Add ConnectivitySettingsManagerTest

- Add tests for ConnectivitySettingsManager.
- Also address leftover javadoc comments.

Bug: 182538166
Test: atest FrameworksNetTests
Test: atest CtsNetTestCases
Change-Id: I8161c1bca84b41964578d59ee5d6ab07b2380707

framework/src/android/net/ConnectivitySettingsManager.java

@@ -562,7 +562,7 @@ public class ConnectivitySettingsManager {
     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 @@ public class ConnectivitySettingsManager {
 
     /**
      * 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 @@ public class ConnectivitySettingsManager {
 
     /**
      * 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 @@ public class ConnectivitySettingsManager {
 
     /**
      * 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.