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PiperOrigin-RevId: 914157591

domain_tests/container_test.cc

diff --git a/domain_tests/container_test.cc b/domain_tests/container_test.cc
index c599fa4..d665ed7 100644
--- a/domain_tests/container_test.cc
+++ b/domain_tests/container_test.cc
@@ -247,15 +247,29 @@
   EXPECT_TRUE(domain_soft.ValidateCorpusValue(*corpus_val_soft).ok());
 }
 
-TEST(ContainerDeathTest, MutationAbortsWhenSizeExceedsMaxSize) {
+TEST(ContainerTest,
+     MutationDoesNotAbortWhenSizeExceedsMaxSizeButEnforcesShrink) {
   auto domain_hard = Arbitrary<std::vector<int>>().WithMaxSize(2);
   std::vector<int> value = {1, 2, 3};
   Value val(domain_hard, value);
   absl::BitGen bitgen;
 
-  EXPECT_DEATH(
-      val.Mutate(domain_hard, bitgen, /*metadata=*/{}, /*only_shrink=*/false),
-      "Size 3 is not between 0 and 2");
+  // Should not crash, despite size 3 > max_size 2.
+  val.Mutate(domain_hard, bitgen, /*metadata=*/{}, /*only_shrink=*/false);
+
+  // Size should not have grown.
+  EXPECT_LE(val.user_value.size(), 3);
+
+  // If we mutate enough times, it should eventually shrink to <= 2.
+  bool shrunk = false;
+  for (int i = 0; i < 1000; ++i) {
+    val.Mutate(domain_hard, bitgen, /*metadata=*/{}, /*only_shrink=*/false);
+    if (val.user_value.size() <= 2) {
+      shrunk = true;
+      break;
+    }
+  }
+  EXPECT_TRUE(shrunk);
 }
 
 TEST(ContainerTest, WithSoftMaxSizeMutationDoesNotGrowIfSizeExceedsLimit) {

fuzztest/internal/domains/container_of_impl.h

diff --git a/fuzztest/internal/domains/container_of_impl.h b/fuzztest/internal/domains/container_of_impl.h
index 7a8cd45..ca8286d 100644
--- a/fuzztest/internal/domains/container_of_impl.h
+++ b/fuzztest/internal/domains/container_of_impl.h
@@ -114,14 +114,10 @@
               const domain_implementor::MutationMetadata& metadata,
               bool only_shrink) {
     permanent_dict_candidate_ = std::nullopt;
-    if (!validate_max_size()) {
-      FUZZTEST_CHECK(min_size() <= val.size())
-          << "Size " << val.size() << " is smaller than min size "
-          << min_size();
-    } else {
-      FUZZTEST_CHECK(min_size() <= val.size() && val.size() <= max_size())
-          << "Size " << val.size() << " is not between " << min_size()
-          << " and " << max_size();
+    FUZZTEST_CHECK(min_size() <= val.size())
+        << "Size " << val.size() << " is smaller than min size " << min_size();
+    if (validate_max_size() && val.size() > max_size()) {
+      only_shrink = true;
     }
 
     const bool can_shrink = val.size() > min_size();