diff --git a/biometrics/face/aidl/default/Android.bp b/biometrics/face/aidl/default/Android.bp
index 7f66eca..48c929b 100644
--- a/biometrics/face/aidl/default/Android.bp
+++ b/biometrics/face/aidl/default/Android.bp
@@ -18,10 +18,43 @@
         "libbinder_ndk",
         "android.hardware.biometrics.face-V2-ndk",
         "android.hardware.biometrics.common-V2-ndk",
+        "android.hardware.biometrics.common.thread",
+        "android.hardware.biometrics.common.util",
     ],
     srcs: [
         "main.cpp",
         "Face.cpp",
+        "FakeFaceEngine.cpp",
         "Session.cpp",
     ],
+    static_libs: ["android.hardware.biometrics.face.VirtualProps"],
+}
+
+sysprop_library {
+    name: "android.hardware.biometrics.face.VirtualProps",
+    srcs: ["face.sysprop"],
+    property_owner: "Vendor",
+    vendor: true,
+}
+
+cc_test {
+    name: "android.hardware.biometrics.face.FakeFaceEngineTest",
+    srcs: [
+        "tests/FakeFaceEngineTest.cpp",
+        "FakeFaceEngine.cpp",
+    ],
+    shared_libs: [
+        "libbase",
+        "libbinder_ndk",
+    ],
+    static_libs: [
+        "android.hardware.biometrics.face.VirtualProps",
+        "android.hardware.biometrics.face-V2-ndk",
+        "android.hardware.biometrics.common-V2-ndk",
+        "android.hardware.keymaster-V3-ndk",
+        "android.hardware.biometrics.common.util",
+    ],
+    vendor: true,
+    test_suites: ["general-tests"],
+    require_root: true,
 }
diff --git a/biometrics/face/aidl/default/Face.cpp b/biometrics/face/aidl/default/Face.cpp
index aca3e13..652a7e1 100644
--- a/biometrics/face/aidl/default/Face.cpp
+++ b/biometrics/face/aidl/default/Face.cpp
@@ -17,12 +17,14 @@
 #include "Face.h"
 #include "Session.h"
 
+#include "FakeFaceEngine.h"
+
 namespace aidl::android::hardware::biometrics::face {
 
 const int kSensorId = 4;
-const common::SensorStrength kSensorStrength = common::SensorStrength::STRONG;
+const common::SensorStrength kSensorStrength = FakeFaceEngine::GetSensorStrength();
 const int kMaxEnrollmentsPerUser = 5;
-const FaceSensorType kSensorType = FaceSensorType::RGB;
+const FaceSensorType kSensorType = FakeFaceEngine::GetSensorType();
 const bool kHalControlsPreview = true;
 const std::string kHwComponentId = "faceSensor";
 const std::string kHardwareVersion = "vendor/model/revision";
@@ -69,7 +71,7 @@
 ndk::ScopedAStatus Face::createSession(int32_t /*sensorId*/, int32_t /*userId*/,
                                        const std::shared_ptr<ISessionCallback>& cb,
                                        std::shared_ptr<ISession>* return_val) {
-    *return_val = SharedRefBase::make<Session>(cb);
+    *return_val = SharedRefBase::make<Session>(std::make_unique<FakeFaceEngine>(), cb);
     return ndk::ScopedAStatus::ok();
 }
 
diff --git a/biometrics/face/aidl/default/FakeFaceEngine.cpp b/biometrics/face/aidl/default/FakeFaceEngine.cpp
new file mode 100644
index 0000000..0f088f4
--- /dev/null
+++ b/biometrics/face/aidl/default/FakeFaceEngine.cpp
@@ -0,0 +1,318 @@
+#include "FakeFaceEngine.h"
+
+#include <android-base/logging.h>
+
+#include <face.sysprop.h>
+
+#include "util/CancellationSignal.h"
+#include "util/Util.h"
+
+using namespace ::android::face::virt;
+
+namespace aidl::android::hardware::biometrics::face {
+
+FaceSensorType FakeFaceEngine::GetSensorType() {
+    std::string type = FaceHalProperties::type().value_or("");
+    if (type == "IR") {
+        return FaceSensorType::IR;
+    } else {
+        FaceHalProperties::type("RGB");
+        return FaceSensorType::RGB;
+    }
+}
+
+common::SensorStrength FakeFaceEngine::GetSensorStrength() {
+    std::string strength = FaceHalProperties::strength().value_or("");
+    if (strength == "convenience") {
+        return common::SensorStrength::CONVENIENCE;
+    } else if (strength == "weak") {
+        return common::SensorStrength::WEAK;
+    } else {
+        FaceHalProperties::strength("strong");
+        return common::SensorStrength::STRONG;
+    }
+}
+
+void FakeFaceEngine::generateChallengeImpl(ISessionCallback* cb) {
+    BEGIN_OP(0);
+    std::uniform_int_distribution<int64_t> dist;
+    auto challenge = dist(mRandom);
+    FaceHalProperties::challenge(challenge);
+    cb->onChallengeGenerated(challenge);
+}
+
+void FakeFaceEngine::revokeChallengeImpl(ISessionCallback* cb, int64_t challenge) {
+    BEGIN_OP(0);
+    FaceHalProperties::challenge({});
+    cb->onChallengeRevoked(challenge);
+}
+void FakeFaceEngine::getEnrollmentConfigImpl(ISessionCallback* /*cb*/,
+                                             std::vector<EnrollmentStageConfig>* /*return_val*/) {}
+void FakeFaceEngine::enrollImpl(ISessionCallback* cb, const keymaster::HardwareAuthToken& hat,
+                                EnrollmentType /*enrollmentType*/,
+                                const std::vector<Feature>& /*features*/,
+                                const std::future<void>& cancel) {
+    BEGIN_OP(FaceHalProperties::operation_start_enroll_latency().value_or(0));
+    // format is "<id>,<bucket_id>:<delay>:<succeeds>,<bucket_id>:<delay>:<succeeds>...
+    auto nextEnroll = FaceHalProperties::next_enrollment().value_or("");
+    // Erase the next enrollment
+    FaceHalProperties::next_enrollment({});
+
+    AuthenticationFrame frame;
+    frame.data.acquiredInfo = AcquiredInfo::START;
+    frame.data.vendorCode = 0;
+    cb->onAuthenticationFrame(frame);
+
+    // Do proper HAT verification in the real implementation.
+    if (hat.mac.empty()) {
+        LOG(ERROR) << "Fail: hat";
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorError */);
+        return;
+    }
+
+    if (FaceHalProperties::operation_enroll_fails().value_or(false)) {
+        LOG(ERROR) << "Fail: operation_enroll_fails";
+        cb->onError(Error::VENDOR, 0 /* vendorError */);
+        return;
+    }
+
+    auto parts = Util::split(nextEnroll, ",");
+    if (parts.size() < 2) {
+        LOG(ERROR) << "Fail: invalid next_enrollment for : " << nextEnroll;
+        cb->onError(Error::VENDOR, 0 /* vendorError */);
+        return;
+    }
+
+    auto enrollmentId = std::stoi(parts[0]);
+    const int numBuckets = parts.size() - 1;
+    for (size_t i = 1; i < parts.size(); i++) {
+        auto enrollHit = Util::split(parts[i], ":");
+        if (enrollHit.size() != 3) {
+            LOG(ERROR) << "Error when unpacking enrollment hit: " << parts[i];
+            cb->onError(Error::VENDOR, 0 /* vendorError */);
+        }
+        std::string bucket = enrollHit[0];
+        std::string delay = enrollHit[1];
+        std::string succeeds = enrollHit[2];
+
+        SLEEP_MS(std::stoi(delay));
+
+        if (shouldCancel(cancel)) {
+            LOG(ERROR) << "Fail: cancel";
+            cb->onError(Error::CANCELED, 0 /* vendorCode */);
+            return;
+        }
+
+        if (!IS_TRUE(succeeds)) {  // end and failed
+            LOG(ERROR) << "Fail: requested by caller: " << parts[i];
+            cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
+            return;
+        }
+
+        EnrollmentFrame frame;
+
+        frame.data.acquiredInfo = AcquiredInfo::GOOD;
+        frame.data.vendorCode = 0;
+        cb->onEnrollmentFrame(frame);
+
+        frame.data.acquiredInfo = AcquiredInfo::VENDOR;
+        frame.data.vendorCode = std::stoi(bucket);
+        cb->onEnrollmentFrame(frame);
+
+        int remainingBuckets = numBuckets - i;
+        if (remainingBuckets > 0) {
+            cb->onEnrollmentProgress(enrollmentId, remainingBuckets);
+        }
+    }
+
+    auto enrollments = FaceHalProperties::enrollments();
+    enrollments.push_back(enrollmentId);
+    FaceHalProperties::enrollments(enrollments);
+    LOG(INFO) << "enrolled : " << enrollmentId;
+    cb->onEnrollmentProgress(enrollmentId, 0);
+}
+
+void FakeFaceEngine::authenticateImpl(ISessionCallback* cb, int64_t /*operationId*/,
+                                      const std::future<void>& cancel) {
+    BEGIN_OP(FaceHalProperties::operation_authenticate_latency().value_or(0));
+
+    // Signal to the framework that we have begun authenticating.
+    AuthenticationFrame frame;
+    frame.data.acquiredInfo = AcquiredInfo::START;
+    frame.data.vendorCode = 0;
+    cb->onAuthenticationFrame(frame);
+
+    // Also signal that we have opened the camera.
+    frame = {};
+    frame.data.acquiredInfo = AcquiredInfo::FIRST_FRAME_RECEIVED;
+    frame.data.vendorCode = 0;
+    cb->onAuthenticationFrame(frame);
+
+    auto now = Util::getSystemNanoTime();
+    int64_t duration = FaceHalProperties::operation_authenticate_duration().value_or(0);
+    if (duration > 0) {
+        do {
+            SLEEP_MS(5);
+        } while (!Util::hasElapsed(now, duration));
+    }
+
+    if (FaceHalProperties::operation_authenticate_fails().value_or(false)) {
+        LOG(ERROR) << "Fail: operation_authenticate_fails";
+        cb->onError(Error::VENDOR, 0 /* vendorError */);
+        return;
+    }
+
+    if (FaceHalProperties::lockout().value_or(false)) {
+        LOG(ERROR) << "Fail: lockout";
+        cb->onLockoutPermanent();
+        cb->onError(Error::HW_UNAVAILABLE, 0 /* vendorError */);
+        return;
+    }
+
+    if (shouldCancel(cancel)) {
+        LOG(ERROR) << "Fail: cancel";
+        cb->onError(Error::CANCELED, 0 /* vendorCode */);
+        return;
+    }
+
+    auto id = FaceHalProperties::enrollment_hit().value_or(0);
+    auto enrolls = FaceHalProperties::enrollments();
+    auto isEnrolled = std::find(enrolls.begin(), enrolls.end(), id) != enrolls.end();
+    if (id < 0 || !isEnrolled) {
+        LOG(ERROR) << (isEnrolled ? "invalid enrollment hit" : "Fail: not enrolled");
+        cb->onAuthenticationFailed();
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorError */);
+        return;
+    }
+
+    cb->onAuthenticationSucceeded(id, {} /* hat */);
+}
+
+void FakeFaceEngine::detectInteractionImpl(ISessionCallback* cb, const std::future<void>& cancel) {
+    BEGIN_OP(FaceHalProperties::operation_detect_interaction_latency().value_or(0));
+
+    if (FaceHalProperties::operation_detect_interaction_fails().value_or(false)) {
+        LOG(ERROR) << "Fail: operation_detect_interaction_fails";
+        cb->onError(Error::VENDOR, 0 /* vendorError */);
+        return;
+    }
+
+    if (shouldCancel(cancel)) {
+        LOG(ERROR) << "Fail: cancel";
+        cb->onError(Error::CANCELED, 0 /* vendorCode */);
+        return;
+    }
+
+    auto id = FaceHalProperties::enrollment_hit().value_or(0);
+    auto enrolls = FaceHalProperties::enrollments();
+    auto isEnrolled = std::find(enrolls.begin(), enrolls.end(), id) != enrolls.end();
+    if (id <= 0 || !isEnrolled) {
+        LOG(ERROR) << "Fail: not enrolled";
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorError */);
+        return;
+    }
+
+    cb->onInteractionDetected();
+}
+
+void FakeFaceEngine::enumerateEnrollmentsImpl(ISessionCallback* cb) {
+    BEGIN_OP(0);
+    std::vector<int32_t> enrollments;
+    for (const auto& enrollmentId : FaceHalProperties::enrollments()) {
+        if (enrollmentId) {
+            enrollments.push_back(*enrollmentId);
+        }
+    }
+    cb->onEnrollmentsEnumerated(enrollments);
+}
+
+void FakeFaceEngine::removeEnrollmentsImpl(ISessionCallback* cb,
+                                           const std::vector<int32_t>& enrollmentIds) {
+    BEGIN_OP(0);
+
+    std::vector<std::optional<int32_t>> newEnrollments;
+    for (const auto& enrollment : FaceHalProperties::enrollments()) {
+        auto id = enrollment.value_or(0);
+        if (std::find(enrollmentIds.begin(), enrollmentIds.end(), id) == enrollmentIds.end()) {
+            newEnrollments.emplace_back(id);
+        }
+    }
+    FaceHalProperties::enrollments(newEnrollments);
+    cb->onEnrollmentsRemoved(enrollmentIds);
+}
+
+void FakeFaceEngine::getFeaturesImpl(ISessionCallback* cb) {
+    BEGIN_OP(0);
+
+    if (FaceHalProperties::enrollments().empty()) {
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
+        return;
+    }
+
+    std::vector<Feature> featuresToReturn = {};
+    for (const auto& feature : FaceHalProperties::features()) {
+        if (feature) {
+            featuresToReturn.push_back((Feature)(*feature));
+        }
+    }
+    cb->onFeaturesRetrieved(featuresToReturn);
+}
+
+void FakeFaceEngine::setFeatureImpl(ISessionCallback* cb, const keymaster::HardwareAuthToken& hat,
+                                    Feature feature, bool enabled) {
+    BEGIN_OP(0);
+
+    if (FaceHalProperties::enrollments().empty()) {
+        LOG(ERROR) << "Unable to set feature, enrollments are empty";
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
+        return;
+    }
+
+    if (hat.mac.empty()) {
+        LOG(ERROR) << "Unable to set feature, invalid hat";
+        cb->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
+        return;
+    }
+
+    auto features = FaceHalProperties::features();
+
+    auto itr = std::find_if(features.begin(), features.end(), [feature](const auto& theFeature) {
+        return *theFeature == (int)feature;
+    });
+
+    if (!enabled && (itr != features.end())) {
+        features.erase(itr);
+    } else if (enabled && (itr == features.end())) {
+        features.push_back((int)feature);
+    }
+
+    FaceHalProperties::features(features);
+    cb->onFeatureSet(feature);
+}
+
+void FakeFaceEngine::getAuthenticatorIdImpl(ISessionCallback* cb) {
+    BEGIN_OP(0);
+    // If this is a weak HAL return 0 per the spec.
+    if (GetSensorStrength() != common::SensorStrength::STRONG) {
+        cb->onAuthenticatorIdRetrieved(0);
+    } else {
+        cb->onAuthenticatorIdRetrieved(FaceHalProperties::authenticator_id().value_or(0));
+    }
+}
+
+void FakeFaceEngine::invalidateAuthenticatorIdImpl(ISessionCallback* cb) {
+    BEGIN_OP(0);
+    int64_t authenticatorId = FaceHalProperties::authenticator_id().value_or(0);
+    int64_t newId = authenticatorId + 1;
+    FaceHalProperties::authenticator_id(newId);
+    cb->onAuthenticatorIdInvalidated(newId);
+}
+
+void FakeFaceEngine::resetLockoutImpl(ISessionCallback* cb,
+                                      const keymaster::HardwareAuthToken& /*hat*/) {
+    BEGIN_OP(0);
+    FaceHalProperties::lockout(false);
+    cb->onLockoutCleared();
+}
+
+}  // namespace aidl::android::hardware::biometrics::face
\ No newline at end of file
diff --git a/biometrics/face/aidl/default/FakeFaceEngine.h b/biometrics/face/aidl/default/FakeFaceEngine.h
new file mode 100644
index 0000000..edb54ce
--- /dev/null
+++ b/biometrics/face/aidl/default/FakeFaceEngine.h
@@ -0,0 +1,65 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <aidl/android/hardware/biometrics/common/SensorStrength.h>
+#include <aidl/android/hardware/biometrics/face/BnSession.h>
+#include <aidl/android/hardware/biometrics/face/FaceSensorType.h>
+#include <aidl/android/hardware/biometrics/face/ISessionCallback.h>
+
+#include <random>
+
+#include <future>
+#include <vector>
+
+namespace aidl::android::hardware::biometrics::face {
+
+namespace face = aidl::android::hardware::biometrics::face;
+namespace common = aidl::android::hardware::biometrics::common;
+namespace keymaster = aidl::android::hardware::keymaster;
+
+using aidl::android::hardware::common::NativeHandle;
+// A fake engine that is backed by system properties instead of hardware.
+class FakeFaceEngine {
+  public:
+    FakeFaceEngine() : mRandom(std::mt19937::default_seed) {}
+
+    static face::FaceSensorType GetSensorType();
+    static common::SensorStrength GetSensorStrength();
+    void generateChallengeImpl(ISessionCallback* cb);
+    void revokeChallengeImpl(ISessionCallback* cb, int64_t challenge);
+    void getEnrollmentConfigImpl(ISessionCallback* cb,
+                                 std::vector<EnrollmentStageConfig>* return_val);
+    void enrollImpl(ISessionCallback* cb, const keymaster::HardwareAuthToken& hat,
+                    EnrollmentType enrollmentType, const std::vector<Feature>& features,
+                    const std::future<void>& cancel);
+    void authenticateImpl(ISessionCallback* cb, int64_t operationId,
+                          const std::future<void>& cancel);
+    void detectInteractionImpl(ISessionCallback* cb, const std::future<void>& cancel);
+    void enumerateEnrollmentsImpl(ISessionCallback* cb);
+    void removeEnrollmentsImpl(ISessionCallback* cb, const std::vector<int32_t>& enrollmentIds);
+    void getFeaturesImpl(ISessionCallback* cb);
+    void setFeatureImpl(ISessionCallback* cb, const keymaster::HardwareAuthToken& hat,
+                        Feature feature, bool enabled);
+    void getAuthenticatorIdImpl(ISessionCallback* cb);
+    void invalidateAuthenticatorIdImpl(ISessionCallback* cb);
+    void resetLockoutImpl(ISessionCallback* cb, const keymaster::HardwareAuthToken& /*hat*/);
+
+    std::mt19937 mRandom;
+};
+
+}  // namespace aidl::android::hardware::biometrics::face
\ No newline at end of file
diff --git a/biometrics/face/aidl/default/README.md b/biometrics/face/aidl/default/README.md
new file mode 100644
index 0000000..1655973
--- /dev/null
+++ b/biometrics/face/aidl/default/README.md
@@ -0,0 +1,77 @@
+# Virtual Face HAL
+
+This is a virtual HAL implementation that is backed by system properties
+instead of actual hardware. It's intended for testing and UI development
+on debuggable builds to allow devices to masquerade as alternative device
+types and for emulators.
+
+## Device Selection
+
+You can either run the FakeFaceEngine on a [real device](#actual-device) or a [virtual device/cuttlefish](#getting-started-on-a-virtual-device-cuttlefish). This document should
+help you to get started on either one.
+
+After setting up a device, go ahead and try out [enrolling](#enrolling) & [authenticating](#authenticating)
+
+### Getting started on a Virtual Device (cuttlefish)
+
+
+Note, I'm running this via a cloudtop virtual device.
+
+1. Setup cuttlefish on cloudtop, See [this](https://g3doc.corp.google.com/company/teams/android/teampages/acloud/getting_started.md?cl=head) for more details.
+2. acloud create --local-image
+3. Enter in the shell command to disable hidl
+
+```shell
+$ adb root
+$ adb shell settings put secure com.android.server.biometrics.AuthService.hidlDisabled 1
+$ adb reboot
+```
+4. You should now be able to do fake enrollments and authentications (as seen down below)
+
+### Actual Device
+
+1. Modify your real devices make file (I.E. vendor/google/products/{YOUR_DEVICE}.mk)
+2. Ensure that there is no other face HAL that is being included by the device
+3. Add the following
+```
+PRODUCT_COPY_FILES += \
+    frameworks/native/data/etc/android.hardware.biometrics.face.xml:$(TARGET_COPY_OUT_PRODUCT)/etc/permissions/android.hardware.biometrics.face.xml
+
+PRODUCT_PACKAGES += \
+    android.hardware.biometrics.face-service.example \
+
+```
+4. Now build and flash m -j120 && flash
+5. Run the following commands
+
+```shell
+# This is a temporary workaround
+$ adb root
+$ adb shell setprop persist.vendor.face.virtual.type RGB
+$ adb shell setprop persist.vendor.face.virtual.strength strong
+$ adb shell locksettings set-pin 0000
+$ adb reboot
+```
+
+## Enrolling
+
+```shell
+# authenticar_id,bucket_id:duration:(true|false)....
+$ adb shell setprop vendor.face.virtual.next_enrollment 1,0:500:true,5:250:true,10:150:true,15:500:true
+$ adb shell am start -n com.android.settings/.biometrics.face.FaceEnrollIntroduction
+# If you would like to get rid of the enrollment, run the follwoing command
+$ adb shell setprop persist.vendor.face.virtual.enrollments \"\"
+```
+
+## Authenticating
+
+```shell
+# If enrollment hasn't been setup
+$ adb shell setprop persist.vendor.face.virtual.enrollments 1
+$ adb shell cmd face sync
+# After enrollment has been setup
+$ adb shell setprop vendor.face.virtual.operation_authenticate_duration 800
+$ adb shell setprop vendor.face.virtual.enrollment_hit 1
+# Power button press to simulate auth
+$ adb shell input keyevent 26
+```
diff --git a/biometrics/face/aidl/default/Session.cpp b/biometrics/face/aidl/default/Session.cpp
index 984a1a9..1188459 100644
--- a/biometrics/face/aidl/default/Session.cpp
+++ b/biometrics/face/aidl/default/Session.cpp
@@ -14,139 +14,135 @@
  * limitations under the License.
  */
 
-#include <aidl/android/hardware/biometrics/common/BnCancellationSignal.h>
 #include <android-base/logging.h>
 
 #include "Session.h"
 
 namespace aidl::android::hardware::biometrics::face {
 
-class CancellationSignal : public common::BnCancellationSignal {
-  private:
-    std::shared_ptr<ISessionCallback> cb_;
+constexpr size_t MAX_WORKER_QUEUE_SIZE = 5;
 
-  public:
-    explicit CancellationSignal(std::shared_ptr<ISessionCallback> cb) : cb_(std::move(cb)) {}
-
-    ndk::ScopedAStatus cancel() override {
-        cb_->onError(Error::CANCELED, 0 /* vendorCode */);
-        return ndk::ScopedAStatus::ok();
-    }
-};
-
-Session::Session(std::shared_ptr<ISessionCallback> cb)
-    : cb_(std::move(cb)), mRandom(std::mt19937::default_seed) {}
+Session::Session(std::unique_ptr<FakeFaceEngine> engine, std::shared_ptr<ISessionCallback> cb)
+    : mEngine(std::move(engine)), mCb(std::move(cb)), mRandom(std::mt19937::default_seed) {
+    mThread = std::make_unique<WorkerThread>(MAX_WORKER_QUEUE_SIZE);
+}
 
 ndk::ScopedAStatus Session::generateChallenge() {
     LOG(INFO) << "generateChallenge";
-    if (cb_) {
-        std::uniform_int_distribution<int64_t> dist;
-        auto challenge = dist(mRandom);
-        cb_->onChallengeGenerated(challenge);
-    }
+    mThread->schedule(Callable::from([this] { mEngine->generateChallengeImpl(mCb.get()); }));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::revokeChallenge(int64_t challenge) {
     LOG(INFO) << "revokeChallenge";
-    if (cb_) {
-        cb_->onChallengeRevoked(challenge);
-    }
+    mThread->schedule(Callable::from(
+            [this, challenge] { mEngine->revokeChallengeImpl(mCb.get(), challenge); }));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::getEnrollmentConfig(EnrollmentType /*enrollmentType*/,
-                                                std::vector<EnrollmentStageConfig>* return_val) {
-    *return_val = {};
+ndk::ScopedAStatus Session::getEnrollmentConfig(
+        EnrollmentType /*enrollmentType*/, std::vector<EnrollmentStageConfig>* cancellationSignal) {
+    *cancellationSignal = {};
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::enroll(
-        const keymaster::HardwareAuthToken& /*hat*/, EnrollmentType /*enrollmentType*/,
-        const std::vector<Feature>& /*features*/,
-        const std::optional<NativeHandle>& /*previewSurface*/,
-        std::shared_ptr<biometrics::common::ICancellationSignal>* /*return_val*/) {
+        const keymaster::HardwareAuthToken& hat, EnrollmentType enrollmentType,
+        const std::vector<Feature>& features, const std::optional<NativeHandle>& /*previewSurface*/,
+        std::shared_ptr<biometrics::common::ICancellationSignal>* cancellationSignal) {
     LOG(INFO) << "enroll";
-    if (cb_) {
-        cb_->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorError */);
-    }
+    std::promise<void> cancellationPromise;
+    auto cancFuture = cancellationPromise.get_future();
+
+    mThread->schedule(Callable::from(
+            [this, hat, enrollmentType, features, cancFuture = std::move(cancFuture)] {
+                mEngine->enrollImpl(mCb.get(), hat, enrollmentType, features, cancFuture);
+            }));
+
+    *cancellationSignal = SharedRefBase::make<CancellationSignal>(std::move(cancellationPromise));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::authenticate(int64_t /*keystoreOperationId*/,
-                                         std::shared_ptr<common::ICancellationSignal>* return_val) {
+ndk::ScopedAStatus Session::authenticate(
+        int64_t keystoreOperationId,
+        std::shared_ptr<common::ICancellationSignal>* cancellationSignal) {
     LOG(INFO) << "authenticate";
-    if (cb_) {
-        cb_->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
-    }
-    *return_val = SharedRefBase::make<CancellationSignal>(cb_);
+    std::promise<void> cancellationPromise;
+    auto cancFuture = cancellationPromise.get_future();
+
+    mThread->schedule(
+            Callable::from([this, keystoreOperationId, cancFuture = std::move(cancFuture)] {
+                mEngine->authenticateImpl(mCb.get(), keystoreOperationId, cancFuture);
+            }));
+
+    *cancellationSignal = SharedRefBase::make<CancellationSignal>(std::move(cancellationPromise));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::detectInteraction(
-        std::shared_ptr<common::ICancellationSignal>* /*return_val*/) {
+        std::shared_ptr<common::ICancellationSignal>* cancellationSignal) {
     LOG(INFO) << "detectInteraction";
+    std::promise<void> cancellationPromise;
+    auto cancFuture = cancellationPromise.get_future();
+
+    mThread->schedule(Callable::from([this, cancFuture = std::move(cancFuture)] {
+        mEngine->detectInteractionImpl(mCb.get(), cancFuture);
+    }));
+
+    *cancellationSignal = SharedRefBase::make<CancellationSignal>(std::move(cancellationPromise));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::enumerateEnrollments() {
     LOG(INFO) << "enumerateEnrollments";
-    if (cb_) {
-        cb_->onEnrollmentsEnumerated(std::vector<int32_t>());
-    }
+    mThread->schedule(Callable::from([this] { mEngine->enumerateEnrollmentsImpl(mCb.get()); }));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::removeEnrollments(const std::vector<int32_t>& /*enrollmentIds*/) {
+ndk::ScopedAStatus Session::removeEnrollments(const std::vector<int32_t>& enrollmentIds) {
     LOG(INFO) << "removeEnrollments";
-    if (cb_) {
-        cb_->onEnrollmentsRemoved(std::vector<int32_t>());
-    }
+    mThread->schedule(Callable::from(
+            [this, enrollmentIds] { mEngine->removeEnrollmentsImpl(mCb.get(), enrollmentIds); }));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::getFeatures() {
     LOG(INFO) << "getFeatures";
-    if (cb_) {
-        // Must error out with UNABLE_TO_PROCESS when no faces are enrolled.
-        cb_->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
-    }
+    mThread->schedule(Callable::from([this] { mEngine->getFeaturesImpl(mCb.get()); }));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::setFeature(const keymaster::HardwareAuthToken& /*hat*/,
-                                       Feature /*feature*/, bool /*enabled*/) {
+ndk::ScopedAStatus Session::setFeature(const keymaster::HardwareAuthToken& hat, Feature feature,
+                                       bool enabled) {
     LOG(INFO) << "setFeature";
+    mThread->schedule(Callable::from([this, hat, feature, enabled] {
+        mEngine->setFeatureImpl(mCb.get(), hat, feature, enabled);
+    }));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::getAuthenticatorId() {
     LOG(INFO) << "getAuthenticatorId";
-    if (cb_) {
-        cb_->onAuthenticatorIdRetrieved(0 /* authenticatorId */);
-    }
+    mThread->schedule(Callable::from([this] { mEngine->getAuthenticatorIdImpl(mCb.get()); }));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::invalidateAuthenticatorId() {
     LOG(INFO) << "invalidateAuthenticatorId";
-    if (cb_) {
-        cb_->onAuthenticatorIdInvalidated(0);
-    }
+    mThread->schedule(
+            Callable::from([this] { mEngine->invalidateAuthenticatorIdImpl(mCb.get()); }));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::resetLockout(const keymaster::HardwareAuthToken& /*hat*/) {
+ndk::ScopedAStatus Session::resetLockout(const keymaster::HardwareAuthToken& hat) {
     LOG(INFO) << "resetLockout";
-    if (cb_) {
-        cb_->onLockoutCleared();
-    }
+    mThread->schedule(Callable::from([this, hat] { mEngine->resetLockoutImpl(mCb.get(), hat); }));
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::close() {
-    if (cb_) {
-        cb_->onSessionClosed();
+    if (mCb) {
+        mCb->onSessionClosed();
     }
     return ndk::ScopedAStatus::ok();
 }
diff --git a/biometrics/face/aidl/default/Session.h b/biometrics/face/aidl/default/Session.h
index 9db17d2..7ca6a1f 100644
--- a/biometrics/face/aidl/default/Session.h
+++ b/biometrics/face/aidl/default/Session.h
@@ -21,6 +21,10 @@
 #include <aidl/android/hardware/biometrics/face/BnSession.h>
 #include <aidl/android/hardware/biometrics/face/ISessionCallback.h>
 
+#include "FakeFaceEngine.h"
+#include "thread/WorkerThread.h"
+#include "util/CancellationSignal.h"
+
 namespace aidl::android::hardware::biometrics::face {
 
 namespace common = aidl::android::hardware::biometrics::common;
@@ -30,7 +34,7 @@
 
 class Session : public BnSession {
   public:
-    explicit Session(std::shared_ptr<ISessionCallback> cb);
+    explicit Session(std::unique_ptr<FakeFaceEngine> engine, std::shared_ptr<ISessionCallback> cb);
 
     ndk::ScopedAStatus generateChallenge() override;
 
@@ -85,8 +89,11 @@
     ndk::ScopedAStatus onContextChanged(const common::OperationContext& context) override;
 
   private:
-    std::shared_ptr<ISessionCallback> cb_;
+    std::unique_ptr<FakeFaceEngine> mEngine;
+    std::shared_ptr<ISessionCallback> mCb;
     std::mt19937 mRandom;
+    std::unique_ptr<WorkerThread> mThread;
+    std::shared_ptr<CancellationSignal> mCancellationSignal;
 };
 
 }  // namespace aidl::android::hardware::biometrics::face
diff --git a/biometrics/face/aidl/default/api/android.hardware.biometrics.face.VirtualProps-current.txt b/biometrics/face/aidl/default/api/android.hardware.biometrics.face.VirtualProps-current.txt
new file mode 100644
index 0000000..9548920
--- /dev/null
+++ b/biometrics/face/aidl/default/api/android.hardware.biometrics.face.VirtualProps-current.txt
@@ -0,0 +1,98 @@
+props {
+  owner: Vendor
+  module: "android.face.virt.FaceHalProperties"
+  prop {
+    api_name: "authenticator_id"
+    type: Long
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.authenticator_id"
+  }
+  prop {
+    api_name: "challenge"
+    type: Long
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.challenge"
+  }
+  prop {
+    api_name: "enrollment_hit"
+    type: Integer
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.enrollment_hit"
+  }
+  prop {
+    api_name: "enrollments"
+    type: IntegerList
+    access: ReadWrite
+    prop_name: "persist.vendor.face.virtual.enrollments"
+  }
+  prop {
+    api_name: "features"
+    type: IntegerList
+    access: ReadWrite
+    prop_name: "persist.vendor.face.virtual.features"
+  }
+  prop {
+    api_name: "lockout"
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.lockout"
+  }
+  prop {
+    api_name: "next_enrollment"
+    type: String
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.next_enrollment"
+  }
+  prop {
+    api_name: "operation_authenticate_duration"
+    type: Integer
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_authenticate_duration"
+  }
+  prop {
+    api_name: "operation_authenticate_fails"
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_authenticate_fails"
+  }
+  prop {
+    api_name: "operation_authenticate_latency"
+    type: Integer
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_authenticate_latency"
+  }
+  prop {
+    api_name: "operation_detect_interaction_fails"
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_detect_interaction_fails"
+  }
+  prop {
+    api_name: "operation_detect_interaction_latency"
+    type: Integer
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_detect_interaction_latency"
+  }
+  prop {
+    api_name: "operation_enroll_fails"
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_enroll_fails"
+  }
+  prop {
+    api_name: "operation_start_enroll_latency"
+    type: Integer
+    access: ReadWrite
+    prop_name: "vendor.face.virtual.operation_start_enroll_latency"
+  }
+  prop {
+    api_name: "strength"
+    type: String
+    access: ReadWrite
+    prop_name: "persist.vendor.face.virtual.strength"
+    enum_values: "convenience|weak|strong"
+  }
+  prop {
+    api_name: "type"
+    type: String
+    access: ReadWrite
+    prop_name: "persist.vendor.face.virtual.type"
+    enum_values: "IR|RGB"
+  }
+}
diff --git a/biometrics/face/aidl/default/face.sysprop b/biometrics/face/aidl/default/face.sysprop
new file mode 100644
index 0000000..6b0f37f
--- /dev/null
+++ b/biometrics/face/aidl/default/face.sysprop
@@ -0,0 +1,159 @@
+# face.sysprop
+# module becomes static class (Java) / namespace (C++) for serving API
+module: "android.face.virt.FaceHalProperties"
+owner: Vendor
+
+# type of face sensor
+prop {
+    prop_name: "persist.vendor.face.virtual.type"
+    type: String
+    scope: Public
+    access: ReadWrite
+    enum_values: "IR|RGB"
+    api_name: "type"
+}
+
+# the strength of the sensor
+prop {
+    prop_name: "persist.vendor.face.virtual.strength"
+    type: String
+    scope: Public
+    access: ReadWrite
+    enum_values: "convenience|weak|strong"
+    api_name: "strength"
+}
+
+# ids of current enrollments
+prop {
+    prop_name: "persist.vendor.face.virtual.enrollments"
+    type: IntegerList
+    scope: Public
+    access: ReadWrite
+    api_name: "enrollments"
+}
+
+# List of features
+prop {
+    prop_name: "persist.vendor.face.virtual.features"
+    type: IntegerList
+    scope: Public
+    access: ReadWrite
+    api_name: "features"
+}
+
+# authenticate and detectInteraction will succeed with this
+# enrollment id, when present, otherwise they will error
+prop {
+    prop_name: "vendor.face.virtual.enrollment_hit"
+    type: Integer
+    scope: Public
+    access: ReadWrite
+    api_name: "enrollment_hit"
+}
+
+# The initial latency for enrollment
+prop {
+    prop_name: "vendor.face.virtual.operation_start_enroll_latency"
+    type: Integer
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_start_enroll_latency"
+}
+
+# the next enrollment in the format:
+# "<id>,<bucket_id>:<delay>:<succeeds>,<bucket_id>..."
+# for example: "0:1,0:100:1,1:200:1" indicating that bucket 0 took
+# 50 milliseconds, bucket 1 took 100 milliseconds, bucket 2 took 200 milliseconds.
+# Note that it is up to the configuration to determine how many buckets are required
+# to complete an enrollment
+prop {
+    prop_name: "vendor.face.virtual.next_enrollment"
+    type: String
+    scope: Public
+    access: ReadWrite
+    api_name: "next_enrollment"
+}
+
+# value for getAuthenticatorId or 0
+prop {
+    prop_name: "vendor.face.virtual.authenticator_id"
+    type: Long
+    scope: Public
+    access: ReadWrite
+    api_name: "authenticator_id"
+}
+
+# value for generateChallenge
+prop {
+    prop_name: "vendor.face.virtual.challenge"
+    type: Long
+    scope: Public
+    access: ReadWrite
+    api_name: "challenge"
+}
+
+# if locked out
+prop {
+    prop_name: "vendor.face.virtual.lockout"
+    type: Boolean
+    scope: Public
+    access: ReadWrite
+    api_name: "lockout"
+}
+
+# force all authenticate operations to fail
+prop {
+    prop_name: "vendor.face.virtual.operation_authenticate_fails"
+    type: Boolean
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_authenticate_fails"
+}
+
+# force all detectInteraction operations to fail
+prop {
+    prop_name: "vendor.face.virtual.operation_detect_interaction_fails"
+    type: Boolean
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_detect_interaction_fails"
+}
+
+# force all enroll operations to fail
+prop {
+    prop_name: "vendor.face.virtual.operation_enroll_fails"
+    type: Boolean
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_enroll_fails"
+}
+
+# add a latency to authentication operations
+# Note that this latency is the initial authentication latency that occurs before
+# the HAL will send AcquiredInfo::START and AcquiredInfo::FIRST_FRAME_RECEIVED
+prop {
+    prop_name: "vendor.face.virtual.operation_authenticate_latency"
+    type: Integer
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_authenticate_latency"
+}
+
+# add a latency to detectInteraction operations
+prop {
+    prop_name: "vendor.face.virtual.operation_detect_interaction_latency"
+    type: Integer
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_detect_interaction_latency"
+}
+
+# millisecond duration for authenticate operations
+# (waits for changes to enrollment_hit)
+prop {
+    prop_name: "vendor.face.virtual.operation_authenticate_duration"
+    type: Integer
+    scope: Public
+    access: ReadWrite
+    api_name: "operation_authenticate_duration"
+}
diff --git a/biometrics/face/aidl/default/tests/FakeFaceEngineTest.cpp b/biometrics/face/aidl/default/tests/FakeFaceEngineTest.cpp
new file mode 100644
index 0000000..c8ad6b7
--- /dev/null
+++ b/biometrics/face/aidl/default/tests/FakeFaceEngineTest.cpp
@@ -0,0 +1,383 @@
+/*
+ * 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 <android/binder_process.h>
+#include <face.sysprop.h>
+#include <gtest/gtest.h>
+
+#include <aidl/android/hardware/biometrics/face/BnSessionCallback.h>
+#include <android-base/logging.h>
+
+#include "FakeFaceEngine.h"
+
+using namespace ::android::face::virt;
+using namespace ::aidl::android::hardware::biometrics::face;
+using namespace ::aidl::android::hardware::keymaster;
+
+namespace aidl::android::hardware::biometrics::face {
+
+class TestSessionCallback : public BnSessionCallback {
+  public:
+    ndk::ScopedAStatus onChallengeGenerated(int64_t challenge) override {
+        mLastChallenge = challenge;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onChallengeRevoked(int64_t challenge) override {
+        mLastChallengeRevoked = challenge;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onError(Error error, int32_t) override {
+        mError = error;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onEnrollmentProgress(int32_t enrollmentId, int32_t remaining) override {
+        if (remaining == 0) mLastEnrolled = enrollmentId;
+        return ndk::ScopedAStatus::ok();
+    };
+
+    ::ndk::ScopedAStatus onAuthenticationSucceeded(int32_t enrollmentId,
+                                                   const HardwareAuthToken&) override {
+        mLastAuthenticated = enrollmentId;
+        mAuthenticateFailed = false;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onAuthenticationFailed() override {
+        mLastAuthenticated = 0;
+        mAuthenticateFailed = true;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onInteractionDetected() override {
+        mInteractionDetectedCount++;
+        return ndk::ScopedAStatus::ok();
+    };
+
+    ::ndk::ScopedAStatus onEnrollmentFrame(const EnrollmentFrame& frame) override {
+        mEnrollmentFrames.push_back(frame.data.vendorCode);
+        return ndk::ScopedAStatus::ok();
+    }
+
+    ::ndk::ScopedAStatus onEnrollmentsEnumerated(
+            const std::vector<int32_t>& enrollmentIds) override {
+        mLastEnrollmentsEnumerated = enrollmentIds;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onEnrollmentsRemoved(const std::vector<int32_t>& enrollmentIds) override {
+        mLastEnrollmentRemoved = enrollmentIds;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onAuthenticatorIdRetrieved(int64_t authenticatorId) override {
+        mLastAuthenticatorId = authenticatorId;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onAuthenticatorIdInvalidated(int64_t authenticatorId) override {
+        mLastAuthenticatorId = authenticatorId;
+        mAuthenticatorIdInvalidated = true;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onAuthenticationFrame(const AuthenticationFrame& /*authFrame*/) override {
+        return ndk::ScopedAStatus::ok();
+    }
+    ::ndk::ScopedAStatus onLockoutPermanent() override {
+        mLockoutPermanent = true;
+        return ndk::ScopedAStatus::ok();
+    };
+    ::ndk::ScopedAStatus onLockoutTimed(int64_t /* timeout */) override {
+        return ndk::ScopedAStatus::ok();
+    }
+    ::ndk::ScopedAStatus onLockoutCleared() override {
+        mLockoutPermanent = false;
+        return ndk::ScopedAStatus::ok();
+    }
+    ::ndk::ScopedAStatus onSessionClosed() override { return ndk::ScopedAStatus::ok(); }
+
+    ::ndk::ScopedAStatus onFeaturesRetrieved(const std::vector<Feature>& features) override {
+        mFeatures = features;
+        return ndk::ScopedAStatus::ok();
+    }
+
+    ::ndk::ScopedAStatus onFeatureSet(Feature feature) override {
+        mLastFeatureSet = feature;
+        return ndk::ScopedAStatus::ok();
+    }
+
+    Error mError = Error::UNKNOWN;
+    int64_t mLastChallenge = -1;
+    int64_t mLastChallengeRevoked = -1;
+    int32_t mLastEnrolled = -1;
+    int32_t mLastAuthenticated = -1;
+    int64_t mLastAuthenticatorId = -1;
+    std::vector<int32_t> mLastEnrollmentsEnumerated;
+    std::vector<int32_t> mLastEnrollmentRemoved;
+    std::vector<Feature> mFeatures;
+    Feature mLastFeatureSet;
+    std::vector<int32_t> mEnrollmentFrames;
+    bool mAuthenticateFailed = false;
+    bool mAuthenticatorIdInvalidated = false;
+    bool mLockoutPermanent = false;
+    int mInteractionDetectedCount = 0;
+};
+
+class FakeFaceEngineTest : public ::testing::Test {
+  protected:
+    void SetUp() override {
+        LOG(ERROR) << "JRM SETUP";
+        mCallback = ndk::SharedRefBase::make<TestSessionCallback>();
+        FaceHalProperties::enrollments({});
+        FaceHalProperties::challenge({});
+        FaceHalProperties::features({});
+        FaceHalProperties::authenticator_id({});
+        FaceHalProperties::strength("");
+    }
+
+    FakeFaceEngine mEngine;
+    std::shared_ptr<TestSessionCallback> mCallback;
+    std::promise<void> mCancel;
+};
+
+TEST_F(FakeFaceEngineTest, one_eq_one) {
+    ASSERT_EQ(1, 1);
+}
+
+TEST_F(FakeFaceEngineTest, GenerateChallenge) {
+    mEngine.generateChallengeImpl(mCallback.get());
+    ASSERT_EQ(FaceHalProperties::challenge().value(), mCallback->mLastChallenge);
+}
+
+TEST_F(FakeFaceEngineTest, RevokeChallenge) {
+    auto challenge = FaceHalProperties::challenge().value_or(10);
+    mEngine.revokeChallengeImpl(mCallback.get(), challenge);
+    ASSERT_FALSE(FaceHalProperties::challenge().has_value());
+    ASSERT_EQ(challenge, mCallback->mLastChallengeRevoked);
+}
+
+TEST_F(FakeFaceEngineTest, ResetLockout) {
+    FaceHalProperties::lockout(true);
+    mEngine.resetLockoutImpl(mCallback.get(), {});
+    ASSERT_FALSE(mCallback->mLockoutPermanent);
+    ASSERT_FALSE(FaceHalProperties::lockout().value_or(true));
+}
+
+TEST_F(FakeFaceEngineTest, AuthenticatorId) {
+    FaceHalProperties::authenticator_id(50);
+    mEngine.getAuthenticatorIdImpl(mCallback.get());
+    ASSERT_EQ(50, mCallback->mLastAuthenticatorId);
+    ASSERT_FALSE(mCallback->mAuthenticatorIdInvalidated);
+}
+
+TEST_F(FakeFaceEngineTest, GetAuthenticatorIdWeakReturnsZero) {
+    FaceHalProperties::strength("weak");
+    FaceHalProperties::authenticator_id(500);
+    mEngine.getAuthenticatorIdImpl(mCallback.get());
+    ASSERT_EQ(0, mCallback->mLastAuthenticatorId);
+    ASSERT_FALSE(mCallback->mAuthenticatorIdInvalidated);
+}
+
+TEST_F(FakeFaceEngineTest, AuthenticatorIdInvalidate) {
+    FaceHalProperties::authenticator_id(500);
+    mEngine.invalidateAuthenticatorIdImpl(mCallback.get());
+    ASSERT_NE(500, FaceHalProperties::authenticator_id().value());
+    ASSERT_TRUE(mCallback->mAuthenticatorIdInvalidated);
+}
+
+TEST_F(FakeFaceEngineTest, Enroll) {
+    FaceHalProperties::next_enrollment("1,0:30:true,1:0:true,2:0:true,3:0:true,4:0:true");
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.enrollImpl(mCallback.get(), hat, {} /*enrollmentType*/, {} /*features*/,
+                       mCancel.get_future());
+    ASSERT_FALSE(FaceHalProperties::next_enrollment().has_value());
+    ASSERT_EQ(1, FaceHalProperties::enrollments().size());
+    ASSERT_EQ(1, FaceHalProperties::enrollments()[0].value());
+    ASSERT_EQ(1, mCallback->mLastEnrolled);
+}
+
+TEST_F(FakeFaceEngineTest, EnrollFails) {
+    FaceHalProperties::next_enrollment("1,0:30:true,1:0:true,2:0:true,3:0:true,4:0:false");
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.enrollImpl(mCallback.get(), hat, {} /*enrollmentType*/, {} /*features*/,
+                       mCancel.get_future());
+    ASSERT_FALSE(FaceHalProperties::next_enrollment().has_value());
+    ASSERT_EQ(0, FaceHalProperties::enrollments().size());
+}
+
+TEST_F(FakeFaceEngineTest, EnrollCancel) {
+    FaceHalProperties::next_enrollment("1,0:30:true,1:0:true,2:0:true,3:0:true,4:0:false");
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mCancel.set_value();
+    mEngine.enrollImpl(mCallback.get(), hat, {} /*enrollmentType*/, {} /*features*/,
+                       mCancel.get_future());
+    ASSERT_EQ(Error::CANCELED, mCallback->mError);
+    ASSERT_EQ(-1, mCallback->mLastEnrolled);
+    ASSERT_EQ(0, FaceHalProperties::enrollments().size());
+    ASSERT_FALSE(FaceHalProperties::next_enrollment().has_value());
+}
+
+TEST_F(FakeFaceEngineTest, Authenticate) {
+    FaceHalProperties::enrollments({100});
+    FaceHalProperties::enrollment_hit(100);
+    mEngine.authenticateImpl(mCallback.get(), 0 /* operationId*/, mCancel.get_future());
+
+    ASSERT_EQ(100, mCallback->mLastAuthenticated);
+    ASSERT_FALSE(mCallback->mAuthenticateFailed);
+}
+
+TEST_F(FakeFaceEngineTest, AuthenticateCancel) {
+    FaceHalProperties::enrollments({100});
+    FaceHalProperties::enrollment_hit(100);
+    mCancel.set_value();
+    mEngine.authenticateImpl(mCallback.get(), 0 /* operationId*/, mCancel.get_future());
+    ASSERT_EQ(Error::CANCELED, mCallback->mError);
+}
+
+TEST_F(FakeFaceEngineTest, AuthenticateFailedForUnEnrolled) {
+    FaceHalProperties::enrollments({3});
+    FaceHalProperties::enrollment_hit(100);
+    mEngine.authenticateImpl(mCallback.get(), 0 /* operationId*/, mCancel.get_future());
+    ASSERT_EQ(Error::UNABLE_TO_PROCESS, mCallback->mError);
+    ASSERT_TRUE(mCallback->mAuthenticateFailed);
+}
+
+TEST_F(FakeFaceEngineTest, DetectInteraction) {
+    FaceHalProperties::enrollments({100});
+    FaceHalProperties::enrollment_hit(100);
+    ASSERT_EQ(0, mCallback->mInteractionDetectedCount);
+    mEngine.detectInteractionImpl(mCallback.get(), mCancel.get_future());
+    ASSERT_EQ(1, mCallback->mInteractionDetectedCount);
+}
+
+TEST_F(FakeFaceEngineTest, DetectInteractionCancel) {
+    FaceHalProperties::enrollments({100});
+    FaceHalProperties::enrollment_hit(100);
+    mCancel.set_value();
+    mEngine.detectInteractionImpl(mCallback.get(), mCancel.get_future());
+    ASSERT_EQ(Error::CANCELED, mCallback->mError);
+}
+
+TEST_F(FakeFaceEngineTest, GetFeatureEmpty) {
+    mEngine.getFeaturesImpl(mCallback.get());
+    ASSERT_TRUE(mCallback->mFeatures.empty());
+}
+
+TEST_F(FakeFaceEngineTest, SetFeature) {
+    FaceHalProperties::enrollments({1});
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, true);
+    auto features = mCallback->mFeatures;
+    ASSERT_TRUE(features.empty());
+    ASSERT_EQ(Feature::REQUIRE_ATTENTION, mCallback->mLastFeatureSet);
+
+    mEngine.getFeaturesImpl(mCallback.get());
+    features = mCallback->mFeatures;
+    ASSERT_FALSE(features.empty());
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_ATTENTION));
+}
+
+TEST_F(FakeFaceEngineTest, ToggleFeature) {
+    FaceHalProperties::enrollments({1});
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, true);
+    mEngine.getFeaturesImpl(mCallback.get());
+    auto features = mCallback->mFeatures;
+    ASSERT_FALSE(features.empty());
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_ATTENTION));
+
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, false);
+    mEngine.getFeaturesImpl(mCallback.get());
+    features = mCallback->mFeatures;
+    ASSERT_TRUE(features.empty());
+}
+
+TEST_F(FakeFaceEngineTest, TurningOffNonExistentFeatureDoesNothing) {
+    FaceHalProperties::enrollments({1});
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, false);
+    mEngine.getFeaturesImpl(mCallback.get());
+    auto features = mCallback->mFeatures;
+    ASSERT_TRUE(features.empty());
+}
+
+TEST_F(FakeFaceEngineTest, SetMultipleFeatures) {
+    FaceHalProperties::enrollments({1});
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, true);
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_DIVERSE_POSES, true);
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::DEBUG, true);
+    mEngine.getFeaturesImpl(mCallback.get());
+    auto features = mCallback->mFeatures;
+    ASSERT_EQ(3, features.size());
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_ATTENTION));
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_DIVERSE_POSES));
+    ASSERT_NE(features.end(), std::find(features.begin(), features.end(), Feature::DEBUG));
+}
+
+TEST_F(FakeFaceEngineTest, SetMultipleFeaturesAndTurnOffSome) {
+    FaceHalProperties::enrollments({1});
+    keymaster::HardwareAuthToken hat{.mac = {2, 4}};
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_ATTENTION, true);
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::REQUIRE_DIVERSE_POSES, true);
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::DEBUG, true);
+    mEngine.setFeatureImpl(mCallback.get(), hat, Feature::DEBUG, false);
+    mEngine.getFeaturesImpl(mCallback.get());
+    auto features = mCallback->mFeatures;
+    ASSERT_EQ(2, features.size());
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_ATTENTION));
+    ASSERT_NE(features.end(),
+              std::find(features.begin(), features.end(), Feature::REQUIRE_DIVERSE_POSES));
+    ASSERT_EQ(features.end(), std::find(features.begin(), features.end(), Feature::DEBUG));
+}
+
+TEST_F(FakeFaceEngineTest, Enumerate) {
+    FaceHalProperties::enrollments({120, 3});
+    mEngine.enumerateEnrollmentsImpl(mCallback.get());
+    auto enrolls = mCallback->mLastEnrollmentsEnumerated;
+    ASSERT_FALSE(enrolls.empty());
+    ASSERT_NE(enrolls.end(), std::find(enrolls.begin(), enrolls.end(), 120));
+    ASSERT_NE(enrolls.end(), std::find(enrolls.begin(), enrolls.end(), 3));
+}
+
+TEST_F(FakeFaceEngineTest, RemoveEnrollments) {
+    FaceHalProperties::enrollments({120, 3, 100});
+    mEngine.removeEnrollmentsImpl(mCallback.get(), {120, 100});
+    mEngine.enumerateEnrollmentsImpl(mCallback.get());
+    auto enrolls = mCallback->mLastEnrollmentsEnumerated;
+    ASSERT_FALSE(enrolls.empty());
+    ASSERT_EQ(enrolls.end(), std::find(enrolls.begin(), enrolls.end(), 120));
+    ASSERT_NE(enrolls.end(), std::find(enrolls.begin(), enrolls.end(), 3));
+    ASSERT_EQ(enrolls.end(), std::find(enrolls.begin(), enrolls.end(), 100));
+}
+
+TEST_F(FakeFaceEngineTest, ResetLockoutWithAuth) {
+    FaceHalProperties::lockout(true);
+    FaceHalProperties::enrollments({33});
+    FaceHalProperties::enrollment_hit(33);
+    auto cancelFuture = mCancel.get_future();
+    mEngine.authenticateImpl(mCallback.get(), 0 /* operationId*/, cancelFuture);
+
+    ASSERT_TRUE(mCallback->mLockoutPermanent);
+
+    mEngine.resetLockoutImpl(mCallback.get(), {} /* hat */);
+    ASSERT_FALSE(mCallback->mLockoutPermanent);
+    FaceHalProperties::enrollment_hit(33);
+    mEngine.authenticateImpl(mCallback.get(), 0 /* operationId*/, cancelFuture);
+    ASSERT_EQ(33, mCallback->mLastAuthenticated);
+    ASSERT_FALSE(mCallback->mAuthenticateFailed);
+}
+
+}  // namespace aidl::android::hardware::biometrics::face
\ No newline at end of file