diff --git a/quic/api/test/IoBufQuicBatchTest.cpp b/quic/api/test/IoBufQuicBatchTest.cpp
index 1d3000724..93d97e6d0 100644
--- a/quic/api/test/IoBufQuicBatchTest.cpp
+++ b/quic/api/test/IoBufQuicBatchTest.cpp
@@ -18,8 +18,7 @@
 constexpr const auto kNumLoops = 64;
 constexpr const auto kMaxBufs = 10;
 
-namespace quic {
-namespace testing {
+namespace quic::testing {
 void RunTest(int numBatch) {
   folly::EventBase evb;
   std::shared_ptr<FollyQuicEventBase> qEvb =
@@ -62,5 +61,4 @@ TEST(QuicBatch, TestBatchingNoFlush) {
 TEST(QuicBatch, TestBatching) {
   RunTest(kMaxBufs);
 }
-} // namespace testing
-} // namespace quic
+} // namespace quic::testing
diff --git a/quic/api/test/QuicBatchWriterTest.cpp b/quic/api/test/QuicBatchWriterTest.cpp
index 431cb7f90..f3799d2f8 100644
--- a/quic/api/test/QuicBatchWriterTest.cpp
+++ b/quic/api/test/QuicBatchWriterTest.cpp
@@ -18,8 +18,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace testing {
+namespace quic::testing {
 
 constexpr const auto kStrLen = 10;
 constexpr const auto kStrLenGT = 20;
@@ -864,5 +863,4 @@ TEST_F(SinglePacketBackpressureBatchWriterTest, TestFailedWriteCachedOnEAGAIN) {
   EXPECT_FALSE(conn_.pendingWriteBatch_.buf);
 }
 
-} // namespace testing
-} // namespace quic
+} // namespace quic::testing
diff --git a/quic/api/test/QuicPacketSchedulerTest.cpp b/quic/api/test/QuicPacketSchedulerTest.cpp
index 14a6f7d91..c8c5edf84 100644
--- a/quic/api/test/QuicPacketSchedulerTest.cpp
+++ b/quic/api/test/QuicPacketSchedulerTest.cpp
@@ -105,8 +105,7 @@ PacketNum addOutstandingPacket(QuicConnectionStateBase& conn) {
 
 } // namespace
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicPacketSchedulerTest : public testing::Test {
  public:
@@ -2730,5 +2729,4 @@ TEST_F(QuicPacketSchedulerTest, ImmediateAckFrameSchedulerNotRequested) {
   EXPECT_LT(packetLength, conn.udpSendPacketLen);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/api/test/QuicTransportBaseTest.cpp b/quic/api/test/QuicTransportBaseTest.cpp
index 265b84ce7..b05515acc 100644
--- a/quic/api/test/QuicTransportBaseTest.cpp
+++ b/quic/api/test/QuicTransportBaseTest.cpp
@@ -31,8 +31,7 @@
 using namespace testing;
 using namespace folly;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 constexpr uint8_t kStreamIncrement = 0x04;
 using ByteEvent = QuicTransportBase::ByteEvent;
@@ -5093,5 +5092,4 @@ TEST_P(QuicTransportImplTestBase, TestCheckIdleTimerTimerActiveConnExpired) {
   transport.reset();
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/api/test/QuicTransportFunctionsTest.cpp b/quic/api/test/QuicTransportFunctionsTest.cpp
index 4b22a9198..00679556a 100644
--- a/quic/api/test/QuicTransportFunctionsTest.cpp
+++ b/quic/api/test/QuicTransportFunctionsTest.cpp
@@ -24,8 +24,7 @@
 using namespace folly;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 using PacketStreamDetails = OutstandingPacketMetadata::StreamDetails;
 
@@ -4842,5 +4841,4 @@ TEST_F(QuicTransportFunctionsTest, onQuicStreamClosed) {
   EXPECT_EQ(conn->streamManager->streamCount(), 0);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/api/test/QuicTransportTest.cpp b/quic/api/test/QuicTransportTest.cpp
index 26e056227..c5e0f945c 100644
--- a/quic/api/test/QuicTransportTest.cpp
+++ b/quic/api/test/QuicTransportTest.cpp
@@ -34,8 +34,7 @@ using namespace folly;
 // using namespace folly::test;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 /**
  * A DeliveryCallback that closes your transport when it's canceled, or when
@@ -5445,5 +5444,4 @@ TEST_F(QuicTransportTest, ValidateL4SFailure) {
   }
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/client/test/Mocks.h b/quic/client/test/Mocks.h
index 139a3d68e..247623de0 100644
--- a/quic/client/test/Mocks.h
+++ b/quic/client/test/Mocks.h
@@ -18,8 +18,7 @@
 #include <quic/handshake/CryptoFactory.h>
 #include <quic/handshake/TransportParameters.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockClientHandshakeFactory : public ClientHandshakeFactory {
  public:
@@ -136,5 +135,4 @@ class MockQuicClientTransport : public quic::QuicClientTransport {
   TestType testType_;
 };
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/DecodeTest.cpp b/quic/codec/test/DecodeTest.cpp
index 9c0562af9..4b578200d 100644
--- a/quic/codec/test/DecodeTest.cpp
+++ b/quic/codec/test/DecodeTest.cpp
@@ -18,8 +18,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 using UnderlyingFrameType = std::underlying_type<FrameType>::type;
 
@@ -924,5 +923,4 @@ TEST_F(DecodeTest, AckFrequencyFrameDecodeInvalidReserved) {
   EXPECT_THROW(decodeAckFrequencyFrame(cursor), QuicTransportException);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/Mocks.h b/quic/codec/test/Mocks.h
index ad156cafa..d9830c591 100644
--- a/quic/codec/test/Mocks.h
+++ b/quic/codec/test/Mocks.h
@@ -12,8 +12,7 @@
 #include <quic/codec/QuicPacketBuilder.h>
 #include <quic/common/test/TestUtils.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockConnectionIdAlgo : public ConnectionIdAlgo {
  public:
@@ -145,5 +144,4 @@ class MockQuicPacketBuilder : public PacketBuilderInterface {
   std::unique_ptr<folly::IOBuf> data_{folly::IOBuf::create(100)};
   BufAppender appender_{data_.get(), 100};
 };
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/PacketNumberTest.cpp b/quic/codec/test/PacketNumberTest.cpp
index 5712fcd70..275490e56 100644
--- a/quic/codec/test/PacketNumberTest.cpp
+++ b/quic/codec/test/PacketNumberTest.cpp
@@ -12,8 +12,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct Packet8DecodeData {
   PacketNum largestReceivedUdpPacketNum;
@@ -105,5 +104,4 @@ TEST_F(EncodingTest, Draft17Example) {
   EXPECT_EQ(3, encodePacketNumber(0xace8fe, 0xabe8bc).length);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/QuicConnectionIdTest.cpp b/quic/codec/test/QuicConnectionIdTest.cpp
index b1c0a82ad..82a7db120 100644
--- a/quic/codec/test/QuicConnectionIdTest.cpp
+++ b/quic/codec/test/QuicConnectionIdTest.cpp
@@ -11,8 +11,7 @@
 
 #include <folly/portability/GTest.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 TEST(ConnectionIdTest, TestConnidLen) {
   std::string out = folly::unhexlify("ffaabbee00");
@@ -62,5 +61,4 @@ TEST(ConnectionIdTest, ConnIdSize) {
   EXPECT_NO_THROW(ConnectionId{testconnid});
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/QuicHeaderCodecTest.cpp b/quic/codec/test/QuicHeaderCodecTest.cpp
index 9c622450f..9a9e3351d 100644
--- a/quic/codec/test/QuicHeaderCodecTest.cpp
+++ b/quic/codec/test/QuicHeaderCodecTest.cpp
@@ -14,8 +14,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicHeaderCodecTest : public Test {};
 
@@ -61,5 +60,4 @@ TEST_F(QuicHeaderCodecTest, ShortHeaderTest) {
     EXPECT_EQ(getTestConnectionId(), header->asShort()->getConnectionId());
   }
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/QuicIntegerTest.cpp b/quic/codec/test/QuicIntegerTest.cpp
index f65419ef9..ac97ad551 100644
--- a/quic/codec/test/QuicIntegerTest.cpp
+++ b/quic/codec/test/QuicIntegerTest.cpp
@@ -17,8 +17,7 @@
 using namespace testing;
 using namespace folly;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct IntegerParams {
   uint64_t decoded;
@@ -150,5 +149,4 @@ INSTANTIATE_TEST_SUITE_P(
         IntegerParams({37, "25", false}),
         IntegerParams({std::numeric_limits<uint64_t>::max(), "25", true})));
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/QuicPacketRebuilderTest.cpp b/quic/codec/test/QuicPacketRebuilderTest.cpp
index 8337eb04e..734a8edea 100644
--- a/quic/codec/test/QuicPacketRebuilderTest.cpp
+++ b/quic/codec/test/QuicPacketRebuilderTest.cpp
@@ -22,8 +22,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 OutstandingPacketWrapper makeDummyOutstandingPacket(
     const RegularQuicWritePacket& writePacket,
@@ -695,5 +694,4 @@ TEST_F(QuicPacketRebuilderTest, LastStreamFrameFinOnlySkipLen) {
   PacketRebuilder rebuilder(mockBuilder, conn);
   EXPECT_TRUE(rebuilder.rebuildFromPacket(outstandingPacket).has_value());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/QuicWriteCodecTest.cpp b/quic/codec/test/QuicWriteCodecTest.cpp
index dddb1804a..f9ed25f8d 100644
--- a/quic/codec/test/QuicWriteCodecTest.cpp
+++ b/quic/codec/test/QuicWriteCodecTest.cpp
@@ -52,8 +52,7 @@ QuicFrame parseQuicFrame(
           receiveTimeStampsConfig));
 }
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 void setupCommonExpects(MockQuicPacketBuilder& pktBuilder) {
   EXPECT_CALL(pktBuilder, remainingSpaceInPkt()).WillRepeatedly(Invoke([&]() {
@@ -2434,5 +2433,4 @@ INSTANTIATE_TEST_SUITE_P(
         FrameType::ACK_RECEIVE_TIMESTAMPS));
 // Values(FrameType::ACK, FrameType::ACK_ECN,
 // FrameType::ACK_RECEIVE_TIMESTAMPS));
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/ServerConnectionIdParamsTest.cpp b/quic/codec/test/ServerConnectionIdParamsTest.cpp
index 07c9e1659..160b3177f 100644
--- a/quic/codec/test/ServerConnectionIdParamsTest.cpp
+++ b/quic/codec/test/ServerConnectionIdParamsTest.cpp
@@ -8,8 +8,7 @@
 #include <folly/portability/GTest.h>
 #include <quic/codec/QuicConnectionId.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 TEST(ServerConnectionIdParamsTest, EqOpTest) {
   ServerConnectionIdParams first(1, 5, 7);
   ServerConnectionIdParams second(1, 7, 5);
@@ -17,5 +16,4 @@ TEST(ServerConnectionIdParamsTest, EqOpTest) {
   EXPECT_EQ(first, third);
   EXPECT_NE(first, second);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/codec/test/TypesTest.cpp b/quic/codec/test/TypesTest.cpp
index e27282399..c3aabf067 100644
--- a/quic/codec/test/TypesTest.cpp
+++ b/quic/codec/test/TypesTest.cpp
@@ -17,8 +17,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 std::pair<uint8_t, Buf> encodeShortHeader(const ShortHeader& header) {
   ShortHeader headerCopy = header;
@@ -291,5 +290,4 @@ TEST_F(PacketHeaderTest, ShortHeader) {
 
   EXPECT_EQ(readHeader.asShort()->getConnectionId(), connid);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/common/test/FunctionLooperTest.cpp b/quic/common/test/FunctionLooperTest.cpp
index fbd9c122e..8aea0e74b 100644
--- a/quic/common/test/FunctionLooperTest.cpp
+++ b/quic/common/test/FunctionLooperTest.cpp
@@ -15,8 +15,7 @@ using namespace std;
 using namespace folly;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class FunctionLooperTest : public Test {};
 
@@ -286,5 +285,4 @@ TEST(FunctionLooperTest, NoLoopCallbackInPacingMode) {
   looper->stop();
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/common/test/TestUtils.cpp b/quic/common/test/TestUtils.cpp
index 079ae51c9..1d5c88cb8 100644
--- a/quic/common/test/TestUtils.cpp
+++ b/quic/common/test/TestUtils.cpp
@@ -25,8 +25,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 std::function<MockClock::time_point()> MockClock::mockNow;
 
@@ -842,5 +841,4 @@ Buf copyChain(Buf&& input) {
   return headCopy;
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/common/test/TestUtils.h b/quic/common/test/TestUtils.h
index a14e7928b..f46721217 100644
--- a/quic/common/test/TestUtils.h
+++ b/quic/common/test/TestUtils.h
@@ -28,8 +28,7 @@
 
 #include <quic/codec/QuicConnectionId.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockClock {
  public:
@@ -584,5 +583,4 @@ size_t getTotalIovecLen(const struct iovec* vec, size_t iovec_len);
 
 Buf copyChain(Buf&& input);
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/common/test/TimeUtilTest.cpp b/quic/common/test/TimeUtilTest.cpp
index 75e563489..f9e07efcd 100644
--- a/quic/common/test/TimeUtilTest.cpp
+++ b/quic/common/test/TimeUtilTest.cpp
@@ -9,8 +9,7 @@
 
 #include <gtest/gtest.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 using namespace quic;
 
@@ -41,5 +40,4 @@ TEST(TimeUtil, TestMaxFive) {
   std::chrono::milliseconds ms4 = 10ms;
   EXPECT_EQ(timeMax(ms1, ms2, ms3, ms4).count(), 40);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/common/test/TransportKnobsTest.cpp b/quic/common/test/TransportKnobsTest.cpp
index b7ed3cd9d..41ceff2ad 100644
--- a/quic/common/test/TransportKnobsTest.cpp
+++ b/quic/common/test/TransportKnobsTest.cpp
@@ -11,8 +11,7 @@
 #include <folly/Format.h>
 #include <folly/portability/GTest.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct QuicKnobsParsingTestFixture {
   std::string serializedKnobs;
@@ -246,5 +245,4 @@ TEST(QuicKnobsParsingTest, UInt64Max) {
   run(fixture);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/BandwidthTest.cpp b/quic/congestion_control/test/BandwidthTest.cpp
index 798acd1ab..4dbab6355 100644
--- a/quic/congestion_control/test/BandwidthTest.cpp
+++ b/quic/congestion_control/test/BandwidthTest.cpp
@@ -11,8 +11,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class BandwidthTest : public Test {};
 
@@ -96,5 +95,4 @@ TEST_F(BandwidthTest, Addition) {
   EXPECT_EQ(Bandwidth(45000000, 1s), first);
   EXPECT_TRUE(first.isAppLimited);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/BbrBandwidthSamplerTest.cpp b/quic/congestion_control/test/BbrBandwidthSamplerTest.cpp
index 83ab08f65..89a95f2e4 100644
--- a/quic/congestion_control/test/BbrBandwidthSamplerTest.cpp
+++ b/quic/congestion_control/test/BbrBandwidthSamplerTest.cpp
@@ -13,8 +13,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class BbrBandwidthSamplerTest : public Test {
  protected:
@@ -312,5 +311,4 @@ TEST_F(BbrBandwidthSamplerTest, AppLimitedOutstandingPacket) {
   sampler.onPacketAcked(ackEvent2, 0);
   EXPECT_EQ(bandwidth, sampler.getBandwidth());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/BbrRttSamplerTest.cpp b/quic/congestion_control/test/BbrRttSamplerTest.cpp
index 98d30cbbd..5d4839736 100644
--- a/quic/congestion_control/test/BbrRttSamplerTest.cpp
+++ b/quic/congestion_control/test/BbrRttSamplerTest.cpp
@@ -12,8 +12,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class BbrMinRttSamplerTest : public Test {};
 
@@ -42,5 +41,4 @@ TEST_F(BbrMinRttSamplerTest, NewSampleAndExpiration) {
   EXPECT_TRUE(sampler.minRttExpired());
   EXPECT_EQ(100us, sampler.minRtt());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/BbrTest.cpp b/quic/congestion_control/test/BbrTest.cpp
index 2b1864cd2..cc06c7db3 100644
--- a/quic/congestion_control/test/BbrTest.cpp
+++ b/quic/congestion_control/test/BbrTest.cpp
@@ -16,8 +16,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class BbrTest : public Test {};
 
@@ -833,5 +832,4 @@ TEST_F(BbrTest, GetBandwidthSample) {
   EXPECT_EQ(testBandwidth, bbr.getBandwidth().value());
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CongestionControlFunctionsTest.cpp b/quic/congestion_control/test/CongestionControlFunctionsTest.cpp
index 98804933c..9e99d969b 100644
--- a/quic/congestion_control/test/CongestionControlFunctionsTest.cpp
+++ b/quic/congestion_control/test/CongestionControlFunctionsTest.cpp
@@ -13,8 +13,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class CongestionControlFunctionsTest : public Test {};
 
@@ -71,5 +70,4 @@ TEST_F(CongestionControlFunctionsTest, RttSmallerThanInterval) {
       conn.transportSettings.writeConnectionDataPacketsLimit, result.burstSize);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CopaTest.cpp b/quic/congestion_control/test/CopaTest.cpp
index fbf5921d9..9149fd369 100644
--- a/quic/congestion_control/test/CopaTest.cpp
+++ b/quic/congestion_control/test/CopaTest.cpp
@@ -14,8 +14,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 // TODO: Add UT for different latency factor values
 class CopaTest : public Test {
@@ -567,5 +566,4 @@ TEST_F(CopaTest, PacketLossInvokesPacer) {
   copa.onPacketAckOrLoss(none, lossEvent);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CubicHystartTest.cpp b/quic/congestion_control/test/CubicHystartTest.cpp
index a26b5110b..57b9f55de 100644
--- a/quic/congestion_control/test/CubicHystartTest.cpp
+++ b/quic/congestion_control/test/CubicHystartTest.cpp
@@ -11,8 +11,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class CubicHystartTest : public Test {};
 
@@ -307,5 +306,4 @@ TEST_F(CubicHystartTest, ReduceByCubicReductionFactor) {
   EXPECT_EQ(initCwnd * kDefaultCubicReductionFactor, cubic.getWritableBytes());
   EXPECT_EQ(CubicStates::FastRecovery, cubic.state());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CubicRecoveryTest.cpp b/quic/congestion_control/test/CubicRecoveryTest.cpp
index d3b03d735..7af66b7cf 100644
--- a/quic/congestion_control/test/CubicRecoveryTest.cpp
+++ b/quic/congestion_control/test/CubicRecoveryTest.cpp
@@ -11,8 +11,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class CubicRecoveryTest : public Test {};
 
@@ -165,5 +164,4 @@ TEST_F(CubicRecoveryTest, AckNotLargestNotChangeCwnd) {
   // Cwnd never changed during the whole time, and inflight is 0 at this point:
   EXPECT_EQ(cwndAfterLoss, cubic.getWritableBytes());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CubicStateTest.cpp b/quic/congestion_control/test/CubicStateTest.cpp
index 722e36074..0399d4a40 100644
--- a/quic/congestion_control/test/CubicStateTest.cpp
+++ b/quic/congestion_control/test/CubicStateTest.cpp
@@ -11,8 +11,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class CubicStateTest : public Test {};
 
@@ -107,5 +106,4 @@ TEST_F(CubicStateTest, SteadyLoss) {
   cubic.onPacketAckOrLoss(none, lossEvent);
   EXPECT_EQ(CubicStates::FastRecovery, cubic.state());
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/CubicTest.cpp b/quic/congestion_control/test/CubicTest.cpp
index 5c961cb7e..002bcaff8 100644
--- a/quic/congestion_control/test/CubicTest.cpp
+++ b/quic/congestion_control/test/CubicTest.cpp
@@ -12,8 +12,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class CubicTest : public Test {};
 
@@ -319,5 +318,4 @@ TEST_F(CubicTest, InitCwnd) {
   EXPECT_EQ(cubic.getWritableBytes(), 123456);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/Mocks.h b/quic/congestion_control/test/Mocks.h
index 305de1509..1b1271f37 100644
--- a/quic/congestion_control/test/Mocks.h
+++ b/quic/congestion_control/test/Mocks.h
@@ -8,8 +8,7 @@
 #include <folly/portability/GMock.h>
 #include <quic/congestion_control/Bbr.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockMinRttSampler : public BbrCongestionController::MinRttSampler {
  public:
@@ -41,5 +40,4 @@ class MockBandwidthSampler : public BbrCongestionController::BandwidthSampler {
   MOCK_METHOD(void, setWindowLength, (const uint64_t), (noexcept));
 };
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/NewRenoTest.cpp b/quic/congestion_control/test/NewRenoTest.cpp
index fad24438e..7acea01c4 100644
--- a/quic/congestion_control/test/NewRenoTest.cpp
+++ b/quic/congestion_control/test/NewRenoTest.cpp
@@ -13,8 +13,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class NewRenoTest : public Test {};
 
@@ -259,5 +258,4 @@ TEST_F(NewRenoTest, RemoveBytesWithoutLossOrAck) {
   reno.onRemoveBytesFromInflight(2);
   EXPECT_EQ(reno.getWritableBytes(), originalWritableBytes - ackedSize + 2);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/PacerTest.cpp b/quic/congestion_control/test/PacerTest.cpp
index 1163ba4cb..fa62014d1 100644
--- a/quic/congestion_control/test/PacerTest.cpp
+++ b/quic/congestion_control/test/PacerTest.cpp
@@ -14,8 +14,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class TokenlessPacerTest : public Test {
  public:
@@ -280,5 +279,4 @@ TEST_F(TokenlessPacerTest, RefreshPacingRateWhenRTTIsDefault) {
   EXPECT_EQ(tick, pacer.getTimeUntilNextWrite(timestamp));
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/congestion_control/test/TestingCubic.h b/quic/congestion_control/test/TestingCubic.h
index a7fa7d3f2..94bb0199f 100644
--- a/quic/congestion_control/test/TestingCubic.h
+++ b/quic/congestion_control/test/TestingCubic.h
@@ -7,8 +7,7 @@
 
 #include <quic/congestion_control/QuicCubic.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class TestingCubic : public Cubic {
  public:
@@ -25,5 +24,4 @@ class TestingCubic : public Cubic {
   }
 };
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/dsr/backend/test/DSRPacketizerTest.cpp b/quic/dsr/backend/test/DSRPacketizerTest.cpp
index 8f6aa0807..e6801e4ac 100644
--- a/quic/dsr/backend/test/DSRPacketizerTest.cpp
+++ b/quic/dsr/backend/test/DSRPacketizerTest.cpp
@@ -27,8 +27,7 @@ fizz::TrafficKey getFizzTestKey() {
 }
 } // namespace
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class DSRPacketizerTest : public DSRCommonTestFixture {};
 
@@ -215,5 +214,4 @@ TEST_F(DSRMultiWriteTest, TwoRequestsWithLoss) {
   EXPECT_GT(sentData[1]->computeChainDataLength(), 500);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/dsr/frontend/test/PacketBuilderTest.cpp b/quic/dsr/frontend/test/PacketBuilderTest.cpp
index 8d7decf34..a49b97d5b 100644
--- a/quic/dsr/frontend/test/PacketBuilderTest.cpp
+++ b/quic/dsr/frontend/test/PacketBuilderTest.cpp
@@ -14,8 +14,7 @@
 #include <quic/handshake/test/Mocks.h>
 #include <quic/server/state/ServerStateMachine.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 bool operator==(
     const SendInstruction& instruction,
@@ -112,5 +111,4 @@ TEST_F(PacketBuilderTest, WriteTwoInstructions) {
   EXPECT_TRUE(expectedSecondFrame == packet.sendInstructions[1]);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/dsr/frontend/test/SchedulerTest.cpp b/quic/dsr/frontend/test/SchedulerTest.cpp
index 3a81c2b2b..9aceeac10 100644
--- a/quic/dsr/frontend/test/SchedulerTest.cpp
+++ b/quic/dsr/frontend/test/SchedulerTest.cpp
@@ -15,8 +15,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class SchedulerTest : public DSRCommonTestFixture {
  public:
@@ -95,5 +94,4 @@ TEST_F(SchedulerTest, ScheduleStream) {
   EXPECT_TRUE(conn_.streamManager->writableDSRStreams().empty());
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/dsr/frontend/test/WriteCodecTest.cpp b/quic/dsr/frontend/test/WriteCodecTest.cpp
index 6bd7364a0..4dffb7e5f 100644
--- a/quic/dsr/frontend/test/WriteCodecTest.cpp
+++ b/quic/dsr/frontend/test/WriteCodecTest.cpp
@@ -18,8 +18,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class WriteCodecTest : public DSRCommonTestFixture {
  public:
@@ -306,5 +305,4 @@ TEST_F(WriteCodecTest, NoFINNoData) {
           bufMetaStartingOffset),
       QuicInternalException);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/client/handshake/test/FizzClientExtensionsTest.cpp b/quic/fizz/client/handshake/test/FizzClientExtensionsTest.cpp
index a4160b8bb..37251dd88 100644
--- a/quic/fizz/client/handshake/test/FizzClientExtensionsTest.cpp
+++ b/quic/fizz/client/handshake/test/FizzClientExtensionsTest.cpp
@@ -15,8 +15,7 @@
 using namespace fizz;
 using namespace fizz::test;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 static EncryptedExtensions getEncryptedExtensions() {
   auto ee = TestMessages::encryptedExt();
@@ -204,5 +203,4 @@ TEST(FizzClientHandshakeTest, TestGetChloExtensionsCustomParams) {
   auto val = decodeQuicInteger(cursor1);
   EXPECT_EQ(val->first, 12);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/client/handshake/test/FizzClientHandshakeTest.cpp b/quic/fizz/client/handshake/test/FizzClientHandshakeTest.cpp
index 929a325cf..03890e5c6 100644
--- a/quic/fizz/client/handshake/test/FizzClientHandshakeTest.cpp
+++ b/quic/fizz/client/handshake/test/FizzClientHandshakeTest.cpp
@@ -38,8 +38,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class ClientHandshakeTest : public Test, public boost::static_visitor<> {
  public:
@@ -714,5 +713,4 @@ TEST_F(ClientHandshakeECHPolicyTest, TestECHPolicyHandshake) {
   EXPECT_NE(handshakeBytes.find("public.dummy.com"), handshakeBytes.size());
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/client/test/QuicClientTransportTest.cpp b/quic/fizz/client/test/QuicClientTransportTest.cpp
index 88be7cdd5..9fe578c75 100644
--- a/quic/fizz/client/test/QuicClientTransportTest.cpp
+++ b/quic/fizz/client/test/QuicClientTransportTest.cpp
@@ -35,8 +35,7 @@ using namespace testing;
 using namespace folly;
 using namespace quic::samples;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 namespace {
 std::vector<uint8_t> kInitialDstConnIdVecForRetryTest =
@@ -5940,5 +5939,4 @@ TEST(AsyncUDPSocketTest, CloseMultipleTimes) {
   socket.pauseRead();
   socket.close();
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/handshake/test/FizzCryptoFactoryTest.cpp b/quic/fizz/handshake/test/FizzCryptoFactoryTest.cpp
index 5530d09b9..9722e718c 100644
--- a/quic/fizz/handshake/test/FizzCryptoFactoryTest.cpp
+++ b/quic/fizz/handshake/test/FizzCryptoFactoryTest.cpp
@@ -15,8 +15,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicFizzTestFactory : public QuicFizzFactory {
  public:
@@ -114,5 +113,4 @@ TEST_F(FizzCryptoFactoryTest, TestPacketEncryptionKey) {
   EXPECT_EQ(secretHex2, expectedKey2);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/handshake/test/FizzPacketNumberCipherTest.cpp b/quic/fizz/handshake/test/FizzPacketNumberCipherTest.cpp
index f84a9ae85..7972e259a 100644
--- a/quic/fizz/handshake/test/FizzPacketNumberCipherTest.cpp
+++ b/quic/fizz/handshake/test/FizzPacketNumberCipherTest.cpp
@@ -15,8 +15,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct HeaderParams {
   fizz::CipherSuite cipher;
@@ -128,5 +127,4 @@ INSTANTIATE_TEST_SUITE_P(
             folly::StringPiece{"772aa701"},
             folly::StringPiece{"ce"}}));
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/handshake/test/FizzTransportParametersTest.cpp b/quic/fizz/handshake/test/FizzTransportParametersTest.cpp
index da80b56ef..1e1465a70 100644
--- a/quic/fizz/handshake/test/FizzTransportParametersTest.cpp
+++ b/quic/fizz/handshake/test/FizzTransportParametersTest.cpp
@@ -15,8 +15,7 @@
 using namespace fizz;
 using namespace folly;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicExtensionsTest : public testing::Test {
  protected:
@@ -173,5 +172,4 @@ TEST_F(QuicExtensionsTest, TestTicketParamsD29) {
   checkEncode(std::move(*ext), ticketParamsD29, kQuicDraft);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/fizz/server/handshake/AppToken.h b/quic/fizz/server/handshake/AppToken.h
index 87e6927ea..878996c64 100644
--- a/quic/fizz/server/handshake/AppToken.h
+++ b/quic/fizz/server/handshake/AppToken.h
@@ -21,8 +21,7 @@ Optional<AppToken> decodeAppToken(const folly::IOBuf& buf);
 
 } // namespace quic
 
-namespace fizz {
-namespace detail {
+namespace fizz::detail {
 
 template <>
 struct Reader<folly::IPAddress> {
@@ -54,5 +53,4 @@ struct Sizer<folly::IPAddress> {
   }
 };
 
-} // namespace detail
-} // namespace fizz
+} // namespace fizz::detail
diff --git a/quic/fizz/server/handshake/FizzServerHandshake.cpp b/quic/fizz/server/handshake/FizzServerHandshake.cpp
index c2b7a0d77..4fa8f53b3 100644
--- a/quic/fizz/server/handshake/FizzServerHandshake.cpp
+++ b/quic/fizz/server/handshake/FizzServerHandshake.cpp
@@ -19,11 +19,9 @@
 // QuicServerConnectionState.
 #include <quic/server/state/ServerStateMachine.h>
 
-namespace fizz {
-namespace server {
+namespace fizz::server {
 struct ResumptionState;
-} // namespace server
-} // namespace fizz
+} // namespace fizz::server
 
 namespace {
 class FailingAppTokenValidator : public fizz::server::AppTokenValidator {
diff --git a/quic/flowcontrol/test/QuicFlowControlTest.cpp b/quic/flowcontrol/test/QuicFlowControlTest.cpp
index bdcb022bf..a3fc6a370 100644
--- a/quic/flowcontrol/test/QuicFlowControlTest.cpp
+++ b/quic/flowcontrol/test/QuicFlowControlTest.cpp
@@ -16,8 +16,7 @@
 using namespace folly;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicFlowControlTest : public Test {
  public:
@@ -991,5 +990,4 @@ TEST_F(QuicFlowControlTest, StreamFlowControlWithBufMeta) {
   EXPECT_EQ(400, getSendStreamFlowControlBytesAPI(stream));
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/handshake/test/Mocks.h b/quic/handshake/test/Mocks.h
index 534e6251b..c173e47a0 100644
--- a/quic/handshake/test/Mocks.h
+++ b/quic/handshake/test/Mocks.h
@@ -13,8 +13,7 @@
 #include <quic/handshake/Aead.h>
 #include <quic/handshake/HandshakeLayer.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 // Forward declaration
 std::array<uint8_t, kStatelessResetTokenSecretLength> getRandSecret();
@@ -100,5 +99,4 @@ class MockAead : public Aead {
   }
 };
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/loss/test/QuicLossFunctionsTest.cpp b/quic/loss/test/QuicLossFunctionsTest.cpp
index 435f16127..7906a2e74 100644
--- a/quic/loss/test/QuicLossFunctionsTest.cpp
+++ b/quic/loss/test/QuicLossFunctionsTest.cpp
@@ -63,8 +63,7 @@ auto getOutstandingPacketMatcher(
 }
 } // namespace
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockLossTimeout {
  public:
@@ -3454,5 +3453,4 @@ TEST_F(
   EXPECT_EQ(stream2->lossBuffer.size(), 1);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/samples/echo/EchoClient.h b/quic/samples/echo/EchoClient.h
index ed9a40a9d..49c4b2a40 100644
--- a/quic/samples/echo/EchoClient.h
+++ b/quic/samples/echo/EchoClient.h
@@ -31,8 +31,7 @@
 #include <quic/fizz/client/handshake/FizzClientQuicHandshakeContext.h>
 #include <quic/samples/echo/LogQuicStats.h>
 
-namespace quic {
-namespace samples {
+namespace quic::samples {
 
 constexpr size_t kNumTestStreamGroups = 2;
 
@@ -387,5 +386,4 @@ class EchoClient : public quic::QuicSocket::ConnectionSetupCallback,
   std::string clientCertPath_;
   std::string clientKeyPath_;
 };
-} // namespace samples
-} // namespace quic
+} // namespace quic::samples
diff --git a/quic/samples/echo/EchoHandler.h b/quic/samples/echo/EchoHandler.h
index 9f2bb6f87..0427923a4 100644
--- a/quic/samples/echo/EchoHandler.h
+++ b/quic/samples/echo/EchoHandler.h
@@ -11,8 +11,7 @@
 
 #include <quic/common/BufUtil.h>
 
-namespace quic {
-namespace samples {
+namespace quic::samples {
 class EchoHandler : public quic::QuicSocket::ConnectionSetupCallback,
                     public quic::QuicSocket::ConnectionCallback,
                     public quic::QuicSocket::ReadCallback,
@@ -242,5 +241,4 @@ class EchoHandler : public quic::QuicSocket::ConnectionSetupCallback,
   std::map<quic::StreamGroupId, PerStreamData> streamGroupsData_;
   bool disableRtx_{false};
 };
-} // namespace samples
-} // namespace quic
+} // namespace quic::samples
diff --git a/quic/samples/echo/EchoServer.h b/quic/samples/echo/EchoServer.h
index 4eaa05386..c75530848 100644
--- a/quic/samples/echo/EchoServer.h
+++ b/quic/samples/echo/EchoServer.h
@@ -17,8 +17,7 @@
 #include <quic/server/QuicServerTransport.h>
 #include <quic/server/QuicSharedUDPSocketFactory.h>
 
-namespace quic {
-namespace samples {
+namespace quic::samples {
 
 class EchoServerTransportFactory : public quic::QuicServerTransportFactory {
  public:
@@ -129,5 +128,4 @@ class EchoServer {
   std::shared_ptr<quic::QuicServer> server_;
   std::vector<std::string> alpns_;
 };
-} // namespace samples
-} // namespace quic
+} // namespace quic::samples
diff --git a/quic/samples/echo/LogQuicStats.h b/quic/samples/echo/LogQuicStats.h
index e94d4865e..18f6c824e 100644
--- a/quic/samples/echo/LogQuicStats.h
+++ b/quic/samples/echo/LogQuicStats.h
@@ -13,8 +13,7 @@
 #include <quic/codec/Types.h>
 #include <quic/state/QuicTransportStatsCallback.h>
 
-namespace quic {
-namespace samples {
+namespace quic::samples {
 class LogQuicStats : public quic::QuicTransportStatsCallback {
  public:
   explicit LogQuicStats(const std::string& prefix) : prefix_(prefix + " ") {}
@@ -293,5 +292,4 @@ class LogQuicStatsFactory : public QuicTransportStatsCallbackFactory {
   }
 };
 
-} // namespace samples
-} // namespace quic
+} // namespace quic::samples
diff --git a/quic/server/handshake/DefaultAppTokenValidator.h b/quic/server/handshake/DefaultAppTokenValidator.h
index a33f4b6d5..c50cf58a6 100644
--- a/quic/server/handshake/DefaultAppTokenValidator.h
+++ b/quic/server/handshake/DefaultAppTokenValidator.h
@@ -16,11 +16,9 @@
 #include <memory>
 #include <string>
 
-namespace fizz {
-namespace server {
+namespace fizz::server {
 struct ResumptionState;
-} // namespace server
-} // namespace fizz
+} // namespace fizz::server
 
 namespace quic {
 struct QuicServerConnectionState;
diff --git a/quic/server/handshake/test/AppTokenTest.cpp b/quic/server/handshake/test/AppTokenTest.cpp
index fa4390dce..cd18901ab 100644
--- a/quic/server/handshake/test/AppTokenTest.cpp
+++ b/quic/server/handshake/test/AppTokenTest.cpp
@@ -17,8 +17,7 @@
 
 #include <cstdint>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 void expectAppTokenEqual(
     const Optional<AppToken>& decodedAppToken,
@@ -273,5 +272,4 @@ TEST(AppTokenTest, TestEncodeAndDecodeCwndHint) {
   expectAppTokenEqual(decodeAppToken(*buf), appToken);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/handshake/test/DefaultAppTokenValidatorTest.cpp b/quic/server/handshake/test/DefaultAppTokenValidatorTest.cpp
index 29aee0174..504eac648 100644
--- a/quic/server/handshake/test/DefaultAppTokenValidatorTest.cpp
+++ b/quic/server/handshake/test/DefaultAppTokenValidatorTest.cpp
@@ -23,8 +23,7 @@
 using namespace fizz::server;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 TEST(DefaultAppTokenValidatorTest, TestValidParams) {
   QuicServerConnectionState conn(
@@ -646,5 +645,4 @@ TEST_F(AlwaysRejectPolicyTest, MaxNumSourceTokenAddrMatch) {
   EXPECT_TRUE(conn_.isClientAddrVerified);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/handshake/test/ServerHandshakeTest.cpp b/quic/server/handshake/test/ServerHandshakeTest.cpp
index bfdd12297..1da26e02c 100644
--- a/quic/server/handshake/test/ServerHandshakeTest.cpp
+++ b/quic/server/handshake/test/ServerHandshakeTest.cpp
@@ -39,8 +39,7 @@ using namespace testing;
 
 static constexpr folly::StringPiece kTestHostname = "www.facebook.com";
 
-namespace quic {
-namespace test {
+namespace quic::test {
 class MockServerHandshakeCallback : public ServerHandshake::HandshakeCallback {
  public:
   ~MockServerHandshakeCallback() override = default;
@@ -883,5 +882,4 @@ TEST_F(ServerHandshakeZeroRttTest, TestRejectZeroRttInvalidToken) {
   EXPECT_EQ(handshake->getPhase(), ServerHandshake::Phase::Established);
   expectOneRttCipher(true);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/handshake/test/ServerTransportParametersTest.cpp b/quic/server/handshake/test/ServerTransportParametersTest.cpp
index 7a73b5cae..d560b0123 100644
--- a/quic/server/handshake/test/ServerTransportParametersTest.cpp
+++ b/quic/server/handshake/test/ServerTransportParametersTest.cpp
@@ -19,8 +19,7 @@
 using namespace fizz;
 using namespace fizz::test;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 static ClientHello getClientHello(QuicVersion version) {
   auto chlo = TestMessages::clientHello();
@@ -202,5 +201,4 @@ TEST(ServerTransportParametersTest, TestMvfstFields) {
   EXPECT_FALSE(hasOriginalDestCid);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/handshake/test/StatelessResetGeneratorTest.cpp b/quic/server/handshake/test/StatelessResetGeneratorTest.cpp
index 002cd7dbd..ca74ece40 100644
--- a/quic/server/handshake/test/StatelessResetGeneratorTest.cpp
+++ b/quic/server/handshake/test/StatelessResetGeneratorTest.cpp
@@ -13,8 +13,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class StatelessResetGeneratorTest : public Test {};
 
@@ -55,5 +54,4 @@ TEST_F(StatelessResetGeneratorTest, DifferentSecretSameAddress) {
       generator2.generateToken(ConnectionId({0x14, 0x35, 0x22, 0x11})));
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/test/QuicServerTest.cpp b/quic/server/test/QuicServerTest.cpp
index e3668ab80..f68ba86af 100644
--- a/quic/server/test/QuicServerTest.cpp
+++ b/quic/server/test/QuicServerTest.cpp
@@ -43,8 +43,7 @@ const folly::SocketAddress kClientAddr("1.2.3.4", 1234);
 const folly::SocketAddress kClientAddr2("1.2.3.5", 1235);
 const folly::SocketAddress kClientAddr3("1.2.3.6", 1236);
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 MATCHER_P(NetworkDataMatches, networkData, "") {
   for (size_t i = 0; i < arg.getPackets().size(); ++i) {
@@ -3232,5 +3231,4 @@ TEST_F(QuicServerTest, OneEVB) {
   evb.loop();
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/server/test/QuicServerTransportTest.cpp b/quic/server/test/QuicServerTransportTest.cpp
index 33eafabc1..f77a33de7 100644
--- a/quic/server/test/QuicServerTransportTest.cpp
+++ b/quic/server/test/QuicServerTransportTest.cpp
@@ -21,8 +21,7 @@
 using namespace testing;
 using namespace folly;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 namespace {
 using ByteEvent = QuicTransportBase::ByteEvent;
@@ -5656,5 +5655,4 @@ TEST_F(QuicServerTransportCertTest, TestGetSelfCertificate) {
   conn.serverHandshakeLayer = serverHandshakeLayer;
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/stream/test/StreamStateFunctionsTest.cpp b/quic/state/stream/test/StreamStateFunctionsTest.cpp
index 6083e2d5b..dfda8efcc 100644
--- a/quic/state/stream/test/StreamStateFunctionsTest.cpp
+++ b/quic/state/stream/test/StreamStateFunctionsTest.cpp
@@ -19,8 +19,7 @@
 
 using namespace ::testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class StreamStateFunctionsTests : public Test {};
 
@@ -346,5 +345,4 @@ TEST_F(StreamStateFunctionsTests, ResetAfterReadingAllBytesTillFin) {
   EXPECT_FALSE(conn.streamManager->hasWindowUpdates());
   EXPECT_FALSE(conn.pendingEvents.connWindowUpdate);
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/stream/test/StreamStateMachineTest.cpp b/quic/state/stream/test/StreamStateMachineTest.cpp
index f0f994fa6..c90314e9d 100644
--- a/quic/state/stream/test/StreamStateMachineTest.cpp
+++ b/quic/state/stream/test/StreamStateMachineTest.cpp
@@ -20,8 +20,7 @@
 using namespace folly;
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 void verifyStreamReset(
     const QuicStreamState& stream,
@@ -900,5 +899,4 @@ TEST_F(QuicOpenStateTest, DSRFullStreamAcked) {
   EXPECT_EQ(stream->sendState, StreamSendState::Closed);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/AckHandlersTest.cpp b/quic/state/test/AckHandlersTest.cpp
index 9688afcbb..c79649cd9 100644
--- a/quic/state/test/AckHandlersTest.cpp
+++ b/quic/state/test/AckHandlersTest.cpp
@@ -27,8 +27,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct AckHandlersTestParam {
   PacketNumberSpace pnSpace;
@@ -7342,5 +7341,4 @@ INSTANTIATE_TEST_SUITE_P(
         AckHandlersTestParam{
             PacketNumberSpace::AppData,
             FrameType::ACK_RECEIVE_TIMESTAMPS}));
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/AckedPacketIteratorTest.cpp b/quic/state/test/AckedPacketIteratorTest.cpp
index 8cfa840d9..e9e566a37 100644
--- a/quic/state/test/AckedPacketIteratorTest.cpp
+++ b/quic/state/test/AckedPacketIteratorTest.cpp
@@ -13,8 +13,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class AckedPacketIteratorTest : public virtual testing::Test {
  public:
@@ -396,5 +395,4 @@ TEST_F(AckedPacketIteratorTest, ErasureTwoOpIntervals) {
   EXPECT_THAT(expectedOutstandings, ContainerEq(getOutstandings()));
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/ClonedPacketIdentifierTest.cpp b/quic/state/test/ClonedPacketIdentifierTest.cpp
index 438aac07b..82f26f10f 100644
--- a/quic/state/test/ClonedPacketIdentifierTest.cpp
+++ b/quic/state/test/ClonedPacketIdentifierTest.cpp
@@ -9,8 +9,7 @@
 
 #include <folly/portability/GTest.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 TEST(ClonedPacketIdentifierTest, EqTest) {
   ClonedPacketIdentifier initialClonedPacketIdentifier(
       PacketNumberSpace::Initial, 0);
@@ -45,5 +44,4 @@ TEST(ClonedPacketIdentifierTest, HashTest) {
       hashObj(initialClonedPacketIdentifier0),
       hashObj(handshakeClonedPacketIdentifier0));
 }
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/Mocks.h b/quic/state/test/Mocks.h
index 5847ad37a..e089984c7 100644
--- a/quic/state/test/Mocks.h
+++ b/quic/state/test/Mocks.h
@@ -12,8 +12,7 @@
 #include <quic/congestion_control/CongestionControllerFactory.h>
 #include <quic/state/StateData.h>
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class MockCongestionControllerFactory : public CongestionControllerFactory {
  public:
@@ -117,5 +116,4 @@ class MockQuicStreamPrioritiesObserver : public QuicStreamPrioritiesObserver {
  public:
   MOCK_METHOD(void, onStreamPrioritiesChange, ());
 };
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/QuicPacingFunctionsTest.cpp b/quic/state/test/QuicPacingFunctionsTest.cpp
index b506a9712..caca5d875 100644
--- a/quic/state/test/QuicPacingFunctionsTest.cpp
+++ b/quic/state/test/QuicPacingFunctionsTest.cpp
@@ -11,8 +11,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class QuicPacingFunctionsTest : public Test {};
 
@@ -30,5 +29,4 @@ TEST_F(QuicPacingFunctionsTest, OnClose) {
   EXPECT_FALSE(conn.canBePaced);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/QuicStreamManagerTest.cpp b/quic/state/test/QuicStreamManagerTest.cpp
index 918c270e1..ad3a4d08f 100644
--- a/quic/state/test/QuicStreamManagerTest.cpp
+++ b/quic/state/test/QuicStreamManagerTest.cpp
@@ -18,8 +18,7 @@
 
 using namespace testing;
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 struct StreamManagerTestParam {
   bool notifyOnNewStreamsExplicitly{false};
@@ -1000,5 +999,4 @@ INSTANTIATE_TEST_SUITE_P(
         StreamManagerTestParam{true, false},
         StreamManagerTestParam{true, true}));
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/state/test/StateDataTest.cpp b/quic/state/test/StateDataTest.cpp
index c0fdee57c..eff51467d 100644
--- a/quic/state/test/StateDataTest.cpp
+++ b/quic/state/test/StateDataTest.cpp
@@ -18,8 +18,7 @@ using namespace testing;
 
 constexpr QuicVersion kVersion = static_cast<QuicVersion>(0);
 
-namespace quic {
-namespace test {
+namespace quic::test {
 
 class StateDataTest : public Test {};
 
@@ -303,5 +302,4 @@ TEST_F(
       maxWindowBytes);
 }
 
-} // namespace test
-} // namespace quic
+} // namespace quic::test
diff --git a/quic/tools/tperf/TperfQLogger.cpp b/quic/tools/tperf/TperfQLogger.cpp
index 1065844d4..94fac9816 100644
--- a/quic/tools/tperf/TperfQLogger.cpp
+++ b/quic/tools/tperf/TperfQLogger.cpp
@@ -7,8 +7,7 @@
 
 #include <quic/tools/tperf/TperfQLogger.h>
 
-namespace quic {
-namespace tperf {
+namespace quic::tperf {
 
 TperfQLogger::TperfQLogger(VantagePoint vantagePoint, const std::string& path)
     : FileQLogger(
@@ -57,5 +56,4 @@ void TperfQLogger::addPacingMetricUpdate(
   }
   FileQLogger::addPacingMetricUpdate(pacingBurstSize, pacingInterval);
 }
-} // namespace tperf
-} // namespace quic
+} // namespace quic::tperf
diff --git a/quic/tools/tperf/TperfQLogger.h b/quic/tools/tperf/TperfQLogger.h
index b5f0e8923..692c3e971 100644
--- a/quic/tools/tperf/TperfQLogger.h
+++ b/quic/tools/tperf/TperfQLogger.h
@@ -10,8 +10,7 @@
 #include <quic/logging/FileQLogger.h>
 #include <quic/tools/tperf/PacingObserver.h>
 
-namespace quic {
-namespace tperf {
+namespace quic::tperf {
 class TperfQLogger : public FileQLogger {
  public:
   explicit TperfQLogger(VantagePoint vantagePoint, const std::string& path);
@@ -38,5 +37,4 @@ class TperfQLogger : public FileQLogger {
   std::string path_;
   std::unique_ptr<PacingObserver> pacingObserver_;
 };
-} // namespace tperf
-} // namespace quic
+} // namespace quic::tperf
diff --git a/quic/tools/tperf/tperf.cpp b/quic/tools/tperf/tperf.cpp
index 0ae3f0cd1..d53bcfd25 100644
--- a/quic/tools/tperf/tperf.cpp
+++ b/quic/tools/tperf/tperf.cpp
@@ -109,8 +109,7 @@ DEFINE_bool(
     "Whether to read and echo ecn marking from ingress packets");
 DEFINE_uint32(dscp, 0, "DSCP value to use for outgoing packets");
 
-namespace quic {
-namespace tperf {
+namespace quic::tperf {
 
 namespace {
 
@@ -766,8 +765,7 @@ class TPerfClient : public quic::QuicSocket::ConnectionSetupCallback,
   bool useInplaceWrite_{false};
 };
 
-} // namespace tperf
-} // namespace quic
+} // namespace quic::tperf
 
 using namespace quic::tperf;