Fix the conditions of copying/inserting dictionary entries. Previously they would reject feasible mutations in edge cases.

PiperOrigin-RevId: 551018646

e2e_tests/functional_test.cc

diff --git a/e2e_tests/functional_test.cc b/e2e_tests/functional_test.cc
index 0e78f2f..d7c5b6a 100644
--- a/e2e_tests/functional_test.cc
+++ b/e2e_tests/functional_test.cc
@@ -744,6 +744,13 @@
   EXPECT_THAT(status, Eq(Signal(SIGABRT)));
 }
 
+TEST_F(FuzzingModeTest, FixedSizeVectorValueTestFindsAbortInFuzzingMode) {
+  auto [status, std_out, std_err] =
+      RunWith("--fuzz=MySuite.FixedSizeVectorValue");
+  EXPECT_THAT(std_err, HasSubstr("argument 0: {'F'"));
+  EXPECT_THAT(status, Eq(Signal(SIGABRT)));
+}
+
 TEST_F(FuzzingModeTest, GoogleTestExpectationsStopTheFuzzer) {
   auto [status, std_out, std_err] =
       RunWith("--fuzz=MySuite.GoogleTestExpect");

e2e_tests/testdata/fuzz_tests_for_microbenchmarking.cc

diff --git a/e2e_tests/testdata/fuzz_tests_for_microbenchmarking.cc b/e2e_tests/testdata/fuzz_tests_for_microbenchmarking.cc
index 825e05f..399903e 100644
--- a/e2e_tests/testdata/fuzz_tests_for_microbenchmarking.cc
+++ b/e2e_tests/testdata/fuzz_tests_for_microbenchmarking.cc
@@ -213,6 +213,10 @@
 }
 FUZZ_TEST(MySuite, VectorValue);
 
+constexpr auto& FixedSizeVectorValue = VectorValue;
+FUZZ_TEST(MySuite, FixedSizeVectorValue)
+    .WithDomains(fuzztest::VectorOf(fuzztest::Arbitrary<char>()).WithSize(4));
+
 __attribute__((optnone)) void WithDomainClass(uint8_t a, double d) {
   // This will only crash with a=10, to make it easier to check the results.
   // d can have any value.

fuzztest/internal/domains/container_mutation_helpers.h

diff --git a/fuzztest/internal/domains/container_mutation_helpers.h b/fuzztest/internal/domains/container_mutation_helpers.h
index 6de1ce5..c6c17de 100644
--- a/fuzztest/internal/domains/container_mutation_helpers.h
+++ b/fuzztest/internal/domains/container_mutation_helpers.h
@@ -117,7 +117,7 @@
 bool CopyFromDictionaryEntry(const DictionaryEntry<ContainerT>& dict_entry,
                              absl::BitGenRef prng, ContainerT& val,
                              size_t max_size) {
-  if (dict_entry.value.size() >= max_size) return false;
+  if (dict_entry.value.size() > max_size) return false;
   size_t position_hint = GetOrGuessPositionHint(
       dict_entry.position_hint,
       std::min(val.size(), max_size - dict_entry.value.size()), prng);
@@ -132,7 +132,7 @@
     const DictionaryEntry<ContainerT>& dict_entry, absl::BitGenRef prng,
     ContainerT& val, size_t max_size,
     std::optional<DictionaryEntry<ContainerT>>& permanent_dict_candidate) {
-  if (dict_entry.value.size() >= max_size) return false;
+  if (dict_entry.value.size() > max_size) return false;
   size_t position_hint = GetOrGuessPositionHint(
       dict_entry.position_hint,
       std::min(val.size(), max_size - dict_entry.value.size()), prng);
@@ -153,7 +153,7 @@
 bool InsertFromDictionaryEntry(const DictionaryEntry<ContainerT>& dict_entry,
                                absl::BitGenRef prng, ContainerT& val,
                                size_t max_size) {
-  if (dict_entry.value.size() >= max_size) return false;
+  if (val.size() + dict_entry.value.size() > max_size) return false;
   size_t position_hint =
       GetOrGuessPositionHint(dict_entry.position_hint, val.size(), prng);
   return InsertPart<is_self>(dict_entry.value, val, 0, dict_entry.value.size(),
@@ -167,7 +167,7 @@
     const DictionaryEntry<ContainerT>& dict_entry, absl::BitGenRef prng,
     ContainerT& val, size_t max_size,
     std::optional<DictionaryEntry<ContainerT>>& permanent_dict_candidate) {
-  if (dict_entry.value.size() >= max_size) return false;
+  if (val.size() + dict_entry.value.size() > max_size) return false;
   size_t position_hint =
       GetOrGuessPositionHint(dict_entry.position_hint, val.size(), prng);
   bool mutated =