diff --git a/framework/src/android/net/ConnectivitySettingsManager.java b/framework/src/android/net/ConnectivitySettingsManager.java
index 4644e4f..085de6b 100644
--- a/framework/src/android/net/ConnectivitySettingsManager.java
+++ b/framework/src/android/net/ConnectivitySettingsManager.java
@@ -562,7 +562,7 @@
     public static void setNetworkSwitchNotificationMaximumDailyCount(@NonNull Context context,
             @IntRange(from = 0) int count) {
         if (count < 0) {
-            throw new IllegalArgumentException("Count must be 0~10.");
+            throw new IllegalArgumentException("Count must be more than 0.");
         }
         Settings.Global.putInt(
                 context.getContentResolver(), NETWORK_SWITCH_NOTIFICATION_DAILY_LIMIT, count);
@@ -585,6 +585,7 @@
 
     /**
      * Set minimum duration (to {@link Settings}) between each switching network notifications.
+     * The duration will be rounded down to the next millisecond, and must be positive.
      *
      * @param context The {@link Context} to set the setting.
      * @param duration The minimum duration between notifications when switching networks.
@@ -612,10 +613,11 @@
 
     /**
      * Set URL (to {@link Settings}) used for HTTP captive portal detection upon a new connection.
-     * This URL should respond with a 204 response to a GET request to indicate no captive portal is
-     * present. And this URL must be HTTP as redirect responses are used to find captive portal
-     * sign-in pages. If the URL set to null or be incorrect, it will result in captive portal
-     * detection failed and lost the connection.
+     * The URL is accessed to check for connectivity and presence of a captive portal on a network.
+     * The URL should respond with HTTP status 204 to a GET request, and the stack will use
+     * redirection status as a signal for captive portal detection.
+     * If the URL is set to null or is otherwise incorrect or inaccessible, the stack will fail to
+     * detect connectivity and portals. This will often result in loss of connectivity.
      *
      * @param context The {@link Context} to set the setting.
      * @param url The URL used for HTTP captive portal detection upon a new connection.
@@ -819,6 +821,7 @@
 
     /**
      * Set duration (to {@link Settings}) to keep a PendingIntent-based request.
+     * The duration will be rounded down to the next millisecond, and must be positive.
      *
      * @param context The {@link Context} to set the setting.
      * @param duration The duration to keep a PendingIntent-based request.
diff --git a/tests/common/java/android/net/ConnectivitySettingsManagerTest.kt b/tests/common/java/android/net/ConnectivitySettingsManagerTest.kt
new file mode 100644
index 0000000..ebaa787
--- /dev/null
+++ b/tests/common/java/android/net/ConnectivitySettingsManagerTest.kt
@@ -0,0 +1,295 @@
+/*
+ * Copyright (C) 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.
+ */
+
+package android.net
+
+import android.net.ConnectivitySettingsManager.CAPTIVE_PORTAL_MODE
+import android.net.ConnectivitySettingsManager.CAPTIVE_PORTAL_MODE_AVOID
+import android.net.ConnectivitySettingsManager.CAPTIVE_PORTAL_MODE_IGNORE
+import android.net.ConnectivitySettingsManager.CAPTIVE_PORTAL_MODE_PROMPT
+import android.net.ConnectivitySettingsManager.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS
+import android.net.ConnectivitySettingsManager.DATA_ACTIVITY_TIMEOUT_MOBILE
+import android.net.ConnectivitySettingsManager.DATA_ACTIVITY_TIMEOUT_WIFI
+import android.net.ConnectivitySettingsManager.DNS_RESOLVER_MAX_SAMPLES
+import android.net.ConnectivitySettingsManager.DNS_RESOLVER_MIN_SAMPLES
+import android.net.ConnectivitySettingsManager.DNS_RESOLVER_SAMPLE_VALIDITY_SECONDS
+import android.net.ConnectivitySettingsManager.DNS_RESOLVER_SUCCESS_THRESHOLD_PERCENT
+import android.net.ConnectivitySettingsManager.MOBILE_DATA_ALWAYS_ON
+import android.net.ConnectivitySettingsManager.NETWORK_SWITCH_NOTIFICATION_DAILY_LIMIT
+import android.net.ConnectivitySettingsManager.NETWORK_SWITCH_NOTIFICATION_RATE_LIMIT_MILLIS
+import android.net.ConnectivitySettingsManager.PRIVATE_DNS_DEFAULT_MODE
+import android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE_OFF
+import android.net.ConnectivitySettingsManager.PRIVATE_DNS_MODE_OPPORTUNISTIC
+import android.net.ConnectivitySettingsManager.WIFI_ALWAYS_REQUESTED
+import android.net.ConnectivitySettingsManager.getCaptivePortalMode
+import android.net.ConnectivitySettingsManager.getConnectivityKeepPendingIntentDuration
+import android.net.ConnectivitySettingsManager.getDnsResolverSampleRanges
+import android.net.ConnectivitySettingsManager.getDnsResolverSampleValidityDuration
+import android.net.ConnectivitySettingsManager.getDnsResolverSuccessThresholdPercent
+import android.net.ConnectivitySettingsManager.getMobileDataActivityTimeout
+import android.net.ConnectivitySettingsManager.getMobileDataAlwaysOn
+import android.net.ConnectivitySettingsManager.getNetworkSwitchNotificationMaximumDailyCount
+import android.net.ConnectivitySettingsManager.getNetworkSwitchNotificationRateDuration
+import android.net.ConnectivitySettingsManager.getPrivateDnsDefaultMode
+import android.net.ConnectivitySettingsManager.getWifiAlwaysRequested
+import android.net.ConnectivitySettingsManager.getWifiDataActivityTimeout
+import android.net.ConnectivitySettingsManager.setCaptivePortalMode
+import android.net.ConnectivitySettingsManager.setConnectivityKeepPendingIntentDuration
+import android.net.ConnectivitySettingsManager.setDnsResolverSampleRanges
+import android.net.ConnectivitySettingsManager.setDnsResolverSampleValidityDuration
+import android.net.ConnectivitySettingsManager.setDnsResolverSuccessThresholdPercent
+import android.net.ConnectivitySettingsManager.setMobileDataActivityTimeout
+import android.net.ConnectivitySettingsManager.setMobileDataAlwaysOn
+import android.net.ConnectivitySettingsManager.setNetworkSwitchNotificationMaximumDailyCount
+import android.net.ConnectivitySettingsManager.setNetworkSwitchNotificationRateDuration
+import android.net.ConnectivitySettingsManager.setPrivateDnsDefaultMode
+import android.net.ConnectivitySettingsManager.setWifiAlwaysRequested
+import android.net.ConnectivitySettingsManager.setWifiDataActivityTimeout
+import android.os.Build
+import android.platform.test.annotations.AppModeFull
+import android.provider.Settings
+import android.util.Range
+import androidx.test.InstrumentationRegistry
+import androidx.test.filters.SmallTest
+import com.android.net.module.util.ConnectivitySettingsUtils.getPrivateDnsModeAsString
+import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
+import com.android.testutils.DevSdkIgnoreRunner
+import junit.framework.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import java.time.Duration
+import java.util.Objects
+import kotlin.test.assertFailsWith
+
+/**
+ * Tests for [ConnectivitySettingsManager].
+ *
+ * Build, install and run with:
+ * atest android.net.ConnectivitySettingsManagerTest
+ */
+@RunWith(DevSdkIgnoreRunner::class)
+@IgnoreUpTo(Build.VERSION_CODES.R)
+@SmallTest
+@AppModeFull(reason = "WRITE_SECURE_SETTINGS permission can't be granted to instant apps")
+class ConnectivitySettingsManagerTest {
+    private val instrumentation = InstrumentationRegistry.getInstrumentation()
+    private val context = instrumentation.context
+    private val resolver = context.contentResolver
+
+    private val defaultDuration = Duration.ofSeconds(0L)
+    private val testTime1 = 5L
+    private val testTime2 = 10L
+    private val settingsTypeGlobal = "global"
+    private val settingsTypeSecure = "secure"
+
+    /*** Reset setting value or delete setting if the setting was not existed before testing. */
+    private fun resetSettings(names: Array<String>, type: String, values: Array<String?>) {
+        for (i in names.indices) {
+            if (Objects.equals(values[i], null)) {
+                instrumentation.uiAutomation.executeShellCommand(
+                        "settings delete $type ${names[i]}")
+            } else {
+                if (settingsTypeSecure.equals(type)) {
+                    Settings.Secure.putString(resolver, names[i], values[i])
+                } else {
+                    Settings.Global.putString(resolver, names[i], values[i])
+                }
+            }
+        }
+    }
+
+    fun <T> testIntSetting(
+        names: Array<String>,
+        type: String,
+        value1: T,
+        value2: T,
+        getter: () -> T,
+        setter: (value: T) -> Unit,
+        testIntValues: IntArray
+    ) {
+        val originals: Array<String?> = Array(names.size) { i ->
+            if (settingsTypeSecure.equals(type)) {
+                Settings.Secure.getString(resolver, names[i])
+            } else {
+                Settings.Global.getString(resolver, names[i])
+            }
+        }
+
+        try {
+            for (i in names.indices) {
+                if (settingsTypeSecure.equals(type)) {
+                    Settings.Secure.putString(resolver, names[i], testIntValues[i].toString())
+                } else {
+                    Settings.Global.putString(resolver, names[i], testIntValues[i].toString())
+                }
+            }
+            assertEquals(value1, getter())
+
+            setter(value2)
+            assertEquals(value2, getter())
+        } finally {
+            resetSettings(names, type, originals)
+        }
+    }
+
+    @Test
+    fun testMobileDataActivityTimeout() {
+        testIntSetting(names = arrayOf(DATA_ACTIVITY_TIMEOUT_MOBILE), type = settingsTypeGlobal,
+                value1 = Duration.ofSeconds(testTime1), value2 = Duration.ofSeconds(testTime2),
+                getter = { getMobileDataActivityTimeout(context, defaultDuration) },
+                setter = { setMobileDataActivityTimeout(context, it) },
+                testIntValues = intArrayOf(testTime1.toInt()))
+    }
+
+    @Test
+    fun testWifiDataActivityTimeout() {
+        testIntSetting(names = arrayOf(DATA_ACTIVITY_TIMEOUT_WIFI), type = settingsTypeGlobal,
+                value1 = Duration.ofSeconds(testTime1), value2 = Duration.ofSeconds(testTime2),
+                getter = { getWifiDataActivityTimeout(context, defaultDuration) },
+                setter = { setWifiDataActivityTimeout(context, it) },
+                testIntValues = intArrayOf(testTime1.toInt()))
+    }
+
+    @Test
+    fun testDnsResolverSampleValidityDuration() {
+        testIntSetting(names = arrayOf(DNS_RESOLVER_SAMPLE_VALIDITY_SECONDS),
+                type = settingsTypeGlobal, value1 = Duration.ofSeconds(testTime1),
+                value2 = Duration.ofSeconds(testTime2),
+                getter = { getDnsResolverSampleValidityDuration(context, defaultDuration) },
+                setter = { setDnsResolverSampleValidityDuration(context, it) },
+                testIntValues = intArrayOf(testTime1.toInt()))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setDnsResolverSampleValidityDuration(context, Duration.ofSeconds(-1L)) }
+    }
+
+    @Test
+    fun testDnsResolverSuccessThresholdPercent() {
+        testIntSetting(names = arrayOf(DNS_RESOLVER_SUCCESS_THRESHOLD_PERCENT),
+                type = settingsTypeGlobal, value1 = 5, value2 = 10,
+                getter = { getDnsResolverSuccessThresholdPercent(context, 0 /* def */) },
+                setter = { setDnsResolverSuccessThresholdPercent(context, it) },
+                testIntValues = intArrayOf(5))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setDnsResolverSuccessThresholdPercent(context, -1) }
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setDnsResolverSuccessThresholdPercent(context, 120) }
+    }
+
+    @Test
+    fun testDnsResolverSampleRanges() {
+        testIntSetting(names = arrayOf(DNS_RESOLVER_MIN_SAMPLES, DNS_RESOLVER_MAX_SAMPLES),
+                type = settingsTypeGlobal, value1 = Range(1, 63), value2 = Range(2, 62),
+                getter = { getDnsResolverSampleRanges(context) },
+                setter = { setDnsResolverSampleRanges(context, it) },
+                testIntValues = intArrayOf(1, 63))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setDnsResolverSampleRanges(context, Range(-1, 62)) }
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setDnsResolverSampleRanges(context, Range(2, 65)) }
+    }
+
+    @Test
+    fun testNetworkSwitchNotificationMaximumDailyCount() {
+        testIntSetting(names = arrayOf(NETWORK_SWITCH_NOTIFICATION_DAILY_LIMIT),
+                type = settingsTypeGlobal, value1 = 5, value2 = 15,
+                getter = { getNetworkSwitchNotificationMaximumDailyCount(context, 0 /* def */) },
+                setter = { setNetworkSwitchNotificationMaximumDailyCount(context, it) },
+                testIntValues = intArrayOf(5))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setNetworkSwitchNotificationMaximumDailyCount(context, -1) }
+    }
+
+    @Test
+    fun testNetworkSwitchNotificationRateDuration() {
+        testIntSetting(names = arrayOf(NETWORK_SWITCH_NOTIFICATION_RATE_LIMIT_MILLIS),
+                type = settingsTypeGlobal, value1 = Duration.ofMillis(testTime1),
+                value2 = Duration.ofMillis(testTime2),
+                getter = { getNetworkSwitchNotificationRateDuration(context, defaultDuration) },
+                setter = { setNetworkSwitchNotificationRateDuration(context, it) },
+                testIntValues = intArrayOf(testTime1.toInt()))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setNetworkSwitchNotificationRateDuration(context, Duration.ofMillis(-1L)) }
+    }
+
+    @Test
+    fun testCaptivePortalMode() {
+        testIntSetting(names = arrayOf(CAPTIVE_PORTAL_MODE), type = settingsTypeGlobal,
+                value1 = CAPTIVE_PORTAL_MODE_AVOID, value2 = CAPTIVE_PORTAL_MODE_PROMPT,
+                getter = { getCaptivePortalMode(context, CAPTIVE_PORTAL_MODE_IGNORE) },
+                setter = { setCaptivePortalMode(context, it) },
+                testIntValues = intArrayOf(CAPTIVE_PORTAL_MODE_AVOID))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setCaptivePortalMode(context, 5 /* mode */) }
+    }
+
+    @Test
+    fun testPrivateDnsDefaultMode() {
+        val original = Settings.Global.getString(resolver, PRIVATE_DNS_DEFAULT_MODE)
+
+        try {
+            val mode = getPrivateDnsModeAsString(PRIVATE_DNS_MODE_OPPORTUNISTIC)
+            Settings.Global.putString(resolver, PRIVATE_DNS_DEFAULT_MODE, mode)
+            assertEquals(mode, getPrivateDnsDefaultMode(context))
+
+            setPrivateDnsDefaultMode(context, PRIVATE_DNS_MODE_OFF)
+            assertEquals(getPrivateDnsModeAsString(PRIVATE_DNS_MODE_OFF),
+                    getPrivateDnsDefaultMode(context))
+        } finally {
+            resetSettings(names = arrayOf(PRIVATE_DNS_DEFAULT_MODE), type = settingsTypeGlobal,
+                    values = arrayOf(original))
+        }
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setPrivateDnsDefaultMode(context, -1) }
+    }
+
+    @Test
+    fun testConnectivityKeepPendingIntentDuration() {
+        testIntSetting(names = arrayOf(CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS),
+                type = settingsTypeSecure, value1 = Duration.ofMillis(testTime1),
+                value2 = Duration.ofMillis(testTime2),
+                getter = { getConnectivityKeepPendingIntentDuration(context, defaultDuration) },
+                setter = { setConnectivityKeepPendingIntentDuration(context, it) },
+                testIntValues = intArrayOf(testTime1.toInt()))
+
+        assertFailsWith<IllegalArgumentException>("Expect fail but argument accepted.") {
+            setConnectivityKeepPendingIntentDuration(context, Duration.ofMillis(-1L)) }
+    }
+
+    @Test
+    fun testMobileDataAlwaysOn() {
+        testIntSetting(names = arrayOf(MOBILE_DATA_ALWAYS_ON), type = settingsTypeGlobal,
+                value1 = false, value2 = true,
+                getter = { getMobileDataAlwaysOn(context, true /* def */) },
+                setter = { setMobileDataAlwaysOn(context, it) },
+                testIntValues = intArrayOf(0))
+    }
+
+    @Test
+    fun testWifiAlwaysRequested() {
+        testIntSetting(names = arrayOf(WIFI_ALWAYS_REQUESTED), type = settingsTypeGlobal,
+                value1 = false, value2 = true,
+                getter = { getWifiAlwaysRequested(context, true /* def */) },
+                setter = { setWifiAlwaysRequested(context, it) },
+                testIntValues = intArrayOf(0))
+    }
+}
\ No newline at end of file