diff --git a/y2020/control_loops/drivetrain/BUILD b/y2020/control_loops/drivetrain/BUILD
index 41c6d81..de669d6 100644
--- a/y2020/control_loops/drivetrain/BUILD
+++ b/y2020/control_loops/drivetrain/BUILD
@@ -125,6 +125,27 @@
     ],
 )
 
+cc_test(
+    name = "drivetrain_replay_test",
+    srcs = ["drivetrain_replay_test.cc"],
+    data = [
+        "//y2020:config.json",
+        "@drivetrain_replay//file:spinning_wheels_while_still.bfbs",
+    ],
+    deps = [
+        ":drivetrain_base",
+        "//aos:configuration",
+        "//aos:init",
+        "//aos/events:shm_event_loop",
+        "//aos/events:simulated_event_loop",
+        "//aos/events/logging:logger",
+        "//aos/testing:googletest",
+        "//frc971/control_loops/drivetrain:drivetrain_lib",
+        "@com_github_gflags_gflags//:gflags",
+        "@com_github_google_glog//:glog",
+    ],
+)
+
 cc_binary(
     name = "drivetrain_replay",
     srcs = ["drivetrain_replay.cc"],
diff --git a/y2020/control_loops/drivetrain/drivetrain_replay_test.cc b/y2020/control_loops/drivetrain/drivetrain_replay_test.cc
new file mode 100644
index 0000000..6933a51
--- /dev/null
+++ b/y2020/control_loops/drivetrain/drivetrain_replay_test.cc
@@ -0,0 +1,99 @@
+// This file serves to test replaying the localizer over existing logfiles to
+// check for regressions. Currently, it just uses a single logfile pulled from
+// running the 2016 robot against a wall and confirming that the X/Y estimate
+// does not change too much.
+//
+// Note that the current logfile test will break once we update the drivetrain
+// config for 2020, since both the gear ratios and IMU transformation wil no
+// longer be valid.
+// TODO(james): Do something about that when the time comes--could just copy
+// the existing drivetrain config into this file and use it directly.
+#include "gtest/gtest.h"
+
+#include "aos/configuration.h"
+#include "aos/events/logging/logger.h"
+#include "aos/events/simulated_event_loop.h"
+#include "aos/init.h"
+#include "aos/json_to_flatbuffer.h"
+#include "aos/network/team_number.h"
+#include "frc971/control_loops/drivetrain/drivetrain.h"
+#include "gflags/gflags.h"
+#include "y2020/control_loops/drivetrain/drivetrain_base.h"
+
+DEFINE_string(
+    logfile, "external/drivetrain_replay/file/spinning_wheels_while_still.bfbs",
+    "Name of the logfile to read from.");
+DEFINE_string(config, "y2020/config.json",
+              "Name of the config file to replay using.");
+
+namespace y2020 {
+namespace control_loops {
+namespace drivetrain {
+namespace testing {
+
+class DrivetrainReplayTest : public ::testing::Test {
+ public:
+  DrivetrainReplayTest()
+      : config_(aos::configuration::ReadConfig(FLAGS_config)),
+        reader_(FLAGS_logfile, &config_.message()) {
+    aos::network::OverrideTeamNumber(971);
+
+    // TODO(james): Actually enforce not sending on the same buses as the
+    // logfile spews out.
+    reader_.RemapLoggedChannel("/drivetrain",
+                              "frc971.control_loops.drivetrain.Status");
+    reader_.RemapLoggedChannel("/drivetrain",
+                              "frc971.control_loops.drivetrain.Output");
+    reader_.Register();
+
+    drivetrain_event_loop_ =
+        reader_.event_loop_factory()->MakeEventLoop("drivetrain");
+    drivetrain_event_loop_->SkipTimingReport();
+
+    localizer_ =
+        std::make_unique<frc971::control_loops::drivetrain::DeadReckonEkf>(
+            drivetrain_event_loop_.get(), GetDrivetrainConfig());
+    drivetrain_ =
+        std::make_unique<frc971::control_loops::drivetrain::DrivetrainLoop>(
+            GetDrivetrainConfig(), drivetrain_event_loop_.get(),
+            localizer_.get());
+
+    test_event_loop_ =
+        reader_.event_loop_factory()->MakeEventLoop("drivetrain");
+    status_fetcher_ = test_event_loop_->MakeFetcher<
+        frc971::control_loops::drivetrain::Status>("/drivetrain");
+  }
+
+  const aos::FlatbufferDetachedBuffer<aos::Configuration> config_;
+  aos::logger::LogReader reader_;
+
+  std::unique_ptr<aos::EventLoop> drivetrain_event_loop_;
+  std::unique_ptr<frc971::control_loops::drivetrain::DeadReckonEkf> localizer_;
+  std::unique_ptr<frc971::control_loops::drivetrain::DrivetrainLoop>
+      drivetrain_;
+  std::unique_ptr<aos::EventLoop> test_event_loop_;
+
+  aos::Fetcher<frc971::control_loops::drivetrain::Status> status_fetcher_;
+};
+
+// Tests that we do a good job of trusting the IMU when the wheels are spinning
+// and the actual robot is not moving.
+TEST_F(DrivetrainReplayTest, SpinningWheels) {
+  reader_.event_loop_factory()->Run();
+
+  ASSERT_TRUE(status_fetcher_.Fetch());
+  ASSERT_TRUE(status_fetcher_->has_x());
+  ASSERT_TRUE(status_fetcher_->has_y());
+  ASSERT_TRUE(status_fetcher_->has_theta());
+  EXPECT_LT(std::abs(status_fetcher_->x()), 0.1);
+  // Because the encoders should not be affecting the y or yaw axes, expect a
+  // reasonably precise result (although, since this is a real worl dtest, the
+  // robot probably did actually move be some non-zero amount).
+  EXPECT_LT(std::abs(status_fetcher_->y()), 0.05);
+  EXPECT_LT(std::abs(status_fetcher_->theta()), 0.02);
+}
+
+}  // namespace testing
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2020