by typing `make test:matchingsubstring` Note that the tests are always compiled with the native compiler of your platform, so they are also run like any other program on your computer.
+To run all the tests in the codebase, type `make test:all`. You can also run test matching a substring by typing `make test:matchingsubstring` Note that the tests are always compiled with the native compiler of your platform, so they are also run like any other program on your computer.
 
 ## Debugging the Tests
 
 If there are problems with the tests, you can find the executable in the `./build/test` folder. You should be able to run those with GDB or a similar debugger.
 
+To forward any [debug messages](unit_testing.md#debug-api) to `stderr`, the tests can run with `DEBUG=1`. For example
+
+```console
+make test:all DEBUG=1
+```
+
+Alternatively, add `CONSOLE_ENABLE=yes` to the tests `rules.mk`.
+
 ## Full Integration Tests
 
 It's not yet possible to do a full integration test, where you would compile the whole firmware and define a keymap that you are going to test. However there are plans for doing that, because writing tests that way would probably be easier, at least for people that are not used to unit testing.