diff --git a/tests/testTransport.cpp b/tests/testTransport.cpp
index a890307..1806829 100644
--- a/tests/testTransport.cpp
+++ b/tests/testTransport.cpp
@@ -163,3 +163,161 @@ VF_TEST(reliableMessagesLargerThanTheMtuAreFragmentedAndReassembledByteForByte)
     CHECK(got == huge);
     CHECK_EQ(sender.unackedFragmentCount(), static_cast<std::size_t>(0));
 
+    ByteBuffer extra;
+    CHECK(!receiver.popReliable(extra));
+}
+
+VF_TEST(unreliableChannelDropsAMessageOlderThanTheNewestOneAlreadyDelivered) {
+    LinkQuality slow;
+    slow.latencyTicks = 12;
+    slow.seed = 0x2222333344445555ull;
+    LoopbackLink link(slow);
+
+    TransportConfig config;
+    config.mtu = 256;
+    Transport sender(link, 0, config);
+    Transport receiver(link, 1, config);
+
+    sender.sendUnreliable(messageOf(0, 32));
+    sender.flush(0);
+
+    LinkQuality fast = slow;
+    fast.latencyTicks = 1;
+    link.setQuality(fast);
+
+    sender.sendUnreliable(messageOf(1, 32));
+    sender.flush(1);
+
+    std::vector<uint32_t> received;
+    for (uint64_t tick = 2; tick < 40; ++tick) {
+        receiver.pump(tick);
+        receiver.flush(tick);
+        ByteBuffer got;
+        while (receiver.popUnreliable(got)) received.push_back(indexOf(got));
+    }
+
+    CHECK_EQ(received.size(), static_cast<std::size_t>(1));
+    CHECK_EQ(received[0], 1u);
+    CHECK_EQ(receiver.stats().staleDropped, static_cast<uint64_t>(1));
+    CHECK_EQ(receiver.unreliableChannel().highestDeliveredMessageId(), 1u);
+}
+
+VF_TEST(unreliableMessagesAreNeverRetransmittedWhileReliableOnesAre) {
+    LinkQuality quality;
+    quality.lossPercent = 50;
+    quality.latencyTicks = 1;
+    quality.seed = 0x5a5a5a5a5a5a5a5aull;
+
+    LoopbackLink lossyUnreliable(quality);
+    TransportConfig config;
+    config.mtu = 256;
+    config.retransmitTimeoutTicks = 4;
+    Transport unreliableSender(lossyUnreliable, 0, config);
+    Transport unreliableReceiver(lossyUnreliable, 1, config);
+    for (uint32_t i = 0; i < 40; ++i) unreliableSender.sendUnreliable(messageOf(i, 24));
+
+    std::size_t unreliableArrived = 0;
+    for (uint64_t tick = 0; tick < 200; ++tick) {
+        stepPair(unreliableSender, unreliableReceiver, tick);
+        ByteBuffer got;
+        while (unreliableReceiver.popUnreliable(got)) ++unreliableArrived;
+    }
+    CHECK(unreliableArrived < 40u);
+    CHECK_EQ(unreliableSender.stats().retransmitted, static_cast<uint64_t>(0));
+
+    LoopbackLink lossyReliable(quality);
+    Transport reliableSender(lossyReliable, 0, config);
+    Transport reliableReceiver(lossyReliable, 1, config);
+    for (uint32_t i = 0; i < 40; ++i) reliableSender.sendReliable(messageOf(i, 24));
+
+    std::size_t reliableArrived = 0;
+    for (uint64_t tick = 0; tick < 600; ++tick) {
+        stepPair(reliableSender, reliableReceiver, tick);
+        ByteBuffer got;
+        while (reliableReceiver.popReliable(got)) ++reliableArrived;
+    }
+    CHECK_EQ(reliableArrived, static_cast<std::size_t>(40));
+    CHECK(reliableSender.stats().retransmitted > 0u);
+    CHECK(reliableSender.stats().datagramsLost > 0u);
+}
+
+VF_TEST(duplicatedDatagramsAreCountedAndNeverDeliveredTwice) {
+    LinkQuality quality;
+    quality.duplicatePercent = 100;
+    quality.latencyTicks = 1;
+    quality.seed = 0x0badc0de0badc0deull;
+
+    LoopbackLink link(quality);
+    TransportConfig config;
+    config.mtu = 256;
+    Transport sender(link, 0, config);
+    Transport receiver(link, 1, config);
+
+    for (uint32_t i = 0; i < 30; ++i) sender.sendReliable(messageOf(i, 60));
+
+    std::vector<uint32_t> order;
+    for (uint64_t tick = 0; tick < 200; ++tick) {
+        stepPair(sender, receiver, tick);
+        ByteBuffer got;
+        while (receiver.popReliable(got)) order.push_back(indexOf(got));
+    }
+
+    CHECK_EQ(order.size(), static_cast<std::size_t>(30));
+    for (std::size_t i = 0; i < order.size(); ++i) CHECK_EQ(order[i], static_cast<uint32_t>(i));
+    CHECK(receiver.stats().duplicatesDropped > 0u);
+    CHECK_EQ(link.duplicatedCount(), link.sentCount() - link.droppedCount());
+    CHECK(receiver.stats().datagramsReceived > receiver.stats().duplicatesDropped);
+}
+
+VF_TEST(theSendWindowCapsHowManyDatagramsCanBeUnacknowledgedAtOnce) {
+    LinkQuality quality;
+    quality.latencyTicks = 6;
+    quality.seed = 0x1010101020202020ull;
+
+    LoopbackLink link(quality);
+    TransportConfig config;
+    config.mtu = 96;
+    config.sendWindow = 4;
+    config.retransmitTimeoutTicks = 40;
+    Transport sender(link, 0, config);
+    Transport receiver(link, 1, config);
+
+    for (uint32_t i = 0; i < 60; ++i) sender.sendReliable(messageOf(i, 50));
+
+    std::size_t peakInFlight = 0;
+    std::size_t arrived = 0;
+    for (uint64_t tick = 0; tick < 900; ++tick) {
+        stepPair(sender, receiver, tick);
+        if (sender.inFlightDatagramCount() > peakInFlight)
+            peakInFlight = sender.inFlightDatagramCount();
+        ByteBuffer got;
+        while (receiver.popReliable(got)) ++arrived;
+    }
+    CHECK_EQ(peakInFlight, static_cast<std::size_t>(4));
+    CHECK_EQ(arrived, static_cast<std::size_t>(60));
+}
+
+VF_TEST(smoothedRoundTripTimeConvergesOnTheLinkLatency) {
+    LinkQuality quality;
+    quality.latencyTicks = 3;
+    quality.seed = 0x9999888877776666ull;
+
+    LoopbackLink link(quality);
+    TransportConfig config;
+    config.mtu = 256;
+    config.retransmitTimeoutTicks = 30;
+    Transport sender(link, 0, config);
+    Transport receiver(link, 1, config);
+
+    CHECK_EQ(sender.stats().smoothedRttTicks, 0.0);
+    for (uint32_t i = 0; i < 40; ++i) sender.sendReliable(messageOf(i, 20));
+    for (uint64_t tick = 0; tick < 120; ++tick) {
+        stepPair(sender, receiver, tick);
+        ByteBuffer got;
+        while (receiver.popReliable(got)) {
+        }
+    }
+    CHECK_NEAR(sender.stats().smoothedRttTicks, 6.0, 0.001);
+    CHECK_EQ(sender.stats().datagramsLost, static_cast<uint64_t>(0));
+}
+