diff --git a/keystore2/watchdog/src/lib.rs b/keystore2/watchdog/src/lib.rs
index baed5ca..ff05783 100644
--- a/keystore2/watchdog/src/lib.rs
+++ b/keystore2/watchdog/src/lib.rs
@@ -29,6 +29,9 @@
     time::{Duration, Instant},
 };
 
+#[cfg(test)]
+mod tests;
+
 /// Represents a Watchdog record. It can be created with `Watchdog::watch` or
 /// `Watchdog::watch_with`. It disarms the record when dropped.
 pub struct WatchPoint {
@@ -332,86 +335,3 @@
         state.state = State::Running;
     }
 }
-
-#[cfg(test)]
-mod tests {
-
-    use super::*;
-    use std::sync::atomic;
-    use std::thread;
-    use std::time::Duration;
-
-    /// Count the number of times `Debug::fmt` is invoked.
-    #[derive(Default, Clone)]
-    struct DebugCounter(Arc<atomic::AtomicU8>);
-    impl DebugCounter {
-        fn value(&self) -> u8 {
-            self.0.load(atomic::Ordering::Relaxed)
-        }
-    }
-    impl std::fmt::Debug for DebugCounter {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
-            let count = self.0.fetch_add(1, atomic::Ordering::Relaxed);
-            write!(f, "hit_count: {count}")
-        }
-    }
-
-    #[test]
-    fn test_watchdog() {
-        android_logger::init_once(
-            android_logger::Config::default()
-                .with_tag("keystore2_watchdog_tests")
-                .with_max_level(log::LevelFilter::Debug),
-        );
-
-        let wd = Watchdog::new(Duration::from_secs(3));
-        let hit_counter = DebugCounter::default();
-        let wp = Watchdog::watch_with(
-            &wd,
-            "test_watchdog",
-            Duration::from_millis(100),
-            hit_counter.clone(),
-        );
-        assert_eq!(0, hit_counter.value());
-        thread::sleep(Duration::from_millis(500));
-        assert_eq!(1, hit_counter.value());
-        thread::sleep(Duration::from_secs(1));
-        assert_eq!(1, hit_counter.value());
-
-        drop(wp);
-        thread::sleep(Duration::from_secs(10));
-        assert_eq!(1, hit_counter.value());
-        let (_, ref state) = *wd.state;
-        let state = state.lock().unwrap();
-        assert_eq!(state.state, State::NotRunning);
-    }
-
-    #[test]
-    fn test_watchdog_backoff() {
-        android_logger::init_once(
-            android_logger::Config::default()
-                .with_tag("keystore2_watchdog_tests")
-                .with_max_level(log::LevelFilter::Debug),
-        );
-
-        let wd = Watchdog::new(Duration::from_secs(3));
-        let hit_counter = DebugCounter::default();
-        let wp = Watchdog::watch_with(
-            &wd,
-            "test_watchdog",
-            Duration::from_millis(100),
-            hit_counter.clone(),
-        );
-        assert_eq!(0, hit_counter.value());
-        thread::sleep(Duration::from_millis(500));
-        assert_eq!(1, hit_counter.value());
-        thread::sleep(Duration::from_secs(6));
-        assert_eq!(2, hit_counter.value());
-        thread::sleep(Duration::from_secs(11));
-        assert_eq!(3, hit_counter.value());
-
-        drop(wp);
-        thread::sleep(Duration::from_secs(4));
-        assert_eq!(3, hit_counter.value());
-    }
-}
diff --git a/keystore2/watchdog/src/tests.rs b/keystore2/watchdog/src/tests.rs
new file mode 100644
index 0000000..d35c0dd
--- /dev/null
+++ b/keystore2/watchdog/src/tests.rs
@@ -0,0 +1,86 @@
+// Copyright 2021, 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.
+
+//! Watchdog tests.
+
+use super::*;
+use std::sync::atomic;
+use std::thread;
+use std::time::Duration;
+
+/// Count the number of times `Debug::fmt` is invoked.
+#[derive(Default, Clone)]
+struct DebugCounter(Arc<atomic::AtomicU8>);
+impl DebugCounter {
+    fn value(&self) -> u8 {
+        self.0.load(atomic::Ordering::Relaxed)
+    }
+}
+impl std::fmt::Debug for DebugCounter {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
+        let count = self.0.fetch_add(1, atomic::Ordering::Relaxed);
+        write!(f, "hit_count: {count}")
+    }
+}
+
+#[test]
+fn test_watchdog() {
+    android_logger::init_once(
+        android_logger::Config::default()
+            .with_tag("keystore2_watchdog_tests")
+            .with_max_level(log::LevelFilter::Debug),
+    );
+
+    let wd = Watchdog::new(Duration::from_secs(3));
+    let hit_counter = DebugCounter::default();
+    let wp =
+        Watchdog::watch_with(&wd, "test_watchdog", Duration::from_millis(100), hit_counter.clone());
+    assert_eq!(0, hit_counter.value());
+    thread::sleep(Duration::from_millis(500));
+    assert_eq!(1, hit_counter.value());
+    thread::sleep(Duration::from_secs(1));
+    assert_eq!(1, hit_counter.value());
+
+    drop(wp);
+    thread::sleep(Duration::from_secs(10));
+    assert_eq!(1, hit_counter.value());
+    let (_, ref state) = *wd.state;
+    let state = state.lock().unwrap();
+    assert_eq!(state.state, State::NotRunning);
+}
+
+#[test]
+fn test_watchdog_backoff() {
+    android_logger::init_once(
+        android_logger::Config::default()
+            .with_tag("keystore2_watchdog_tests")
+            .with_max_level(log::LevelFilter::Debug),
+    );
+
+    let wd = Watchdog::new(Duration::from_secs(3));
+    let hit_counter = DebugCounter::default();
+    let wp =
+        Watchdog::watch_with(&wd, "test_watchdog", Duration::from_millis(100), hit_counter.clone());
+    assert_eq!(0, hit_counter.value());
+    thread::sleep(Duration::from_millis(500));
+    assert_eq!(1, hit_counter.value());
+    thread::sleep(Duration::from_secs(6));
+    assert_eq!(2, hit_counter.value());
+    thread::sleep(Duration::from_secs(11));
+    assert_eq!(3, hit_counter.value());
+
+    drop(wp);
+    thread::sleep(Duration::from_secs(4));
+    assert_eq!(3, hit_counter.value());
+}