5 files changed, 59 insertions, 6 deletions

diff --git a/build_test.mk b/build_test.mk
index 77c4265f9..519c142c4 100644
--- a/build_test.mk
+++ b/build_test.mk
@@ -24,7 +24,6 @@ GTEST_INTERNAL_INC :=\
 
 $(GTEST_OUTPUT)_SRC :=\
         googletest/src/gtest-all.cc\
-        googletest/src/gtest_main.cc\
         googlemock/src/gmock-all.cc
 
 $(GTEST_OUTPUT)_DEFS :=
@@ -35,7 +34,8 @@ CREATE_MAP := no
 
 VPATH +=\
         $(LIB_PATH)/googletest\
-        $(LIB_PATH)/googlemock
+        $(LIB_PATH)/googlemock\
+        $(LIB_PATH)/printf
 
 all: elf
 
@@ -43,6 +43,10 @@ VPATH += $(COMMON_VPATH)
 PLATFORM:=TEST
 PLATFORM_KEY:=test
 
+ifeq ($(strip $(DEBUG)), 1)
+CONSOLE_ENABLE = yes
+endif
+
 ifneq ($(filter $(FULL_TESTS),$(TEST)),)
 include tests/$(TEST)/rules.mk
 endif
@@ -55,6 +59,11 @@ ifneq ($(filter $(FULL_TESTS),$(TEST)),)
 include build_full_test.mk
 endif
 
+$(TEST)_SRC += \
+        tests/test_common/main.c \
+        $(LIB_PATH)/printf/printf.c \
+        $(COMMON_DIR)/printf.c
+
 $(TEST_OBJ)/$(TEST)_SRC := $($(TEST)_SRC)
 $(TEST_OBJ)/$(TEST)_INC := $($(TEST)_INC) $(VPATH) $(GTEST_INC)
 $(TEST_OBJ)/$(TEST)_DEFS := $($(TEST)_DEFS)
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.
diff --git a/tests/test_common/main.cpp b/tests/test_common/main.cpp
new file mode 100644
index 000000000..3e4b4c0f9
--- /dev/null
+++ b/tests/test_common/main.cpp
@@ -0,0 +1,32 @@
+#include "gtest/gtest.h"
+
+extern "C" {
+#include "stdio.h"
+#include "debug.h"
+
+int8_t sendchar(uint8_t c) {
+    fprintf(stderr, "%c", c);
+    return 0;
+}
+
+__attribute__((weak)) debug_config_t debug_config = {0};
+
+void init_logging(void) {
+    print_set_sendchar(sendchar);
+
+    // Customise these values to desired behaviour
+    // debug_enable   = true;
+    // debug_matrix   = true;
+    // debug_keyboard = true;
+    // debug_mouse    = true;
+    debug_config.raw = 0xFF;
+}
+}
+
+int main(int argc, char **argv) {
+    ::testing::InitGoogleTest(&argc, argv);
+
+    init_logging();
+
+    return RUN_ALL_TESTS();
+}
\ No newline at end of file
diff --git a/tests/test_common/test_fixture.cpp b/tests/test_common/test_fixture.cpp
index 20ed838eb..e041df712 100644
--- a/tests/test_common/test_fixture.cpp
+++ b/tests/test_common/test_fixture.cpp
@@ -7,10 +7,10 @@
 #include "action_tapping.h"
 
 extern "C" {
+#include "debug.h"
+#include "eeconfig.h"
 #include "action_layer.h"
-}
 
-extern "C" {
 void set_time(uint32_t t);
 void advance_time(uint32_t ms);
 }
@@ -21,6 +21,10 @@ using testing::Between;
 using testing::Return;
 
 void TestFixture::SetUpTestCase() {
+    // The following is enough to bootstrap the values set in main
+    eeconfig_init_quantum();
+    eeconfig_update_debug(debug_config.raw);
+
     TestDriver driver;
     EXPECT_CALL(driver, send_keyboard_mock(_));
     keyboard_init();