[Tests] Increase QMK test coverage (#13789)

* Add per-test keymaps

* Add better trace and info logs for failed unit-tests

* Add layer state assertion with tracing message

* Use individual test binaries configuration options

* Add basic qmk functionality tests

* Add tap hold configurations tests

* Add auto shift tests

* `qmk format-c

* Fix tests

Co-authored-by: Nick Brassel <nick@tzarc.org>

21 files changed, 1403 insertions, 0 deletions

diff --git a/tests/tap_hold_configurations/default_mod_tap/config.h b/tests/tap_hold_configurations/default_mod_tap/config.h
new file mode 100644
index 000000000..5955b8600
--- /dev/null
+++ b/tests/tap_hold_configurations/default_mod_tap/config.h
@@ -0,0 +1,21 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define IGNORE_MOD_TAP_INTERRUPT
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/default_mod_tap/test.mk b/tests/tap_hold_configurations/default_mod_tap/test.mk
new file mode 100644
index 000000000..cfab996e0
--- /dev/null
+++ b/tests/tap_hold_configurations/default_mod_tap/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/default_mod_tap/test_tap_hold.cpp b/tests/tap_hold_configurations/default_mod_tap/test_tap_hold.cpp
new file mode 100644
index 000000000..90befcdff
--- /dev/null
+++ b/tests/tap_hold_configurations/default_mod_tap/test_tap_hold.cpp
@@ -0,0 +1,230 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class DefaultTapHold : public TestFixture {};
+
+TEST_F(DefaultTapHold, tap_regular_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       regular_key      = KeymapKey(0, 2, 0, KC_A);
+
+    set_keymap({mod_tap_hold_key, regular_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Idle for tapping term of mod tap hold key. */
+    idle_for(TAPPING_TERM - 3);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(DefaultTapHold, tap_mod_tap_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       first_mod_tap_hold_key  = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       second_mod_tap_hold_key = KeymapKey(0, 2, 0, RSFT_T(KC_A));
+
+    set_keymap({first_mod_tap_hold_key, second_mod_tap_hold_key});
+
+    /* Press first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    first_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    first_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(DefaultTapHold, tap_regular_key_while_layer_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       layer_tap_hold_key = KeymapKey(0, 1, 0, LT(1, KC_P));
+    auto       regular_key        = KeymapKey(0, 2, 0, KC_A);
+    auto       layer_key          = KeymapKey(1, 2, 0, KC_B);
+
+    set_keymap({layer_tap_hold_key, regular_key, layer_key});
+
+    /* Press layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    layer_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_A, KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(_));
+    layer_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(DefaultTapHold, tap_mod_tap_hold_key_two_times) {
+    GTEST_SKIP() << "TODO:Holding a modtap key results in out of bounds access to the keymap, this is a bug in QMK.";
+
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod-tap-hold key again. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(DefaultTapHold, tap_mod_tap_hold_key_twice_and_hold_on_second_time) {
+    GTEST_SKIP() << "TODO:Holding a modtap key results in out of bounds access to the keymap, this is a bug in QMK.";
+
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod-tap-hold key again. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(DefaultTapHold, tap_and_hold_mod_tap_hold_key) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM + 1);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/ignore_mod_tap_interrupt/config.h b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/config.h
new file mode 100644
index 000000000..5955b8600
--- /dev/null
+++ b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/config.h
@@ -0,0 +1,21 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define IGNORE_MOD_TAP_INTERRUPT
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test.mk b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test.mk
new file mode 100644
index 000000000..efecca2c2
--- /dev/null
+++ b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
diff --git a/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test_tap_hold.cpp b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test_tap_hold.cpp
new file mode 100644
index 000000000..1702d604d
--- /dev/null
+++ b/tests/tap_hold_configurations/ignore_mod_tap_interrupt/test_tap_hold.cpp
@@ -0,0 +1,136 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class IgnoreModTapInterrupt : public TestFixture {};
+
+TEST_F(IgnoreModTapInterrupt, tap_regular_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       regular_key      = KeymapKey(0, 2, 0, KC_A);
+
+    set_keymap({mod_tap_hold_key, regular_key});
+
+    /* Press mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_A, KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(IgnoreModTapInterrupt, tap_mod_tap_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       first_mod_tap_hold_key  = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       second_mod_tap_hold_key = KeymapKey(0, 2, 0, RSFT_T(KC_A));
+
+    set_keymap({first_mod_tap_hold_key, second_mod_tap_hold_key});
+
+    /* Press first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    first_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_A, KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    first_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(IgnoreModTapInterrupt, tap_regular_key_while_layer_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       layer_tap_hold_key = KeymapKey(0, 1, 0, LT(1, KC_P));
+    auto       regular_key        = KeymapKey(0, 2, 0, KC_A);
+    auto       layer_key          = KeymapKey(1, 2, 0, KC_B);
+
+    set_keymap({layer_tap_hold_key, regular_key, layer_key});
+
+    /* Press layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    layer_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P, regular_key.report_code)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    layer_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
diff --git a/tests/tap_hold_configurations/permissive_hold/config.h b/tests/tap_hold_configurations/permissive_hold/config.h
new file mode 100644
index 000000000..2d5a9849e
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold/config.h
@@ -0,0 +1,21 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define PERMISSIVE_HOLD
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/permissive_hold/test.mk b/tests/tap_hold_configurations/permissive_hold/test.mk
new file mode 100644
index 000000000..efecca2c2
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
diff --git a/tests/tap_hold_configurations/permissive_hold/test_one_shot_keys.cpp b/tests/tap_hold_configurations/permissive_hold/test_one_shot_keys.cpp
new file mode 100644
index 000000000..aa71ec397
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold/test_one_shot_keys.cpp
@@ -0,0 +1,76 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "action_util.h"
+#include "keyboard_report_util.hpp"
+#include "test_common.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class OneShot : public TestFixture {};
+class OneShotParametrizedTestFixture : public ::testing::WithParamInterface<std::pair<KeymapKey, KeymapKey>>, public OneShot {};
+
+TEST_P(OneShotParametrizedTestFixture, OSMAsRegularModifierWithAdditionalKeypress) {
+    TestDriver driver;
+    KeymapKey  osm_key     = GetParam().first;
+    KeymapKey  regular_key = GetParam().second;
+
+    set_keymap({osm_key, regular_key});
+
+    /* Press OSM */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    osm_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(osm_key.report_code))).Times(2);
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(regular_key.report_code, osm_key.report_code))).Times(1);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release OSM */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport())).Times(1);
+    osm_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+// clang-format off
+
+INSTANTIATE_TEST_CASE_P(
+    OneShotModifierTests,
+    OneShotParametrizedTestFixture,
+    ::testing::Values(
+        /* first is osm key, second is regular key. */
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_LSFT), KC_LSFT}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_LCTL), KC_LCTL}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_LALT), KC_LALT}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_LGUI), KC_LGUI}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_RCTL), KC_RCTL}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_RSFT), KC_RSFT}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_RALT), KC_RALT}, KeymapKey{0, 1, 1, KC_A}),
+        std::make_pair(KeymapKey{0, 0, 0, OSM(MOD_RGUI), KC_RGUI}, KeymapKey{0, 1, 1, KC_A})
+        ));
+// clang-format on
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/permissive_hold/test_tap_hold.cpp b/tests/tap_hold_configurations/permissive_hold/test_tap_hold.cpp
new file mode 100644
index 000000000..ab9dd1518
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold/test_tap_hold.cpp
@@ -0,0 +1,132 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+class PermissiveHold : public TestFixture {};
+
+TEST_F(PermissiveHold, tap_regular_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       regular_key      = KeymapKey(0, 2, 0, KC_A);
+
+    set_keymap({mod_tap_hold_key, regular_key});
+
+    /* Press mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT, regular_key.report_code)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(PermissiveHold, tap_mod_tap_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       first_mod_tap_hold_key  = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       second_mod_tap_hold_key = KeymapKey(0, 2, 0, RSFT_T(KC_A));
+
+    set_keymap({first_mod_tap_hold_key, second_mod_tap_hold_key});
+
+    /* Press first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    first_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press second mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release second mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT, second_mod_tap_hold_key.report_code)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    second_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    first_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(PermissiveHold, tap_regular_key_while_layer_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       layer_tap_hold_key = KeymapKey(0, 1, 0, LT(1, KC_P));
+    auto       regular_key        = KeymapKey(0, 2, 0, KC_A);
+    auto       layer_key          = KeymapKey(1, 2, 0, KC_B);
+
+    set_keymap({layer_tap_hold_key, regular_key, layer_key});
+
+    /* Press layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    layer_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(layer_key.report_code)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    layer_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/config.h b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/config.h
new file mode 100644
index 000000000..a6abd50bb
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/config.h
@@ -0,0 +1,22 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define IGNORE_MOD_TAP_INTERRUPT
+#define PERMISSIVE_HOLD
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test.mk b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test.mk
new file mode 100644
index 000000000..efecca2c2
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
diff --git a/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test_tap_hold.cpp b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test_tap_hold.cpp
new file mode 100644
index 000000000..67f394653
--- /dev/null
+++ b/tests/tap_hold_configurations/permissive_hold_ignore_mod_tap_interrupt/test_tap_hold.cpp
@@ -0,0 +1,134 @@
+
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class PermissiveHold_IgnoreModTapInterrupt : public TestFixture {};
+
+TEST_F(PermissiveHold_IgnoreModTapInterrupt, tap_regular_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       regular_key      = KeymapKey(0, 2, 0, KC_A);
+
+    set_keymap({mod_tap_hold_key, regular_key});
+
+    /* Press mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(PermissiveHold_IgnoreModTapInterrupt, tap_mod_tap_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       first_mod_tap_hold_key  = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       second_mod_tap_hold_key = KeymapKey(0, 2, 0, RSFT_T(KC_A));
+
+    set_keymap({first_mod_tap_hold_key, second_mod_tap_hold_key});
+
+    /* Press first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    first_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    second_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    first_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(PermissiveHold_IgnoreModTapInterrupt, tap_regular_key_while_layer_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       layer_tap_hold_key = KeymapKey(0, 1, 0, LT(1, KC_P));
+    auto       regular_key        = KeymapKey(0, 2, 0, KC_A);
+    auto       layer_key          = KeymapKey(1, 2, 0, KC_B);
+
+    set_keymap({layer_tap_hold_key, regular_key, layer_key});
+
+    /* Press layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    layer_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_B)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    layer_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/retro_tapping/config.h b/tests/tap_hold_configurations/retro_tapping/config.h
new file mode 100644
index 000000000..4b38f2644
--- /dev/null
+++ b/tests/tap_hold_configurations/retro_tapping/config.h
@@ -0,0 +1,21 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define RETRO_TAPPING
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/retro_tapping/test.mk b/tests/tap_hold_configurations/retro_tapping/test.mk
new file mode 100644
index 000000000..efecca2c2
--- /dev/null
+++ b/tests/tap_hold_configurations/retro_tapping/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
diff --git a/tests/tap_hold_configurations/retro_tapping/test_tap_hold.cpp b/tests/tap_hold_configurations/retro_tapping/test_tap_hold.cpp
new file mode 100644
index 000000000..59ae77f78
--- /dev/null
+++ b/tests/tap_hold_configurations/retro_tapping/test_tap_hold.cpp
@@ -0,0 +1,52 @@
+
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class RetroTapping : public TestFixture {};
+
+TEST_F(RetroTapping, tap_and_hold_mod_tap_hold_key) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    /* TODO: Why is LSHIFT send at all? */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/retro_tapping/test_tapping.cpp b/tests/tap_hold_configurations/retro_tapping/test_tapping.cpp
new file mode 100644
index 000000000..cf23df831
--- /dev/null
+++ b/tests/tap_hold_configurations/retro_tapping/test_tapping.cpp
@@ -0,0 +1,112 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class Tapping : public TestFixture {};
+
+TEST_F(Tapping, HoldA_SHFT_T_KeyReportsShift) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 7, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(Tapping, ANewTapWithinTappingTermIsBuggy) {
+    TestDriver driver;
+    InSequence s;
+    auto       key_shift_hold_p_tap = KeymapKey(0, 7, 0, SFT_T(KC_P));
+
+    set_keymap({key_shift_hold_p_tap});
+
+    /* Press mod_tap_hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    key_shift_hold_p_tap.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod_tap_hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    key_shift_hold_p_tap.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod_tap_hold key again */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    key_shift_hold_p_tap.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod_tap_hold key again */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    key_shift_hold_p_tap.release();
+    idle_for(TAPPING_TERM + 1);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod_tap_hold key again */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    key_shift_hold_p_tap.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod_tap_hold key again */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    key_shift_hold_p_tap.release();
+    idle_for(TAPPING_TERM + 1);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod_tap_hold key again */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    key_shift_hold_p_tap.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod_tap_hold key again */
+    /* TODO: Why is KC_LSFT send? */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    key_shift_hold_p_tap.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/tapping_force_hold/config.h b/tests/tap_hold_configurations/tapping_force_hold/config.h
new file mode 100644
index 000000000..3b4646338
--- /dev/null
+++ b/tests/tap_hold_configurations/tapping_force_hold/config.h
@@ -0,0 +1,21 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "test_common.h"
+
+#define TAPPING_FORCE_HOLD
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/tapping_force_hold/test.mk b/tests/tap_hold_configurations/tapping_force_hold/test.mk
new file mode 100644
index 000000000..efecca2c2
--- /dev/null
+++ b/tests/tap_hold_configurations/tapping_force_hold/test.mk
@@ -0,0 +1,18 @@
+# Copyright 2021 Stefan Kerkmann
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# --------------------------------------------------------------------------------
+# Keep this file, even if it is empty, as a marker that this folder contains tests
+# --------------------------------------------------------------------------------
diff --git a/tests/tap_hold_configurations/tapping_force_hold/test_action_layer.cpp b/tests/tap_hold_configurations/tapping_force_hold/test_action_layer.cpp
new file mode 100644
index 000000000..02416eed7
--- /dev/null
+++ b/tests/tap_hold_configurations/tapping_force_hold/test_action_layer.cpp
@@ -0,0 +1,81 @@
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "test_common.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class ActionLayer : public TestFixture {};
+
+TEST_F(ActionLayer, LayerTapToggleWithToggleWithKeypress) {
+    TestDriver driver;
+    KeymapKey  layer_key = KeymapKey{0, 0, 0, TT(1)};
+
+    /* These keys must have the same position in the matrix, only the layer is different. */
+    KeymapKey regular_key = KeymapKey{0, 1, 0, KC_A};
+    set_keymap({layer_key, regular_key, KeymapKey{1, 1, 0, KC_B}});
+
+    /* Tap TT five times . */
+    /* TODO: QMK currently sends an empty report even if nothing needs to be reported to the host! */
+    /* TODO: Tapping Force Hold breaks TT */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport())).Times(10);
+
+    layer_key.press();
+    run_one_scan_loop();
+    layer_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+
+    layer_key.press();
+    run_one_scan_loop();
+    layer_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+
+    layer_key.press();
+    run_one_scan_loop();
+    layer_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+
+    layer_key.press();
+    run_one_scan_loop();
+    layer_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+
+    layer_key.press();
+    run_one_scan_loop();
+    layer_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_A))).Times(1);
+    regular_key.press();
+    run_one_scan_loop();
+    expect_layer_state(0);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport())).Times(1);
+    regular_key.release();
+    run_one_scan_loop();
+    expect_layer_state(0);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
\ No newline at end of file
diff --git a/tests/tap_hold_configurations/tapping_force_hold/test_tap_hold.cpp b/tests/tap_hold_configurations/tapping_force_hold/test_tap_hold.cpp
new file mode 100644
index 000000000..cb6842961
--- /dev/null
+++ b/tests/tap_hold_configurations/tapping_force_hold/test_tap_hold.cpp
@@ -0,0 +1,215 @@
+
+/* Copyright 2021 Stefan Kerkmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keyboard_report_util.hpp"
+#include "keycode.h"
+#include "test_common.hpp"
+#include "action_tapping.h"
+#include "test_fixture.hpp"
+#include "test_keymap_key.hpp"
+
+using testing::_;
+using testing::InSequence;
+
+class TappingForceHold : public TestFixture {};
+
+TEST_F(TappingForceHold, tap_regular_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       regular_key      = KeymapKey(0, 2, 0, KC_A);
+
+    set_keymap({mod_tap_hold_key, regular_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Idle for tapping term of mod tap hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    idle_for(TAPPING_TERM - 3);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(TappingForceHold, tap_mod_tap_key_while_mod_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       first_mod_tap_hold_key  = KeymapKey(0, 1, 0, SFT_T(KC_P));
+    auto       second_mod_tap_hold_key = KeymapKey(0, 2, 0, RSFT_T(KC_A));
+
+    set_keymap({first_mod_tap_hold_key, second_mod_tap_hold_key});
+
+    /* Press first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    first_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release second tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    second_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release first mod-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    first_mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Idle for tapping term of first mod tap hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT, KC_A)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    idle_for(TAPPING_TERM - 3);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(TappingForceHold, tap_regular_key_while_layer_tap_key_is_held) {
+    TestDriver driver;
+    InSequence s;
+    auto       layer_tap_hold_key = KeymapKey(0, 1, 0, LT(1, KC_P));
+    auto       regular_key        = KeymapKey(0, 2, 0, KC_A);
+    auto       layer_key          = KeymapKey(1, 2, 0, KC_B);
+
+    set_keymap({layer_tap_hold_key, regular_key, layer_key});
+
+    /* Press layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    layer_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release regular key */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    regular_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release layer-tap-hold key */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_A, KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(_));
+    layer_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(TappingForceHold, tap_mod_tap_hold_key_two_times) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod-tap-hold key again. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}
+
+TEST_F(TappingForceHold, tap_mod_tap_hold_key_twice_and_hold_on_second_time) {
+    TestDriver driver;
+    InSequence s;
+    auto       mod_tap_hold_key = KeymapKey(0, 1, 0, SFT_T(KC_P));
+
+    set_keymap({mod_tap_hold_key});
+
+    /* Press mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_P)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Press mod-tap-hold key again. */
+    EXPECT_CALL(driver, send_keyboard_mock(_)).Times(0);
+    mod_tap_hold_key.press();
+    idle_for(TAPPING_TERM);
+    testing::Mock::VerifyAndClearExpectations(&driver);
+
+    /* Release mod-tap-hold key. */
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport(KC_LSHIFT)));
+    EXPECT_CALL(driver, send_keyboard_mock(KeyboardReport()));
+    mod_tap_hold_key.release();
+    run_one_scan_loop();
+    testing::Mock::VerifyAndClearExpectations(&driver);
+}