Pass all input events to MetricsManager

The MetricsManager needs to receive UP/CANCEL events to trigger
atom reporting. I must have moved these lines around during the
refactor and overlooked this mistake.

This change also modifies MotionPredictor and MetricsManager to
hold a "ReportAtomFunction" to facilitate testing.

Test: `statsd_testdrive 718` shows atoms reported with `adb shell setenforce 0`.
Test: `atest frameworks/native/libs/input/tests/MotionPredictor_test.cpp -c` passes.
Test: `atest frameworks/native/libs/input/tests/MotionPredictorMetricsManager_test.cpp -c` passes.

Bug: 311066949

Change-Id: Icbb709bbb7cf548512e0d9aa062783d554b857e3

6 files changed, 151 insertions, 96 deletions

diff --git a/include/input/MotionPredictor.h b/include/input/MotionPredictor.h
index 8797962886..3b6e40183f 100644
--- a/include/input/MotionPredictor.h
+++ b/include/input/MotionPredictor.h
@@ -19,6 +19,7 @@
 #include <cstdint>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 #include <unordered_map>
 
@@ -57,20 +58,23 @@ static inline bool isMotionPredictionEnabled() {
  */
 class MotionPredictor {
 public:
+    using ReportAtomFunction = MotionPredictorMetricsManager::ReportAtomFunction;
+
     /**
      * Parameters:
      * predictionTimestampOffsetNanos: additional, constant shift to apply to the target
      * prediction time. The prediction will target the time t=(prediction time +
      * predictionTimestampOffsetNanos).
      *
-     * modelPath: filesystem path to a TfLiteMotionPredictorModel flatbuffer, or nullptr to use the
-     * default model path.
-     *
-     * checkEnableMotionPredition: the function to check whether the prediction should run. Used to
+     * checkEnableMotionPrediction: the function to check whether the prediction should run. Used to
      * provide an additional way of turning prediction on and off. Can be toggled at runtime.
+     *
+     * reportAtomFunction: the function that will be called to report prediction metrics. If
+     * omitted, the implementation will choose a default metrics reporting mechanism.
      */
     MotionPredictor(nsecs_t predictionTimestampOffsetNanos,
-                    std::function<bool()> checkEnableMotionPrediction = isMotionPredictionEnabled);
+                    std::function<bool()> checkEnableMotionPrediction = isMotionPredictionEnabled,
+                    ReportAtomFunction reportAtomFunction = {});
 
     /**
      * Record the actual motion received by the view. This event will be used for calculating the
@@ -95,6 +99,8 @@ private:
     std::optional<MotionEvent> mLastEvent;
 
     std::optional<MotionPredictorMetricsManager> mMetricsManager;
+
+    const ReportAtomFunction mReportAtomFunction;
 };
 
 } // namespace android
diff --git a/include/input/MotionPredictorMetricsManager.h b/include/input/MotionPredictorMetricsManager.h
index 12e50ba3b4..38472d8df7 100644
--- a/include/input/MotionPredictorMetricsManager.h
+++ b/include/input/MotionPredictorMetricsManager.h
@@ -18,7 +18,6 @@
 #include <cstdint>
 #include <functional>
 #include <limits>
-#include <optional>
 #include <vector>
 
 #include <input/Input.h> // for MotionEvent
@@ -37,15 +36,33 @@ namespace android {
  *
  * This class stores AggregatedStrokeMetrics, updating them as new MotionEvents are passed in. When
  * onRecord receives an UP or CANCEL event, this indicates the end of the stroke, and the final
- * AtomFields are computed and reported to the stats library.
+ * AtomFields are computed and reported to the stats library. The number of atoms reported is equal
+ * to the value of `maxNumPredictions` passed to the constructor. Each atom corresponds to one
+ * "prediction time bucket" — the amount of time into the future being predicted.
  *
  * If mMockLoggedAtomFields is set, the batch of AtomFields that are reported to the stats library
  * for one stroke are also stored in mMockLoggedAtomFields at the time they're reported.
  */
 class MotionPredictorMetricsManager {
 public:
-    // Note: the MetricsManager assumes that the input interval equals the prediction interval.
-    MotionPredictorMetricsManager(nsecs_t predictionInterval, size_t maxNumPredictions);
+    struct AtomFields;
+
+    using ReportAtomFunction = std::function<void(const AtomFields&)>;
+
+    static void defaultReportAtomFunction(const AtomFields& atomFields);
+
+    // Parameters:
+    //  • predictionInterval: the time interval between successive prediction target timestamps.
+    //    Note: the MetricsManager assumes that the input interval equals the prediction interval.
+    //  • maxNumPredictions: the maximum number of distinct target timestamps the prediction model
+    //    will generate predictions for. The MetricsManager reports this many atoms per stroke.
+    //  • [Optional] reportAtomFunction: the function that will be called to report metrics. If
+    //    omitted (or if an empty function is given), the `stats_write(…)` function from the Android
+    //    stats library will be used.
+    MotionPredictorMetricsManager(
+            nsecs_t predictionInterval,
+            size_t maxNumPredictions,
+            ReportAtomFunction reportAtomFunction = defaultReportAtomFunction);
 
     // This method should be called once for each call to MotionPredictor::record, receiving the
     // forwarded MotionEvent argument.
@@ -121,7 +138,7 @@ public:
     // magnitude makes it unobtainable in practice.)
     static const int NO_DATA_SENTINEL = std::numeric_limits<int32_t>::min();
 
-    // Final metrics reported in the atom.
+    // Final metric values reported in the atom.
     struct AtomFields {
         int deltaTimeBucketMilliseconds = 0;
 
@@ -140,15 +157,6 @@ public:
         int scaleInvariantOffTrajectoryRmse = NO_DATA_SENTINEL;   // millipixels
     };
 
-    // Allow tests to pass in a mock AtomFields pointer.
-    //
-    // When metrics are reported to the stats library on stroke end, they will also be written to
-    // mockLoggedAtomFields, overwriting existing data. The size of mockLoggedAtomFields will equal
-    // the number of calls to stats_write for that stroke.
-    void setMockLoggedAtomFields(std::vector<AtomFields>* mockLoggedAtomFields) {
-        mMockLoggedAtomFields = mockLoggedAtomFields;
-    }
-
 private:
     // The interval between consecutive predictions' target timestamps. We assume that the input
     // interval also equals this value.
@@ -172,11 +180,7 @@ private:
     std::vector<AggregatedStrokeMetrics> mAggregatedMetrics;
     std::vector<AtomFields> mAtomFields;
 
-    // Non-owning pointer to the location of mock AtomFields. If present, will be filled with the
-    // values reported to stats_write on each batch of reported metrics.
-    //
-    // This pointer must remain valid as long as the MotionPredictorMetricsManager exists.
-    std::vector<AtomFields>* mMockLoggedAtomFields = nullptr;
+    const ReportAtomFunction mReportAtomFunction;
 
     // Helper methods for the implementation of onRecord and onPredict.
 
@@ -196,10 +200,7 @@ private:
     // Computes the atom fields to mAtomFields from the values in mAggregatedMetrics.
     void computeAtomFields();
 
-    // Reports the metrics given by the current data in mAtomFields:
-    //  • If on an Android device, reports the metrics to stats_write.
-    //  • If mMockLoggedAtomFields is present, it will be overwritten with logged metrics, with one
-    //    AtomFields element per call to stats_write.
+    // Reports the current data in mAtomFields by calling mReportAtomFunction.
     void reportMetrics();
 };
 
diff --git a/libs/input/MotionPredictor.cpp b/libs/input/MotionPredictor.cpp
index 412931bc41..c4e3ff6dee 100644
--- a/libs/input/MotionPredictor.cpp
+++ b/libs/input/MotionPredictor.cpp
@@ -60,9 +60,11 @@ TfLiteMotionPredictorSample::Point convertPrediction(
 // --- MotionPredictor ---
 
 MotionPredictor::MotionPredictor(nsecs_t predictionTimestampOffsetNanos,
-                                 std::function<bool()> checkMotionPredictionEnabled)
+                                 std::function<bool()> checkMotionPredictionEnabled,
+                                 ReportAtomFunction reportAtomFunction)
       : mPredictionTimestampOffsetNanos(predictionTimestampOffsetNanos),
-        mCheckMotionPredictionEnabled(std::move(checkMotionPredictionEnabled)) {}
+        mCheckMotionPredictionEnabled(std::move(checkMotionPredictionEnabled)),
+        mReportAtomFunction(reportAtomFunction) {}
 
 android::base::Result<void> MotionPredictor::record(const MotionEvent& event) {
     if (mLastEvent && mLastEvent->getDeviceId() != event.getDeviceId()) {
@@ -90,6 +92,13 @@ android::base::Result<void> MotionPredictor::record(const MotionEvent& event) {
         mBuffers = std::make_unique<TfLiteMotionPredictorBuffers>(mModel->inputLength());
     }
 
+    // Pass input event to the MetricsManager.
+    if (!mMetricsManager) {
+        mMetricsManager.emplace(mModel->config().predictionInterval, mModel->outputLength(),
+                                mReportAtomFunction);
+    }
+    mMetricsManager->onRecord(event);
+
     const int32_t action = event.getActionMasked();
     if (action == AMOTION_EVENT_ACTION_UP || action == AMOTION_EVENT_ACTION_CANCEL) {
         ALOGD_IF(isDebug(), "End of event stream");
@@ -135,12 +144,6 @@ android::base::Result<void> MotionPredictor::record(const MotionEvent& event) {
     }
     mLastEvent->copyFrom(&event, /*keepHistory=*/false);
 
-    // Pass input event to the MetricsManager.
-    if (!mMetricsManager) {
-        mMetricsManager.emplace(mModel->config().predictionInterval, mModel->outputLength());
-    }
-    mMetricsManager->onRecord(event);
-
     return {};
 }
 
diff --git a/libs/input/MotionPredictorMetricsManager.cpp b/libs/input/MotionPredictorMetricsManager.cpp
index 67b103290f..0412d08181 100644
--- a/libs/input/MotionPredictorMetricsManager.cpp
+++ b/libs/input/MotionPredictorMetricsManager.cpp
@@ -46,13 +46,36 @@ inline constexpr float PATH_LENGTH_EPSILON = 0.001;
 
 } // namespace
 
-MotionPredictorMetricsManager::MotionPredictorMetricsManager(nsecs_t predictionInterval,
-                                                             size_t maxNumPredictions)
+void MotionPredictorMetricsManager::defaultReportAtomFunction(
+        const MotionPredictorMetricsManager::AtomFields& atomFields) {
+    // Call stats_write logging function only on Android targets (not supported on host).
+#ifdef __ANDROID__
+    android::stats::libinput::
+            stats_write(android::stats::libinput::STYLUS_PREDICTION_METRICS_REPORTED,
+                            /*stylus_vendor_id=*/0,
+                            /*stylus_product_id=*/0,
+                            atomFields.deltaTimeBucketMilliseconds,
+                            atomFields.alongTrajectoryErrorMeanMillipixels,
+                            atomFields.alongTrajectoryErrorStdMillipixels,
+                            atomFields.offTrajectoryRmseMillipixels,
+                            atomFields.pressureRmseMilliunits,
+                            atomFields.highVelocityAlongTrajectoryRmse,
+                            atomFields.highVelocityOffTrajectoryRmse,
+                            atomFields.scaleInvariantAlongTrajectoryRmse,
+                            atomFields.scaleInvariantOffTrajectoryRmse);
+#endif
+}
+
+MotionPredictorMetricsManager::MotionPredictorMetricsManager(
+        nsecs_t predictionInterval,
+        size_t maxNumPredictions,
+        ReportAtomFunction reportAtomFunction)
       : mPredictionInterval(predictionInterval),
         mMaxNumPredictions(maxNumPredictions),
         mRecentGroundTruthPoints(maxNumPredictions + 1),
         mAggregatedMetrics(maxNumPredictions),
-        mAtomFields(maxNumPredictions) {}
+        mAtomFields(maxNumPredictions),
+        mReportAtomFunction(reportAtomFunction ? reportAtomFunction : defaultReportAtomFunction) {}
 
 void MotionPredictorMetricsManager::onRecord(const MotionEvent& inputEvent) {
     // Convert MotionEvent to GroundTruthPoint.
@@ -81,8 +104,8 @@ void MotionPredictorMetricsManager::onRecord(const MotionEvent& inputEvent) {
             if (mRecentGroundTruthPoints.size() >= 2) {
                 computeAtomFields();
                 reportMetrics();
-                break;
             }
+            break;
         }
     }
 }
@@ -345,28 +368,10 @@ void MotionPredictorMetricsManager::computeAtomFields() {
 }
 
 void MotionPredictorMetricsManager::reportMetrics() {
-    // Report one atom for each time bucket.
+    LOG_ALWAYS_FATAL_IF(!mReportAtomFunction);
+    // Report one atom for each prediction time bucket.
     for (size_t i = 0; i < mAtomFields.size(); ++i) {
-        // Call stats_write logging function only on Android targets (not supported on host).
-#ifdef __ANDROID__
-        android::stats::libinput::
-                stats_write(android::stats::libinput::STYLUS_PREDICTION_METRICS_REPORTED,
-                            /*stylus_vendor_id=*/0,
-                            /*stylus_product_id=*/0, mAtomFields[i].deltaTimeBucketMilliseconds,
-                            mAtomFields[i].alongTrajectoryErrorMeanMillipixels,
-                            mAtomFields[i].alongTrajectoryErrorStdMillipixels,
-                            mAtomFields[i].offTrajectoryRmseMillipixels,
-                            mAtomFields[i].pressureRmseMilliunits,
-                            mAtomFields[i].highVelocityAlongTrajectoryRmse,
-                            mAtomFields[i].highVelocityOffTrajectoryRmse,
-                            mAtomFields[i].scaleInvariantAlongTrajectoryRmse,
-                            mAtomFields[i].scaleInvariantOffTrajectoryRmse);
-#endif
-    }
-
-    // Set mock atom fields, if available.
-    if (mMockLoggedAtomFields != nullptr) {
-        *mMockLoggedAtomFields = mAtomFields;
+        mReportAtomFunction(mAtomFields[i]);
     }
 }
 
diff --git a/libs/input/tests/MotionPredictorMetricsManager_test.cpp b/libs/input/tests/MotionPredictorMetricsManager_test.cpp
index b420a5a4e7..31cc1459fc 100644
--- a/libs/input/tests/MotionPredictorMetricsManager_test.cpp
+++ b/libs/input/tests/MotionPredictorMetricsManager_test.cpp
@@ -39,6 +39,7 @@ using ::testing::Matches;
 using GroundTruthPoint = MotionPredictorMetricsManager::GroundTruthPoint;
 using PredictionPoint = MotionPredictorMetricsManager::PredictionPoint;
 using AtomFields = MotionPredictorMetricsManager::AtomFields;
+using ReportAtomFunction = MotionPredictorMetricsManager::ReportAtomFunction;
 
 inline constexpr int NANOS_PER_MILLIS = 1'000'000;
 
@@ -664,9 +665,16 @@ TEST(ErrorComputationHelperTest, ComputePressureRmsesSimpleTest) {
 
 // --- MotionPredictorMetricsManager tests. ---
 
-// Helper function that instantiates a MetricsManager with the given mock logged AtomFields. Takes
-// vectors of ground truth and prediction points of the same length, and passes these points to the
-// MetricsManager. The format of these vectors is expected to be:
+// Creates a mock atom reporting function that appends the reported atom to the given vector.
+ReportAtomFunction createMockReportAtomFunction(std::vector<AtomFields>& reportedAtomFields) {
+    return [&reportedAtomFields](const AtomFields& atomFields) -> void {
+        reportedAtomFields.push_back(atomFields);
+    };
+}
+
+// Helper function that instantiates a MetricsManager that reports metrics to outReportedAtomFields.
+// Takes vectors of ground truth and prediction points of the same length, and passes these points
+// to the MetricsManager. The format of these vectors is expected to be:
 //  • groundTruthPoints: chronologically-ordered ground truth points, with at least 2 elements.
 //  • predictionPoints: the first index points to a vector of predictions corresponding to the
 //    source ground truth point with the same index.
@@ -678,15 +686,16 @@ TEST(ErrorComputationHelperTest, ComputePressureRmsesSimpleTest) {
 //       prediction sets (that is, excluding the first and last). Thus, groundTruthPoints and
 //       predictionPoints should have size at least TEST_MAX_NUM_PREDICTIONS + 2.
 //
-// The passed-in outAtomFields will contain the logged AtomFields when the function returns.
+// When the function returns, outReportedAtomFields will contain the reported AtomFields.
 //
 // This function returns void so that it can use test assertions.
 void runMetricsManager(const std::vector<GroundTruthPoint>& groundTruthPoints,
                        const std::vector<std::vector<PredictionPoint>>& predictionPoints,
-                       std::vector<AtomFields>& outAtomFields) {
+                       std::vector<AtomFields>& outReportedAtomFields) {
     MotionPredictorMetricsManager metricsManager(TEST_PREDICTION_INTERVAL_NANOS,
-                                                 TEST_MAX_NUM_PREDICTIONS);
-    metricsManager.setMockLoggedAtomFields(&outAtomFields);
+                                                 TEST_MAX_NUM_PREDICTIONS,
+                                                 createMockReportAtomFunction(
+                                                         outReportedAtomFields));
 
     // Validate structure of groundTruthPoints and predictionPoints.
     ASSERT_EQ(predictionPoints.size(), groundTruthPoints.size());
@@ -712,18 +721,18 @@ void runMetricsManager(const std::vector<GroundTruthPoint>& groundTruthPoints,
 //  • Input: no prediction data.
 //  • Expectation: no metrics should be logged.
 TEST(MotionPredictorMetricsManagerTest, NoPredictions) {
-    std::vector<AtomFields> mockLoggedAtomFields;
+    std::vector<AtomFields> reportedAtomFields;
     MotionPredictorMetricsManager metricsManager(TEST_PREDICTION_INTERVAL_NANOS,
-                                                 TEST_MAX_NUM_PREDICTIONS);
-    metricsManager.setMockLoggedAtomFields(&mockLoggedAtomFields);
+                                                 TEST_MAX_NUM_PREDICTIONS,
+                                                 createMockReportAtomFunction(reportedAtomFields));
 
     metricsManager.onRecord(makeMotionEvent(
             GroundTruthPoint{{.position = Eigen::Vector2f(0, 0), .pressure = 0}, .timestamp = 0}));
     metricsManager.onRecord(makeLiftMotionEvent());
 
-    // Check that mockLoggedAtomFields is still empty (as it was initialized empty), ensuring that
+    // Check that reportedAtomFields is still empty (as it was initialized empty), ensuring that
     // no metrics were logged.
-    EXPECT_EQ(0u, mockLoggedAtomFields.size());
+    EXPECT_EQ(0u, reportedAtomFields.size());
 }
 
 // Perfect predictions test:
@@ -744,14 +753,14 @@ TEST(MotionPredictorMetricsManagerTest, ConstantGroundTruthPerfectPredictions) {
         groundTruthPoint.timestamp += TEST_PREDICTION_INTERVAL_NANOS;
     }
 
-    std::vector<AtomFields> atomFields;
-    runMetricsManager(groundTruthPoints, predictionPoints, atomFields);
+    std::vector<AtomFields> reportedAtomFields;
+    runMetricsManager(groundTruthPoints, predictionPoints, reportedAtomFields);
 
-    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, atomFields.size());
+    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, reportedAtomFields.size());
     // Check that errors are all zero, or NO_DATA_SENTINEL for unreported metrics.
-    for (size_t i = 0; i < atomFields.size(); ++i) {
+    for (size_t i = 0; i < reportedAtomFields.size(); ++i) {
         SCOPED_TRACE(testing::Message() << "i = " << i);
-        const AtomFields& atom = atomFields[i];
+        const AtomFields& atom = reportedAtomFields[i];
         const nsecs_t deltaTimeBucketNanos = TEST_PREDICTION_INTERVAL_NANOS * (i + 1);
         EXPECT_EQ(deltaTimeBucketNanos / NANOS_PER_MILLIS, atom.deltaTimeBucketMilliseconds);
         // General errors: reported for every time bucket.
@@ -764,7 +773,7 @@ TEST(MotionPredictorMetricsManagerTest, ConstantGroundTruthPerfectPredictions) {
         EXPECT_EQ(NO_DATA_SENTINEL, atom.highVelocityAlongTrajectoryRmse);
         EXPECT_EQ(NO_DATA_SENTINEL, atom.highVelocityOffTrajectoryRmse);
         // Scale-invariant errors: reported only for the last time bucket.
-        if (i + 1 == atomFields.size()) {
+        if (i + 1 == reportedAtomFields.size()) {
             EXPECT_EQ(0, atom.scaleInvariantAlongTrajectoryRmse);
             EXPECT_EQ(0, atom.scaleInvariantOffTrajectoryRmse);
         } else {
@@ -801,14 +810,14 @@ TEST(MotionPredictorMetricsManagerTest, QuadraticPressureLinearPredictions) {
             computePressureRmses(groundTruthPoints, predictionPoints);
 
     // Run test.
-    std::vector<AtomFields> atomFields;
-    runMetricsManager(groundTruthPoints, predictionPoints, atomFields);
+    std::vector<AtomFields> reportedAtomFields;
+    runMetricsManager(groundTruthPoints, predictionPoints, reportedAtomFields);
 
     // Check logged metrics match expectations.
-    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, atomFields.size());
-    for (size_t i = 0; i < atomFields.size(); ++i) {
+    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, reportedAtomFields.size());
+    for (size_t i = 0; i < reportedAtomFields.size(); ++i) {
         SCOPED_TRACE(testing::Message() << "i = " << i);
-        const AtomFields& atom = atomFields[i];
+        const AtomFields& atom = reportedAtomFields[i];
         // Check time bucket delta matches expectation based on index and prediction interval.
         const nsecs_t deltaTimeBucketNanos = TEST_PREDICTION_INTERVAL_NANOS * (i + 1);
         EXPECT_EQ(deltaTimeBucketNanos / NANOS_PER_MILLIS, atom.deltaTimeBucketMilliseconds);
@@ -845,14 +854,14 @@ TEST(MotionPredictorMetricsManagerTest, QuadraticPositionLinearPredictionsGenera
             computeGeneralPositionErrors(groundTruthPoints, predictionPoints);
 
     // Run test.
-    std::vector<AtomFields> atomFields;
-    runMetricsManager(groundTruthPoints, predictionPoints, atomFields);
+    std::vector<AtomFields> reportedAtomFields;
+    runMetricsManager(groundTruthPoints, predictionPoints, reportedAtomFields);
 
     // Check logged metrics match expectations.
-    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, atomFields.size());
-    for (size_t i = 0; i < atomFields.size(); ++i) {
+    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, reportedAtomFields.size());
+    for (size_t i = 0; i < reportedAtomFields.size(); ++i) {
         SCOPED_TRACE(testing::Message() << "i = " << i);
-        const AtomFields& atom = atomFields[i];
+        const AtomFields& atom = reportedAtomFields[i];
         // Check time bucket delta matches expectation based on index and prediction interval.
         const nsecs_t deltaTimeBucketNanos = TEST_PREDICTION_INTERVAL_NANOS * (i + 1);
         EXPECT_EQ(deltaTimeBucketNanos / NANOS_PER_MILLIS, atom.deltaTimeBucketMilliseconds);
@@ -896,14 +905,14 @@ TEST(MotionPredictorMetricsManagerTest, CounterclockwiseOctagonGroundTruthLinear
             computeGeneralPositionErrors(groundTruthPoints, predictionPoints);
 
     // Run test.
-    std::vector<AtomFields> atomFields;
-    runMetricsManager(groundTruthPoints, predictionPoints, atomFields);
+    std::vector<AtomFields> reportedAtomFields;
+    runMetricsManager(groundTruthPoints, predictionPoints, reportedAtomFields);
 
     // Check logged metrics match expectations.
-    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, atomFields.size());
-    for (size_t i = 0; i < atomFields.size(); ++i) {
+    ASSERT_EQ(TEST_MAX_NUM_PREDICTIONS, reportedAtomFields.size());
+    for (size_t i = 0; i < reportedAtomFields.size(); ++i) {
         SCOPED_TRACE(testing::Message() << "i = " << i);
-        const AtomFields& atom = atomFields[i];
+        const AtomFields& atom = reportedAtomFields[i];
         const nsecs_t deltaTimeBucketNanos = TEST_PREDICTION_INTERVAL_NANOS * (i + 1);
         EXPECT_EQ(deltaTimeBucketNanos / NANOS_PER_MILLIS, atom.deltaTimeBucketMilliseconds);
 
@@ -926,7 +935,7 @@ TEST(MotionPredictorMetricsManagerTest, CounterclockwiseOctagonGroundTruthLinear
         // to general errors (where reported).
         //
         // As above, use absolute value for RMSE, since it must be non-negative.
-        if (i + 2 >= atomFields.size()) {
+        if (i + 2 >= reportedAtomFields.size()) {
             EXPECT_NEAR(static_cast<int>(
                                 1000 * std::abs(generalPositionErrors[i].alongTrajectoryErrorMean)),
                         atom.highVelocityAlongTrajectoryRmse, 1);
@@ -946,7 +955,7 @@ TEST(MotionPredictorMetricsManagerTest, CounterclockwiseOctagonGroundTruthLinear
         // to scale-invariant errors by dividing by `strokeVelocty * TEST_MAX_NUM_PREDICTIONS`.
         //
         // As above, use absolute value for RMSE, since it must be non-negative.
-        if (i + 1 == atomFields.size()) {
+        if (i + 1 == reportedAtomFields.size()) {
             const float pathLength = strokeVelocity * TEST_MAX_NUM_PREDICTIONS;
             std::vector<float> alongTrajectoryAbsoluteErrors;
             std::vector<float> offTrajectoryAbsoluteErrors;
diff --git a/libs/input/tests/MotionPredictor_test.cpp b/libs/input/tests/MotionPredictor_test.cpp
index 4ac7ae920e..33431146ea 100644
--- a/libs/input/tests/MotionPredictor_test.cpp
+++ b/libs/input/tests/MotionPredictor_test.cpp
@@ -147,4 +147,35 @@ TEST(MotionPredictorTest, FlagDisablesPrediction) {
     ASSERT_FALSE(predictor.isPredictionAvailable(/*deviceId=*/1, AINPUT_SOURCE_TOUCHSCREEN));
 }
 
+using AtomFields = MotionPredictorMetricsManager::AtomFields;
+using ReportAtomFunction = MotionPredictorMetricsManager::ReportAtomFunction;
+
+// Creates a mock atom reporting function that appends the reported atom to the given vector.
+// The passed-in pointer must not be nullptr.
+ReportAtomFunction createMockReportAtomFunction(std::vector<AtomFields>* reportedAtomFields) {
+    return [reportedAtomFields](const AtomFields& atomFields) -> void {
+        reportedAtomFields->push_back(atomFields);
+    };
+}
+
+TEST(MotionPredictorMetricsManagerIntegrationTest, ReportsMetrics) {
+    std::vector<AtomFields> reportedAtomFields;
+    MotionPredictor predictor(/*predictionTimestampOffsetNanos=*/0,
+                              []() { return true /*enable prediction*/; },
+                              createMockReportAtomFunction(&reportedAtomFields));
+
+    ASSERT_TRUE(predictor.record(getMotionEvent(DOWN, 1, 1, 0ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(MOVE, 2, 2, 4ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(MOVE, 3, 3, 8ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(MOVE, 4, 4, 12ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(MOVE, 5, 5, 16ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(MOVE, 6, 6, 20ms, /*deviceId=*/0)).ok());
+    ASSERT_TRUE(predictor.record(getMotionEvent(UP, 7, 7, 24ms, /*deviceId=*/0)).ok());
+
+    // The number of atoms reported should equal the number of prediction time buckets, which is
+    // given by the prediction model's output length. For now, this value is always 5, and we
+    // hardcode it because it's not publicly accessible from the MotionPredictor.
+    EXPECT_EQ(5u, reportedAtomFields.size());
+}
+
 } // namespace android