diff --git a/services/inputflinger/tests/Android.bp b/services/inputflinger/tests/Android.bp
index 9d200bd..76a7c19 100644
--- a/services/inputflinger/tests/Android.bp
+++ b/services/inputflinger/tests/Android.bp
@@ -47,6 +47,7 @@
         "InputReader_test.cpp",
         "InputFlingerService_test.cpp",
         "LatencyTracker_test.cpp",
+        "PreferStylusOverTouch_test.cpp",
         "TestInputListener.cpp",
         "UinputDevice.cpp",
         "UnwantedInteractionBlocker_test.cpp",
diff --git a/services/inputflinger/tests/PreferStylusOverTouch_test.cpp b/services/inputflinger/tests/PreferStylusOverTouch_test.cpp
new file mode 100644
index 0000000..70f40aa
--- /dev/null
+++ b/services/inputflinger/tests/PreferStylusOverTouch_test.cpp
@@ -0,0 +1,250 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+#include "../PreferStylusOverTouchBlocker.h"
+
+namespace android {
+
+constexpr int32_t TOUCH_DEVICE_ID = 3;
+constexpr int32_t STYLUS_DEVICE_ID = 4;
+
+constexpr int DOWN = AMOTION_EVENT_ACTION_DOWN;
+constexpr int MOVE = AMOTION_EVENT_ACTION_MOVE;
+constexpr int UP = AMOTION_EVENT_ACTION_UP;
+constexpr int CANCEL = AMOTION_EVENT_ACTION_CANCEL;
+constexpr int32_t TOUCHSCREEN = AINPUT_SOURCE_TOUCHSCREEN;
+constexpr int32_t STYLUS = AINPUT_SOURCE_STYLUS;
+
+struct PointerData {
+    float x;
+    float y;
+};
+
+static NotifyMotionArgs generateMotionArgs(nsecs_t downTime, nsecs_t eventTime, int32_t action,
+                                           const std::vector<PointerData>& points,
+                                           uint32_t source) {
+    size_t pointerCount = points.size();
+    if (action == DOWN || action == UP) {
+        EXPECT_EQ(1U, pointerCount) << "Actions DOWN and UP can only contain a single pointer";
+    }
+
+    PointerProperties pointerProperties[pointerCount];
+    PointerCoords pointerCoords[pointerCount];
+
+    const int32_t deviceId = isFromSource(source, TOUCHSCREEN) ? TOUCH_DEVICE_ID : STYLUS_DEVICE_ID;
+    const int32_t toolType = isFromSource(source, TOUCHSCREEN) ? AMOTION_EVENT_TOOL_TYPE_FINGER
+                                                               : AMOTION_EVENT_TOOL_TYPE_STYLUS;
+    for (size_t i = 0; i < pointerCount; i++) {
+        pointerProperties[i].clear();
+        pointerProperties[i].id = i;
+        pointerProperties[i].toolType = toolType;
+
+        pointerCoords[i].clear();
+        pointerCoords[i].setAxisValue(AMOTION_EVENT_AXIS_X, points[i].x);
+        pointerCoords[i].setAxisValue(AMOTION_EVENT_AXIS_Y, points[i].y);
+    }
+
+    // Currently, can't have STYLUS source without it also being a TOUCH source. Update the source
+    // accordingly.
+    if (isFromSource(source, STYLUS)) {
+        source |= TOUCHSCREEN;
+    }
+
+    // Define a valid motion event.
+    NotifyMotionArgs args(/* id */ 0, eventTime, 0 /*readTime*/, deviceId, source, 0 /*displayId*/,
+                          POLICY_FLAG_PASS_TO_USER, action, /* actionButton */ 0,
+                          /* flags */ 0, AMETA_NONE, /* buttonState */ 0,
+                          MotionClassification::NONE, AMOTION_EVENT_EDGE_FLAG_NONE, pointerCount,
+                          pointerProperties, pointerCoords, /* xPrecision */ 0, /* yPrecision */ 0,
+                          AMOTION_EVENT_INVALID_CURSOR_POSITION,
+                          AMOTION_EVENT_INVALID_CURSOR_POSITION, downTime, /* videoFrames */ {});
+
+    return args;
+}
+
+class PreferStylusOverTouchTest : public testing::Test {
+protected:
+    void assertNotBlocked(const NotifyMotionArgs& args) {
+        ftl::StaticVector<NotifyMotionArgs, 2> processedArgs = mBlocker.processMotion(args);
+        ASSERT_EQ(1u, processedArgs.size());
+        ASSERT_EQ(args, processedArgs[0]);
+    }
+
+    void assertDropped(const NotifyMotionArgs& args) {
+        ftl::StaticVector<NotifyMotionArgs, 2> processedArgs = mBlocker.processMotion(args);
+        ASSERT_TRUE(processedArgs.empty());
+    }
+
+    void assertCanceled(const NotifyMotionArgs& args,
+                        std::optional<NotifyMotionArgs> canceledArgs) {
+        ftl::StaticVector<NotifyMotionArgs, 2> processedArgs = mBlocker.processMotion(args);
+        ASSERT_EQ(2u, processedArgs.size());
+        NotifyMotionArgs& cancelEvent = processedArgs[0];
+        ASSERT_EQ(CANCEL, cancelEvent.action);
+        ASSERT_EQ(AMOTION_EVENT_FLAG_CANCELED, cancelEvent.flags & AMOTION_EVENT_FLAG_CANCELED);
+        ASSERT_TRUE(isFromSource(cancelEvent.source, TOUCHSCREEN));
+        ASSERT_FALSE(isFromSource(cancelEvent.source, STYLUS));
+
+        ASSERT_EQ(args, processedArgs[1]);
+    }
+
+private:
+    PreferStylusOverTouchBlocker mBlocker;
+};
+
+TEST_F(PreferStylusOverTouchTest, TouchGestureIsNotBlocked) {
+    NotifyMotionArgs args;
+
+    args = generateMotionArgs(0 /*downTime*/, 0 /*eventTime*/, DOWN, {{1, 2}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 1 /*eventTime*/, MOVE, {{1, 3}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 2 /*eventTime*/, UP, {{1, 3}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+}
+
+TEST_F(PreferStylusOverTouchTest, StylusGestureIsNotBlocked) {
+    NotifyMotionArgs args;
+
+    args = generateMotionArgs(0 /*downTime*/, 0 /*eventTime*/, DOWN, {{1, 2}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 1 /*eventTime*/, MOVE, {{1, 3}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 2 /*eventTime*/, UP, {{1, 3}}, STYLUS);
+    assertNotBlocked(args);
+}
+
+/**
+ * Existing touch gesture should be canceled when stylus goes down. There should be an ACTION_CANCEL
+ * event generated.
+ */
+TEST_F(PreferStylusOverTouchTest, TouchIsCanceledWhenStylusGoesDown) {
+    NotifyMotionArgs args;
+
+    args = generateMotionArgs(0 /*downTime*/, 0 /*eventTime*/, DOWN, {{1, 2}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 1 /*eventTime*/, MOVE, {{1, 3}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(3 /*downTime*/, 3 /*eventTime*/, DOWN, {{10, 30}}, STYLUS);
+    NotifyMotionArgs cancelArgs =
+            generateMotionArgs(0 /*downTime*/, 1 /*eventTime*/, CANCEL, {{1, 3}}, TOUCHSCREEN);
+    assertCanceled(args, cancelArgs);
+
+    // Both stylus and touch events continue. Stylus should be not blocked, and touch should be
+    // blocked
+    args = generateMotionArgs(3 /*downTime*/, 4 /*eventTime*/, MOVE, {{10, 31}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 5 /*eventTime*/, MOVE, {{1, 4}}, TOUCHSCREEN);
+    assertDropped(args);
+}
+
+/**
+ * New touch events should be simply blocked (dropped) when stylus is down. No CANCEL event should
+ * be generated.
+ */
+TEST_F(PreferStylusOverTouchTest, NewTouchIsBlockedWhenStylusIsDown) {
+    NotifyMotionArgs args;
+    constexpr nsecs_t stylusDownTime = 0;
+    constexpr nsecs_t touchDownTime = 1;
+
+    args = generateMotionArgs(stylusDownTime, 0 /*eventTime*/, DOWN, {{10, 30}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(touchDownTime, 1 /*eventTime*/, DOWN, {{1, 2}}, TOUCHSCREEN);
+    assertDropped(args);
+
+    // Stylus should continue to work
+    args = generateMotionArgs(stylusDownTime, 2 /*eventTime*/, MOVE, {{10, 31}}, STYLUS);
+    assertNotBlocked(args);
+
+    // Touch should continue to be blocked
+    args = generateMotionArgs(touchDownTime, 1 /*eventTime*/, MOVE, {{1, 3}}, TOUCHSCREEN);
+    assertDropped(args);
+
+    args = generateMotionArgs(0 /*downTime*/, 5 /*eventTime*/, MOVE, {{1, 4}}, TOUCHSCREEN);
+    assertDropped(args);
+}
+
+/**
+ * New touch events should be simply blocked (dropped) when stylus is down. No CANCEL event should
+ * be generated.
+ */
+TEST_F(PreferStylusOverTouchTest, NewTouchWorksAfterStylusIsLifted) {
+    NotifyMotionArgs args;
+    constexpr nsecs_t stylusDownTime = 0;
+    constexpr nsecs_t touchDownTime = 4;
+
+    // Stylus goes down and up
+    args = generateMotionArgs(stylusDownTime, 0 /*eventTime*/, DOWN, {{10, 30}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(stylusDownTime, 2 /*eventTime*/, MOVE, {{10, 31}}, STYLUS);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(stylusDownTime, 3 /*eventTime*/, UP, {{10, 31}}, STYLUS);
+    assertNotBlocked(args);
+
+    // New touch goes down. It should not be blocked
+    args = generateMotionArgs(touchDownTime, touchDownTime, DOWN, {{1, 2}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(touchDownTime, 5 /*eventTime*/, MOVE, {{1, 3}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+
+    args = generateMotionArgs(touchDownTime, 6 /*eventTime*/, UP, {{1, 3}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+}
+
+/**
+ * Once a touch gesture is canceled, it should continue to be canceled, even if the stylus has been
+ * lifted.
+ */
+TEST_F(PreferStylusOverTouchTest, AfterStylusIsLiftedCurrentTouchIsBlocked) {
+    NotifyMotionArgs args;
+    constexpr nsecs_t stylusDownTime = 0;
+    constexpr nsecs_t touchDownTime = 1;
+
+    assertNotBlocked(generateMotionArgs(stylusDownTime, 0 /*eventTime*/, DOWN, {{10, 30}}, STYLUS));
+
+    args = generateMotionArgs(touchDownTime, 1 /*eventTime*/, DOWN, {{1, 2}}, TOUCHSCREEN);
+    assertDropped(args);
+
+    // Lift the stylus
+    args = generateMotionArgs(stylusDownTime, 2 /*eventTime*/, UP, {{10, 30}}, STYLUS);
+    assertNotBlocked(args);
+
+    // Touch should continue to be blocked
+    args = generateMotionArgs(touchDownTime, 3 /*eventTime*/, MOVE, {{1, 3}}, TOUCHSCREEN);
+    assertDropped(args);
+
+    args = generateMotionArgs(touchDownTime, 4 /*eventTime*/, UP, {{1, 3}}, TOUCHSCREEN);
+    assertDropped(args);
+
+    // New touch should go through, though.
+    constexpr nsecs_t newTouchDownTime = 5;
+    args = generateMotionArgs(newTouchDownTime, 5 /*eventTime*/, DOWN, {{10, 20}}, TOUCHSCREEN);
+    assertNotBlocked(args);
+}
+
+} // namespace android