diff --git a/tests/testWorldBackup.cpp b/tests/testWorldBackup.cpp
index 24938be..a49945c 100644
--- a/tests/testWorldBackup.cpp
+++ b/tests/testWorldBackup.cpp
@@ -314,3 +314,139 @@ VF_TEST(captureMigratedLiftsAnOldSaveBeforeStoringIt) {
     legacy.chunks.push_back(buildRecord({1, 0, 0}, texturedChunk(2), SaveVersion::V1));
     ByteBuffer ancient = writeSaveContainer(legacy);
 
+    BackupStore store;
+    uint32_t id = store.captureMigrated(BackupKind::Full, ancient, 0);
+    CHECK(id != 0u);
+    const BackupEntry* entry = store.index().find(id);
+    CHECK(entry != nullptr);
+    if (entry == nullptr) return;
+    CHECK(entry->version == currentSaveVersion);
+
+    RestoreResult restored = store.restore(id);
+    CHECK(restored.ok);
+    SaveContainer reloaded;
+    CHECK(readSaveContainer(restored.save.data(), restored.save.size(), reloaded));
+    CHECK(reloaded.version == SaveVersion::V4);
+    for (const SaveChunkRecord& before : legacy.chunks) {
+        const SaveChunkRecord* after = reloaded.find(before.coord);
+        CHECK(after != nullptr);
+        if (after == nullptr) continue;
+        for (std::size_t i = 0; i < before.blocks.raw().size(); ++i)
+            CHECK(before.blocks.raw()[i] == after->blocks.raw()[i]);
+    }
+
+    ByteBuffer modern = writeSaveContainer(baseContainer());
+    saveWriteU32At(modern.data(), modern.size(), 4, 9u);
+    CHECK_EQ(store.captureMigrated(BackupKind::Full, modern, 10), static_cast<uint32_t>(0));
+    CHECK(store.lastFailure().find("migration") != std::string::npos);
+}
+
+VF_TEST(retentionKeepsTheLatestAndPrunesTheChainsNobodyNeeds) {
+    SaveContainer container = baseContainer();
+    BackupStore store;
+    store.retention.keepLatest = 2;
+    store.retention.dailyBuckets = 1;
+    store.retention.weeklyBuckets = 1;
+
+    std::vector<uint32_t> ids;
+    std::vector<ByteBuffer> saves;
+    const uint64_t ticks[6] = {0, 1000, 24000, 25000, 48000, 49000};
+    const BackupKind kinds[6] = {BackupKind::Full,        BackupKind::Incremental,
+                                 BackupKind::Full,        BackupKind::Incremental,
+                                 BackupKind::Full,        BackupKind::Incremental};
+    for (int step = 0; step < 6; ++step) {
+        replaceChunk(container, {1, 0, 0}, texturedChunk(step));
+        ByteBuffer save = writeSaveContainer(container);
+        uint32_t id = store.capture(kinds[step], save, ticks[step]);
+        CHECK(id != 0u);
+        ids.push_back(id);
+        saves.push_back(save);
+    }
+    CHECK_EQ(store.index().count(), static_cast<std::size_t>(6));
+
+    std::vector<uint32_t> removed = store.prune(49000);
+    CHECK_EQ(removed.size(), static_cast<std::size_t>(4));
+    if (removed.size() == 4) {
+        CHECK_EQ(removed[0], ids[0]);
+        CHECK_EQ(removed[1], ids[1]);
+        CHECK_EQ(removed[2], ids[2]);
+        CHECK_EQ(removed[3], ids[3]);
+    }
+    CHECK_EQ(store.index().count(), static_cast<std::size_t>(2));
+    CHECK(store.index().find(ids[4]) != nullptr);
+    CHECK(store.index().find(ids[5]) != nullptr);
+
+    RestoreResult survivor = store.restore(ids[5]);
+    CHECK(survivor.ok);
+    CHECK(survivor.save == saves[5]);
+    CHECK(!store.restore(ids[1]).ok);
+}
+
+VF_TEST(retentionAlsoKeepsOneBackupPerRecentDay) {
+    ByteBuffer save = writeSaveContainer(baseContainer());
+    BackupStore store;
+    store.retention.keepLatest = 1;
+    store.retention.dailyBuckets = 2;
+    store.retention.weeklyBuckets = 0;
+
+    uint32_t oldest = store.capture(BackupKind::Full, save, 0);
+    uint32_t sameDay = store.capture(BackupKind::Full, save, 100);
+    uint32_t nextDay = store.capture(BackupKind::Full, save, 30000);
+    CHECK(oldest != 0u);
+    CHECK(sameDay != 0u);
+    CHECK(nextDay != 0u);
+
+    std::vector<uint32_t> removed = store.prune(30000);
+    CHECK_EQ(removed.size(), static_cast<std::size_t>(1));
+    if (!removed.empty()) CHECK_EQ(removed[0], oldest);
+    CHECK(store.index().find(sameDay) != nullptr);
+    CHECK(store.index().find(nextDay) != nullptr);
+}
+
+VF_TEST(retentionNeverPrunesAnAncestorAKeptBackupStillNeeds) {
+    SaveContainer container = baseContainer();
+    ByteBuffer save0 = writeSaveContainer(container);
+    replaceChunk(container, {1, 0, 0}, texturedChunk(3));
+    ByteBuffer save1 = writeSaveContainer(container);
+    replaceChunk(container, {2, 0, 0}, texturedChunk(4));
+    ByteBuffer save2 = writeSaveContainer(container);
+
+    BackupStore store;
+    store.retention.keepLatest = 1;
+    store.retention.dailyBuckets = 0;
+    store.retention.weeklyBuckets = 0;
+
+    uint32_t id0 = store.capture(BackupKind::Full, save0, 0);
+    uint32_t id1 = store.capture(BackupKind::Incremental, save1, 1000);
+    uint32_t id2 = store.capture(BackupKind::Incremental, save2, 2000);
+
+    std::vector<uint32_t> removed = store.prune(2000);
+    CHECK(removed.empty());
+    CHECK_EQ(store.index().count(), static_cast<std::size_t>(3));
+    CHECK(store.index().find(id0) != nullptr);
+    CHECK(store.index().find(id1) != nullptr);
+    CHECK(store.restore(id2).save == save2);
+}
+
+VF_TEST(aBrokenChainCannotBeExtendedWithANewIncremental) {
+    SaveContainer container = baseContainer();
+    ByteBuffer save0 = writeSaveContainer(container);
+    replaceChunk(container, {1, 0, 0}, texturedChunk(3));
+    ByteBuffer save1 = writeSaveContainer(container);
+
+    BackupStore store;
+    uint32_t id0 = store.capture(BackupKind::Full, save0, 0);
+    uint32_t id1 = store.capture(BackupKind::Incremental, save1, 1000);
+    CHECK(id1 != 0u);
+    CHECK(store.drop(id0));
+
+    replaceChunk(container, {2, 0, 0}, texturedChunk(5));
+    ByteBuffer save2 = writeSaveContainer(container);
+    CHECK_EQ(store.capture(BackupKind::Incremental, save2, 2000), static_cast<uint32_t>(0));
+    CHECK(store.lastFailure().find("broken chain") != std::string::npos);
+}
+
+VF_TEST(backupKindNamesStayReadable) {
+    CHECK(std::string(backupKindName(BackupKind::Full)) == "full");
+    CHECK(std::string(backupKindName(BackupKind::Incremental)) == "incremental");
+}