[ffigen] Fix flaky tests (#1471)

Author: liamappelbe

pkgs/ffigen/test/native_objc_test/arc_test.dart

@@ -7,11 +7,6 @@
 // Objective C support is only available on mac.
 @TestOn('mac-os')
 
-// This test is slightly flaky. Some of the ref counts are occasionally lower
-// than expected, presumably due to the Dart wrapper objects being GC'd before
-// the expect call.
-@Retry(3)
-
 import 'dart:ffi';
 import 'dart:io';
 
@@ -97,6 +92,10 @@ void main() {
       expect(objectRetainCount(obj2raw), 3);
       expect(objectRetainCount(obj3raw), 2);
 
+      expect(obj1, isNotNull); // Force obj1 to stay in scope.
+      expect(obj2, isNotNull); // Force obj2 to stay in scope.
+      expect(obj3, isNotNull); // Force obj3 to stay in scope.
+
       return (obj1raw, obj2raw, obj3raw);
     }
 
@@ -281,21 +280,19 @@ void main() {
       final outerObjRaw = outerObj.pointer;
       expect(objectRetainCount(outerObjRaw), 1);
       final assignObjRaw = assignPropertiesInnerInner(counter, outerObj);
-      expect(objectRetainCount(assignObjRaw), 2);
       doGC();
       // assignObj has been cleaned up.
       expect(counter.value, 1);
       expect(objectRetainCount(assignObjRaw), 0);
       expect(objectRetainCount(outerObjRaw), 1);
+      expect(outerObj, isNotNull); // Force outerObj to stay in scope.
       return (outerObjRaw, assignObjRaw);
     }
 
     test('assign properties ref count correctly', () {
       final counter = calloc<Int32>();
       counter.value = 0;
       final (outerObjRaw, assignObjRaw) = assignPropertiesInner(counter);
-      expect(objectRetainCount(assignObjRaw), 0);
-      expect(objectRetainCount(outerObjRaw), 1);
       doGC();
       expect(counter.value, 0);
       expect(objectRetainCount(assignObjRaw), 0);
@@ -323,12 +320,12 @@ void main() {
       final outerObjRaw = outerObj.pointer;
       expect(objectRetainCount(outerObjRaw), 1);
       final retainObjRaw = retainPropertiesInnerInner(counter, outerObj);
-      expect(objectRetainCount(retainObjRaw), 4);
       doGC();
       // retainObj is still around, because outerObj retains a reference to it.
       expect(objectRetainCount(retainObjRaw), 2);
       expect(objectRetainCount(outerObjRaw), 1);
       expect(counter.value, 2);
+      expect(outerObj, isNotNull); // Force outerObj to stay in scope.
       return (outerObjRaw, retainObjRaw);
     }
 
@@ -339,8 +336,6 @@ void main() {
       // need an autorelease pool.
       final pool = lib.objc_autoreleasePoolPush();
       final (outerObjRaw, retainObjRaw) = retainPropertiesInner(counter);
-      expect(objectRetainCount(retainObjRaw), 2);
-      expect(objectRetainCount(outerObjRaw), 1);
       doGC();
       expect(objectRetainCount(retainObjRaw), 1);
       expect(objectRetainCount(outerObjRaw), 0);

pkgs/ffigen/test/native_objc_test/global_native_test.dart

@@ -43,6 +43,8 @@ void main() {
       final obj2raw = obj2.pointer;
       expect(objectRetainCount(obj2raw), 2); // obj2, and the global variable.
       expect(objectRetainCount(obj1raw), 1); // Just obj1.
+      expect(obj1, isNotNull); // Force obj1 to stay in scope.
+      expect(obj2, isNotNull); // Force obj2 to stay in scope.
 
       return (obj1raw, obj2raw);
     }
@@ -79,6 +81,8 @@ void main() {
       final blk2raw = blk2.pointer;
       expect(blockRetainCount(blk2raw), 2); // blk2, and the global variable.
       expect(blockRetainCount(blk1raw), 1); // Just blk1.
+      expect(blk1, isNotNull); // Force blk1 to stay in scope.
+      expect(blk2, isNotNull); // Force blk2 to stay in scope.
 
       return (blk1raw, blk2raw);
     }

pkgs/ffigen/test/native_objc_test/global_test.dart

@@ -45,6 +45,8 @@ void main() {
       final obj2raw = obj2.pointer;
       expect(objectRetainCount(obj2raw), 2); // obj2, and the global variable.
       expect(objectRetainCount(obj1raw), 1); // Just obj1.
+      expect(obj1, isNotNull); // Force obj1 to stay in scope.
+      expect(obj2, isNotNull); // Force obj2 to stay in scope.
 
       return (obj1raw, obj2raw);
     }
@@ -80,6 +82,8 @@ void main() {
       final blk2raw = blk2.pointer;
       expect(blockRetainCount(blk2raw), 2); // blk2, and the global variable.
       expect(blockRetainCount(blk1raw), 1); // Just blk1.
+      expect(blk1, isNotNull); // Force blk1 to stay in scope.
+      expect(blk2, isNotNull); // Force blk2 to stay in scope.
 
       return (blk1raw, blk2raw);
     }

pkgs/ffigen/test/native_objc_test/ref_count_test.dart

@@ -7,11 +7,6 @@
 // Objective C support is only available on mac.
 @TestOn('mac-os')
 
-// This test is slightly flaky. Some of the ref counts are occasionally lower
-// than expected, presumably due to the Dart wrapper objects being GC'd before
-// the expect call.
-@Retry(3)
-
 import 'dart:ffi';
 import 'dart:io';
 
@@ -98,6 +93,10 @@ void main() {
       expect(objectRetainCount(obj2raw), 3);
       expect(objectRetainCount(obj3raw), 2);
 
+      expect(obj1, isNotNull); // Force obj1 to stay in scope.
+      expect(obj2, isNotNull); // Force obj2 to stay in scope.
+      expect(obj3, isNotNull); // Force obj3 to stay in scope.
+
       return (obj1raw, obj2raw, obj3raw);
     }
 
@@ -282,21 +281,19 @@ void main() {
       final outerObjRaw = outerObj.pointer;
       expect(objectRetainCount(outerObjRaw), 1);
       final assignObjRaw = assignPropertiesInnerInner(counter, outerObj);
-      expect(objectRetainCount(assignObjRaw), 2);
       doGC();
       // assignObj has been cleaned up.
       expect(counter.value, 1);
       expect(objectRetainCount(assignObjRaw), 0);
       expect(objectRetainCount(outerObjRaw), 1);
+      expect(outerObj, isNotNull); // Force outerObj to stay in scope.
       return (outerObjRaw, assignObjRaw);
     }
 
     test('assign properties ref count correctly', () {
       final counter = calloc<Int32>();
       counter.value = 0;
       final (outerObjRaw, assignObjRaw) = assignPropertiesInner(counter);
-      expect(objectRetainCount(assignObjRaw), 0);
-      expect(objectRetainCount(outerObjRaw), 1);
       doGC();
       expect(counter.value, 0);
       expect(objectRetainCount(assignObjRaw), 0);
@@ -324,12 +321,12 @@ void main() {
       final outerObjRaw = outerObj.pointer;
       expect(objectRetainCount(outerObjRaw), 1);
       final retainObjRaw = retainPropertiesInnerInner(counter, outerObj);
-      expect(objectRetainCount(retainObjRaw), 4);
       doGC();
       // retainObj is still around, because outerObj retains a reference to it.
       expect(objectRetainCount(retainObjRaw), 2);
       expect(objectRetainCount(outerObjRaw), 1);
       expect(counter.value, 2);
+      expect(outerObj, isNotNull); // Force outerObj to stay in scope.
       return (outerObjRaw, retainObjRaw);
     }
 
@@ -340,8 +337,6 @@ void main() {
       // need an autorelease pool.
       final pool = lib.objc_autoreleasePoolPush();
       final (outerObjRaw, retainObjRaw) = retainPropertiesInner(counter);
-      expect(objectRetainCount(retainObjRaw), 2);
-      expect(objectRetainCount(outerObjRaw), 1);
       doGC();
       expect(objectRetainCount(retainObjRaw), 1);
       expect(objectRetainCount(outerObjRaw), 0);