Fixes #2158. Fix flaky co19_2/LibTest/isolate/Isolate/pause_A01_t01, _02 tests (#2159)

Author: sgrekhov

LibTest/isolate/Isolate/pause_A01_t01.dart

@@ -17,39 +17,47 @@
 ///
 /// @author [email protected]
 
+import "dart:io";
 import "dart:isolate";
 import "dart:math";
 import "../../../Utils/expect.dart";
 
 // indefinitely running isolate
-entryPoint(SendPort sendPort){
+entryPoint(List<SendPort> sendPorts) {
+  sendPorts[0].send(42);
   Random random = new Random();
   int s = 0;
-  while (true){
+  while (true) {
     s = -s + random.nextInt(100);
-    sendPort.send(s);
+    sendPorts[1].send(s);
+
+    // Synchronous sleep does not yield to the message loop, so the pause
+    // doesn't take effect.
+    sleep(const Duration(milliseconds: 1));
   }
 }
 
 test() async {
-  ReceivePort receivePort = new ReceivePort();
+  ReceivePort receivePort1 = new ReceivePort();
+  ReceivePort receivePort2 = new ReceivePort();
   ReceivePort onExit = new ReceivePort();
-  Isolate isolate = await Isolate.spawn(
-      entryPoint,
-      receivePort.sendPort, // message
-      onExit:onExit.sendPort,
-      errorsAreFatal:true
-  );
+  Isolate isolate =
+      await Isolate.spawn(entryPoint,
+          [receivePort1.sendPort, receivePort2.sendPort],
+          onExit: onExit.sendPort,
+          errorsAreFatal: true);
+  // make sure that isolate started its work
+  await receivePort1.first;
   isolate.pause();
   // check that messages are received from paused isolate
   int count = 0;
-  await for (var _ in receivePort){
-    if (count++==1000000){
+  await for (var _ in receivePort2) {
+    if (count++ == 100) {
       break;
     }
   }
   // clean up
-  isolate.kill(priority:Isolate.immediate);
+  isolate.kill(priority: Isolate.immediate);
   await onExit.first;
   asyncEnd();
 }

LibTest/isolate/Isolate/pause_A01_t02.dart

@@ -18,39 +18,47 @@
 ///
 /// @author [email protected]
 
+import "dart:io";
 import "dart:isolate";
 import "dart:math";
 import "../../../Utils/expect.dart";
 
 // indefinitely running isolate
-entryPoint(SendPort sendPort){
+entryPoint(List<SendPort> sendPorts) {
+  sendPorts[0].send(42);
   Random random = new Random();
   int s = 0;
-  while (true){
+  while (true) {
     s = -s + random.nextInt(100);
-    sendPort.send(s);
+    sendPorts[1].send(s);
+
+    // Synchronous sleep does not yield to the message loop, so the pause
+    // doesn't take effect.
+    sleep(const Duration(milliseconds: 1));
   }
 }
 
 test() async {
-  ReceivePort receivePort = new ReceivePort();
+  ReceivePort receivePort1 = new ReceivePort();
+  ReceivePort receivePort2 = new ReceivePort();
   ReceivePort onExit = new ReceivePort();
-  Isolate isolate = await Isolate.spawn(
-      entryPoint,
-      receivePort.sendPort, // message
-      onExit:onExit.sendPort,
-      errorsAreFatal:true
-  );
+  Isolate isolate =
+      await Isolate.spawn(entryPoint,
+          [receivePort1.sendPort, receivePort2.sendPort],
+          onExit: onExit.sendPort,
+          errorsAreFatal: true);
+  // make sure that isolate started its work
+  await receivePort1.first;
   isolate.pause(new Capability());
   // check that messages are received from paused isolate
   int count = 0;
-  await for (var _ in receivePort){
-    if (count++==1000000){
+  await for (var _ in receivePort2) {
+    if (count++ == 100) {
       break;
     }
   }
   // clean up
-  isolate.kill(priority:Isolate.immediate);
+  isolate.kill(priority: Isolate.immediate);
   await onExit.first;
   asyncEnd();
 }