diff --git a/build_test.mk b/build_test.mk
index a5d63adab49..136a0455f01 100644
--- a/build_test.mk
+++ b/build_test.mk
@@ -58,6 +58,7 @@ include $(BUILDDEFS_PATH)/generic_features.mk
 include $(PLATFORM_PATH)/common.mk
 include $(TMK_PATH)/protocol.mk
 include $(QUANTUM_PATH)/debounce/tests/rules.mk
+include $(QUANTUM_PATH)/encoder/tests/rules.mk
 include $(QUANTUM_PATH)/sequencer/tests/rules.mk
 include $(PLATFORM_PATH)/test/rules.mk
 ifneq ($(filter $(FULL_TESTS),$(TEST)),)
diff --git a/quantum/encoder/tests/encoder_tests.cpp b/quantum/encoder/tests/encoder_tests.cpp
new file mode 100644
index 00000000000..1888fdab8d0
--- /dev/null
+++ b/quantum/encoder/tests/encoder_tests.cpp
@@ -0,0 +1,144 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 "gtest/gtest.h"
+#include "gmock/gmock.h"
+#include <vector>
+#include <algorithm>
+#include <stdio.h>
+
+extern "C" {
+#include "encoder.h"
+#include "encoder/tests/mock.h"
+}
+
+struct update {
+    int8_t index;
+    bool   clockwise;
+};
+
+uint8_t uidx = 0;
+update  updates[32];
+
+bool encoder_update_kb(uint8_t index, bool clockwise) {
+    updates[uidx % 32] = {index, clockwise};
+    uidx++;
+    return true;
+}
+
+bool setAndRead(pin_t pin, bool val) {
+    setPin(pin, val);
+    return encoder_read();
+}
+
+class EncoderTest : public ::testing::Test {};
+
+TEST_F(EncoderTest, TestInit) {
+    uidx = 0;
+    encoder_init();
+    EXPECT_EQ(pinIsInputHigh[0], true);
+    EXPECT_EQ(pinIsInputHigh[1], true);
+    EXPECT_EQ(uidx, 0);
+}
+
+TEST_F(EncoderTest, TestOneClockwise) {
+    uidx = 0;
+    encoder_init();
+    // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+}
+
+TEST_F(EncoderTest, TestOneCounterClockwise) {
+    uidx = 0;
+    encoder_init();
+    setAndRead(1, false);
+    setAndRead(0, false);
+    setAndRead(1, true);
+    setAndRead(0, true);
+
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, false);
+}
+
+TEST_F(EncoderTest, TestTwoClockwiseOneCC) {
+    uidx = 0;
+    encoder_init();
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+    setAndRead(1, false);
+    setAndRead(0, false);
+    setAndRead(1, true);
+    setAndRead(0, true);
+
+    EXPECT_EQ(uidx, 3);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+    EXPECT_EQ(updates[1].index, 0);
+    EXPECT_EQ(updates[1].clockwise, true);
+    EXPECT_EQ(updates[2].index, 0);
+    EXPECT_EQ(updates[2].clockwise, false);
+}
+
+TEST_F(EncoderTest, TestNoEarly) {
+    uidx = 0;
+    encoder_init();
+    // send 3 pulses. with resolution 4, that's not enough for a step.
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    EXPECT_EQ(uidx, 0);
+    // now send last pulse
+    setAndRead(1, true);
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+}
+
+TEST_F(EncoderTest, TestHalfway) {
+    uidx = 0;
+    encoder_init();
+    // go halfway
+    setAndRead(0, false);
+    setAndRead(1, false);
+    EXPECT_EQ(uidx, 0);
+    // back off
+    setAndRead(1, true);
+    setAndRead(0, true);
+    EXPECT_EQ(uidx, 0);
+    // go all the way
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+    // should result in 1 update
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+}
diff --git a/quantum/encoder/tests/encoder_tests_split.cpp b/quantum/encoder/tests/encoder_tests_split.cpp
new file mode 100644
index 00000000000..25e52c83f9d
--- /dev/null
+++ b/quantum/encoder/tests/encoder_tests_split.cpp
@@ -0,0 +1,143 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 "gtest/gtest.h"
+#include "gmock/gmock.h"
+#include <vector>
+#include <algorithm>
+#include <stdio.h>
+
+extern "C" {
+#include "encoder.h"
+#include "encoder/tests/mock_split.h"
+}
+
+struct update {
+    int8_t index;
+    bool   clockwise;
+};
+
+uint8_t uidx = 0;
+update  updates[32];
+
+bool isLeftHand;
+
+bool encoder_update_kb(uint8_t index, bool clockwise) {
+    if (!isLeftHand) {
+        // this method has no effect on slave half
+        printf("ignoring update on right hand (%d,%s)\n", index, clockwise ? "CW" : "CC");
+        return true;
+    }
+    updates[uidx % 32] = {index, clockwise};
+    uidx++;
+    return true;
+}
+
+bool setAndRead(pin_t pin, bool val) {
+    setPin(pin, val);
+    return encoder_read();
+}
+
+class EncoderTest : public ::testing::Test {
+   protected:
+    void SetUp() override {
+        uidx = 0;
+        for (int i = 0; i < 32; i++) {
+            pinIsInputHigh[i] = 0;
+            pins[i]           = 0;
+        }
+    }
+};
+
+TEST_F(EncoderTest, TestInitLeft) {
+    isLeftHand = true;
+    encoder_init();
+    EXPECT_EQ(pinIsInputHigh[0], true);
+    EXPECT_EQ(pinIsInputHigh[1], true);
+    EXPECT_EQ(pinIsInputHigh[2], false);
+    EXPECT_EQ(pinIsInputHigh[3], false);
+    EXPECT_EQ(uidx, 0);
+}
+
+TEST_F(EncoderTest, TestInitRight) {
+    isLeftHand = false;
+    encoder_init();
+    EXPECT_EQ(pinIsInputHigh[0], false);
+    EXPECT_EQ(pinIsInputHigh[1], false);
+    EXPECT_EQ(pinIsInputHigh[2], true);
+    EXPECT_EQ(pinIsInputHigh[3], true);
+    EXPECT_EQ(uidx, 0);
+}
+
+TEST_F(EncoderTest, TestOneClockwiseLeft) {
+    isLeftHand = true;
+    encoder_init();
+    // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+}
+
+TEST_F(EncoderTest, TestOneClockwiseRightSent) {
+    isLeftHand = false;
+    encoder_init();
+    // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
+    setAndRead(2, false);
+    setAndRead(3, false);
+    setAndRead(2, true);
+    setAndRead(3, true);
+
+    uint8_t slave_state[2] = {0};
+    encoder_state_raw(slave_state);
+
+    EXPECT_EQ((int8_t)slave_state[0], -1);
+}
+
+/* this test will not work after the previous test.
+ * this is due to encoder_value[1] already being set to -1 when simulating the right half.
+ * When we now receive this update acting as the left half, there is no change.
+ * This is hard to mock, as the static values inside encoder.c normally exist twice, once on each half,
+ * but here, they only exist once.
+ */
+
+// TEST_F(EncoderTest, TestOneClockwiseRightReceived) {
+//     isLeftHand = true;
+//     encoder_init();
+
+//     uint8_t slave_state[2] = {255, 0};
+//     encoder_update_raw(slave_state);
+
+//     EXPECT_EQ(uidx, 1);
+//     EXPECT_EQ(updates[0].index, 1);
+//     EXPECT_EQ(updates[0].clockwise, true);
+// }
+
+TEST_F(EncoderTest, TestOneCounterClockwiseRightReceived) {
+    isLeftHand = true;
+    encoder_init();
+
+    uint8_t slave_state[2] = {0, 0};
+    encoder_update_raw(slave_state);
+
+    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates[0].index, 1);
+    EXPECT_EQ(updates[0].clockwise, false);
+}
diff --git a/quantum/encoder/tests/mock.c b/quantum/encoder/tests/mock.c
new file mode 100644
index 00000000000..d0506a938f7
--- /dev/null
+++ b/quantum/encoder/tests/mock.c
@@ -0,0 +1,34 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 "mock.h"
+
+bool pins[32]           = {0};
+bool pinIsInputHigh[32] = {0};
+
+uint8_t mockSetPinInputHigh(pin_t pin) {
+    // dprintf("Setting pin %d input high.", pin);
+    pins[pin]           = true;
+    pinIsInputHigh[pin] = true;
+    return 0;
+}
+
+bool mockReadPin(pin_t pin) { return pins[pin]; }
+
+bool setPin(pin_t pin, bool val) {
+    pins[pin] = val;
+    return val;
+}
diff --git a/quantum/encoder/tests/mock.h b/quantum/encoder/tests/mock.h
new file mode 100644
index 00000000000..dbc25a08461
--- /dev/null
+++ b/quantum/encoder/tests/mock.h
@@ -0,0 +1,40 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 <stdint.h>
+#include <stdbool.h>
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0 }
+#define ENCODERS_PAD_B \
+    { 1 }
+
+typedef uint8_t pin_t;
+
+extern bool pins[];
+extern bool pinIsInputHigh[];
+
+#define setPinInputHigh(pin) (mockSetPinInputHigh(pin))
+#define readPin(pin) (mockReadPin(pin))
+
+uint8_t mockSetPinInputHigh(pin_t pin);
+
+bool mockReadPin(pin_t pin);
+
+bool setPin(pin_t pin, bool val);
diff --git a/quantum/encoder/tests/mock_split.c b/quantum/encoder/tests/mock_split.c
new file mode 100644
index 00000000000..68bf3af5992
--- /dev/null
+++ b/quantum/encoder/tests/mock_split.c
@@ -0,0 +1,36 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 "mock_split.h"
+
+bool pins[32]           = {0};
+bool pinIsInputHigh[32] = {0};
+
+uint8_t mockSetPinInputHigh(pin_t pin) {
+    // dprintf("Setting pin %d input high.", pin);
+    pins[pin]           = true;
+    pinIsInputHigh[pin] = true;
+    return 0;
+}
+
+bool mockReadPin(pin_t pin) { return pins[pin]; }
+
+bool setPin(pin_t pin, bool val) {
+    pins[pin] = val;
+    return val;
+}
+
+void last_encoder_activity_trigger(void) {}
diff --git a/quantum/encoder/tests/mock_split.h b/quantum/encoder/tests/mock_split.h
new file mode 100644
index 00000000000..0ae62652f97
--- /dev/null
+++ b/quantum/encoder/tests/mock_split.h
@@ -0,0 +1,48 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * 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 <stdint.h>
+#include <stdbool.h>
+
+#define SPLIT_KEYBOARD
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0 }
+#define ENCODERS_PAD_B \
+    { 1 }
+#define ENCODERS_PAD_A_RIGHT \
+    { 2 }
+#define ENCODERS_PAD_B_RIGHT \
+    { 3 }
+
+typedef uint8_t pin_t;
+extern bool     isLeftHand;
+void            encoder_state_raw(uint8_t* slave_state);
+void            encoder_update_raw(uint8_t* slave_state);
+
+extern bool pins[];
+extern bool pinIsInputHigh[];
+
+#define setPinInputHigh(pin) (mockSetPinInputHigh(pin))
+#define readPin(pin) (mockReadPin(pin))
+
+uint8_t mockSetPinInputHigh(pin_t pin);
+
+bool mockReadPin(pin_t pin);
+
+bool setPin(pin_t pin, bool val);
diff --git a/quantum/encoder/tests/rules.mk b/quantum/encoder/tests/rules.mk
new file mode 100644
index 00000000000..b826ce3aede
--- /dev/null
+++ b/quantum/encoder/tests/rules.mk
@@ -0,0 +1,13 @@
+encoder_DEFS := -DENCODER_MOCK_SINGLE
+
+encoder_SRC := \
+	$(QUANTUM_PATH)/encoder/tests/mock.c \
+	$(QUANTUM_PATH)/encoder/tests/encoder_tests.cpp \
+	$(QUANTUM_PATH)/encoder.c
+
+encoder_split_DEFS := -DENCODER_MOCK_SPLIT
+
+encoder_split_SRC := \
+	$(QUANTUM_PATH)/encoder/tests/mock_split.c \
+	$(QUANTUM_PATH)/encoder/tests/encoder_tests_split.cpp \
+	$(QUANTUM_PATH)/encoder.c
diff --git a/quantum/encoder/tests/testlist.mk b/quantum/encoder/tests/testlist.mk
new file mode 100644
index 00000000000..1be9f4a0548
--- /dev/null
+++ b/quantum/encoder/tests/testlist.mk
@@ -0,0 +1,3 @@
+TEST_LIST += \
+	encoder \
+	encoder_split