Add a "variant: " prefix to variant descriptions in test names (#86701)

packages/flutter_test/lib/src/widget_tester.dart

@@ -149,7 +149,13 @@ void testWidgets(
   final WidgetTester tester = WidgetTester._(binding);
   for (final dynamic value in variant.values) {
     final String variationDescription = variant.describeValue(value);
-    final String combinedDescription = variationDescription.isNotEmpty ? '$description ($variationDescription)' : description;
+    // IDEs may make assumptions about the format of this suffix in order to
+    // support running tests directly from the editor (where they may have
+    // access to only the test name, provided by the analysis server).
+    // See https://github.com/flutter/flutter/issues/86659.
+    final String combinedDescription = variationDescription.isNotEmpty
+        ? '$description (variant: $variationDescription)'
+        : description;
     test(
       combinedDescription,
       () {

packages/flutter_test/test/widget_tester_test.dart

@@ -697,7 +697,10 @@ void main() {
       if (debugDefaultTargetPlatformOverride == null) {
         expect(tester.testDescription, equals('variant tests have descriptions with details'));
       } else {
-        expect(tester.testDescription, equals('variant tests have descriptions with details ($debugDefaultTargetPlatformOverride)'));
+        expect(
+          tester.testDescription,
+          equals('variant tests have descriptions with details (variant: $debugDefaultTargetPlatformOverride)'),
+        );
       }
     }, variant: TargetPlatformVariant(TargetPlatform.values.toSet()));
   });