1 files changed, 65 insertions, 0 deletions
diff --git a/absl/strings/internal/str_format/extension_test.cc b/absl/strings/internal/str_format/extension_test.cc
new file mode 100644
index 000000000000..224fc923d3e3
--- /dev/null
+++ b/absl/strings/internal/str_format/extension_test.cc
@@ -0,0 +1,65 @@
+//
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "absl/strings/internal/str_format/extension.h"
+
+#include <random>
+#include <string>
+#include "absl/strings/str_format.h"
+
+#include "gtest/gtest.h"
+
+namespace {
+
+std::string MakeRandomString(size_t len) {
+  std::random_device rd;
+  std::mt19937 gen(rd());
+  std::uniform_int_distribution<> dis('a', 'z');
+  std::string s(len, '0');
+  for (char& c : s) {
+    c = dis(gen);
+  }
+  return s;
+}
+
+TEST(FormatExtensionTest, SinkAppendSubstring) {
+  for (size_t chunk_size : {1, 10, 100, 1000, 10000}) {
+    std::string expected, actual;
+    absl::str_format_internal::FormatSinkImpl sink(&actual);
+    for (size_t chunks = 0; chunks < 10; ++chunks) {
+      std::string rand = MakeRandomString(chunk_size);
+      expected += rand;
+      sink.Append(rand);
+    }
+    sink.Flush();
+    EXPECT_EQ(actual, expected);
+  }
+}
+
+TEST(FormatExtensionTest, SinkAppendChars) {
+  for (size_t chunk_size : {1, 10, 100, 1000, 10000}) {
+    std::string expected, actual;
+    absl::str_format_internal::FormatSinkImpl sink(&actual);
+    for (size_t chunks = 0; chunks < 10; ++chunks) {
+      std::string rand = MakeRandomString(1);
+      expected.append(chunk_size, rand[0]);
+      sink.Append(chunk_size, rand[0]);
+    }
+    sink.Flush();
+    EXPECT_EQ(actual, expected);
+  }
+}
+}  // namespace