diff --git a/tests/lib/Android.bp b/tests/lib/Android.bp
new file mode 100644
index 0000000..f45a81c
--- /dev/null
+++ b/tests/lib/Android.bp
@@ -0,0 +1,26 @@
+//
+// Copyright (C) 2019 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.
+//
+
+java_library {
+    name: "net-tests-utils",
+    srcs: [
+        "src/**/*.java",
+        "src/**/*.kt",
+    ],
+    static_libs: [
+        "kotlin-test",
+    ],
+}
diff --git a/tests/lib/src/com/android/testutils/HandlerUtils.kt b/tests/lib/src/com/android/testutils/HandlerUtils.kt
new file mode 100644
index 0000000..3dce5a5
--- /dev/null
+++ b/tests/lib/src/com/android/testutils/HandlerUtils.kt
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+package com.android.testutils
+
+import android.os.ConditionVariable
+import android.os.Handler
+import android.os.HandlerThread
+import java.util.concurrent.Executor
+import kotlin.test.fail
+
+/**
+ * Block until the specified Handler or HandlerThread becomes idle, or until timeoutMs has passed.
+ */
+fun Handler.waitForIdle(timeoutMs: Long) = waitForIdleHandler(this, timeoutMs)
+fun HandlerThread.waitForIdle(timeoutMs: Long) = waitForIdleHandler(this.threadHandler, timeoutMs)
+fun waitForIdleHandler(handler: HandlerThread, timeoutMs: Long) {
+    waitForIdleHandler(handler.threadHandler, timeoutMs)
+}
+fun waitForIdleHandler(handler: Handler, timeoutMs: Long) {
+    val cv = ConditionVariable(false)
+    handler.post(cv::open)
+    if (!cv.block(timeoutMs)) {
+        fail("Handler did not become idle after ${timeoutMs}ms")
+    }
+}
+
+/**
+ * Block until the given Serial Executor becomes idle, or until timeoutMs has passed.
+ */
+fun waitForIdleSerialExecutor(executor: Executor, timeoutMs: Long) {
+    val cv = ConditionVariable()
+    executor.execute(cv::open)
+    if (!cv.block(timeoutMs)) {
+        fail("Executor did not become idle after ${timeoutMs}ms")
+    }
+}
diff --git a/tests/unit/Android.bp b/tests/unit/Android.bp
index 85951eb..48b13b0 100644
--- a/tests/unit/Android.bp
+++ b/tests/unit/Android.bp
@@ -23,6 +23,7 @@
     static_libs: [
         "androidx.test.rules",
         "mockito-target-extended-minus-junit4",
+        "net-tests-utils",
         "NetworkStackBase",
         "testables",
     ],
diff --git a/tests/unit/src/com/android/server/connectivity/NetworkMonitorTest.java b/tests/unit/src/com/android/server/connectivity/NetworkMonitorTest.java
index 262641d..e4c1d17 100644
--- a/tests/unit/src/com/android/server/connectivity/NetworkMonitorTest.java
+++ b/tests/unit/src/com/android/server/connectivity/NetworkMonitorTest.java
@@ -92,6 +92,7 @@
 import com.android.networkstack.R;
 import com.android.networkstack.metrics.DataStallDetectionStats;
 import com.android.networkstack.metrics.DataStallStatsUtils;
+import com.android.testutils.HandlerUtilsKt;
 
 import org.junit.After;
 import org.junit.Before;
@@ -420,7 +421,7 @@
         final WrappedNetworkMonitor nm = new WrappedNetworkMonitor();
         nm.start();
         setNetworkCapabilities(nm, nc);
-        waitForIdle(nm.getHandler());
+        HandlerUtilsKt.waitForIdle(nm.getHandler(), HANDLER_TIMEOUT_MS);
         mCreatedNetworkMonitors.add(nm);
         return nm;
     }
@@ -437,15 +438,7 @@
 
     private void setNetworkCapabilities(NetworkMonitor nm, NetworkCapabilities nc) {
         nm.notifyNetworkCapabilitiesChanged(nc);
-        waitForIdle(nm.getHandler());
-    }
-
-    private void waitForIdle(Handler handler) {
-        final ConditionVariable cv = new ConditionVariable(false);
-        handler.post(cv::open);
-        if (!cv.block(HANDLER_TIMEOUT_MS)) {
-            fail("Timed out waiting for handler");
-        }
+        HandlerUtilsKt.waitForIdle(nm.getHandler(), HANDLER_TIMEOUT_MS);
     }
 
     @Test
@@ -1125,7 +1118,7 @@
         } catch (RemoteException e) {
             fail("Unexpected exception: " + e);
         }
-        waitForIdle(monitor.getHandler());
+        HandlerUtilsKt.waitForIdle(monitor.getHandler(), HANDLER_TIMEOUT_MS);
 
         return monitor;
     }