diff --git a/test/cache-restore.test.ts b/test/cache-restore.test.ts
index 35c3aa2..a5c2bf8 100644
--- a/test/cache-restore.test.ts
+++ b/test/cache-restore.test.ts
@@ -13,7 +13,7 @@ import {
   MANIFEST_MAIN_FILENAME,
 } from "../src/cache.js";
 import { Manifest, ManifestEntry } from "../src/manifest.js";
-import { ActionPackageNames } from "../src/packages.js";
+import { ActionPackageNames, findInstallScript } from "../src/packages.js";
 
 // Cache resolves its directory from os.homedir(), so point it at a temp dir.
 const { HOME_DIR } = await vi.hoisted(async () => {
@@ -29,6 +29,11 @@ vi.mock("node:os", async (importOriginal) => {
   const actual = await importOriginal<typeof import("node:os")>();
   return { ...actual, homedir: () => HOME_DIR };
 });
+// Restore looks for install scripts under the real "/", so stub the lookup.
+vi.mock("../src/packages.js", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("../src/packages.js")>();
+  return { ...actual, findInstallScript: vi.fn() };
+});
 vi.mock("@actions/cache", () => ({
   restoreCache: vi.fn(),
   saveCache: vi.fn(),
@@ -66,18 +71,20 @@ async function writeCache(archivedPackages = INSTALL_ORDER): Promise<void> {
   archivedPackages.forEach((pkg) => fs.writeFileSync(archivePath(pkg), ""));
 }
 
-/** Archive operations observed through the command runner. */
+/** Archive and install script operations observed through the command runner. */
 interface TarCalls {
   created: [archive: string, files: string[]][];
   extracted: string[];
   /** Number of commands run that extracted archives. */
   extractCommands?: number;
+  /** Extractions and script runs, in the order they ran. */
+  events?: string[];
 }
 
 const argValue = (args: string[], flag: string) =>
   args.find((arg) => arg.startsWith(`${flag}=`))?.slice(flag.length + 1);
 
-/** Records sudo tar calls, including the file list piped to tar create. */
+/** Records sudo tar and script calls, including the file list piped to tar create. */
 function recordTar(calls: TarCalls) {
   return vi.fn(async (_command: string, args: string[] = [], options: CommandOptions = {}) => {
     const archive = argValue(args, "--file") ?? "";
@@ -88,6 +95,11 @@ function recordTar(calls: TarCalls) {
     if (args[0] === "sh" && args[1] === "-c") {
       calls.extracted.push(...args.slice(4));
       calls.extractCommands = (calls.extractCommands ?? 0) + 1;
+      calls.events?.push(...args.slice(4).map((archive) => `extract ${path.basename(archive)}`));
+    }
+    // Install scripts run as `sh -x <script> <action>`.
+    if (args[0] === "sh" && args[1] === "-x") {
+      calls.events?.push(`script ${path.basename(args[2] ?? "")} ${args[3]}`);
     }
     return { cmdLine: "", stdout: "", stderr: "", exitCode: 0 };
   });
@@ -103,6 +115,7 @@ describe("Cache", () => {
     vi.mocked(ghcache.restoreCache).mockResolvedValue(KEY.hash);
     vi.mocked(ghcache.saveCache).mockResolvedValue(CACHE_ID);
     vi.mocked(ghcache.isFeatureAvailable).mockReturnValue(true);
+    vi.mocked(findInstallScript).mockResolvedValue(undefined);
   });
 
   afterEach(() => {
@@ -196,4 +209,103 @@ describe("Cache", () => {
       [REQUESTED_PACKAGE.serialize(), filesOf(REQUESTED_PACKAGE)],
     ]);
   });
+  it("loadAndRestore cache miss returns undefined without extracting", async () => {
+    vi.mocked(ghcache.restoreCache).mockResolvedValue(undefined);
+    const calls: TarCalls = { created: [], extracted: [] };
+
+    const manifest = await createCache(calls).loadAndRestore(KEY, false);
+
+    expect(manifest).toBeUndefined();
+    expect(calls.extracted).toEqual([]);
+  });
+
+  it.each([
+    ["main manifest missing", MANIFEST_MAIN_FILENAME, undefined],
+    ["all manifest missing", MANIFEST_ALL_FILENAME, undefined],
+    ["all manifest empty", MANIFEST_ALL_FILENAME, new Manifest(MANIFEST.created, [], KEY)],
+  ])("loadAndRestore %s returns undefined without extracting", async (_case, filename, replacement) => {
+    await writeCache();
+    const filePath = path.join(CACHE_DIR, filename);
+    fs.rmSync(filePath);
+    await replacement?.writeToFile(filePath);
+    const calls: TarCalls = { created: [], extracted: [] };
+
+    const manifest = await createCache(calls).loadAndRestore(KEY, false);
+
+    expect(manifest).toBeUndefined();
+    expect(calls.extracted).toEqual([]);
+  });
+
+  it("loadAndRestore cache hit without cache directory logs it as unreadable and returns undefined", async () => {
+    const logger = winston.createLogger({ silent: true });
+    const errorSpy = vi.spyOn(logger, "error");
+    const cache = new Cache({ run: vi.fn() } as never, logger);
+
+    const manifest = await cache.loadAndRestore(KEY, false);
+
+    expect(manifest).toBeUndefined();
+    expect(errorSpy).toHaveBeenCalledWith(expect.stringContaining("Unable to read cache directory contents"));
+  });
+
+  it("loadAndRestore only packages without files runs no extract command", async () => {
+    fs.mkdirSync(CACHE_DIR, { recursive: true });
+    const metaOnly = new Manifest(MANIFEST.created, [new ManifestEntry(METAPACKAGE)], KEY);
+    await metaOnly.writeToFile(path.join(CACHE_DIR, MANIFEST_MAIN_FILENAME));
+    await metaOnly.writeToFile(path.join(CACHE_DIR, MANIFEST_ALL_FILENAME));
+    const calls: TarCalls = { created: [], extracted: [] };
+
+    const manifest = await createCache(calls).loadAndRestore(KEY, false);
+
+    expect(manifest?.entries).toHaveLength(1);
+    expect(calls.extractCommands).toBeUndefined();
+  });
+
+  it("loadAndRestore with install scripts runs each found script after its archive with the dpkg action", async () => {
+    await writeCache();
+    const [first, second] = INSTALL_ORDER;
+    vi.mocked(findInstallScript).mockImplementation(async (packageName, scriptType) =>
+      packageName.name === first!.name ? `/var/lib/dpkg/info/${packageName.name}.${scriptType}` : undefined,
+    );
+    const calls: TarCalls = { created: [], extracted: [], events: [] };
+
+    await createCache(calls).loadAndRestore(KEY, true);
+
+    expect(calls.events?.slice(0, 4)).toEqual([
+      `extract ${path.basename(archivePath(first!))}`,
+      `script ${first!.name}.preinst install`,
+      `script ${first!.name}.postinst configure`,
+      `extract ${path.basename(archivePath(second!))}`,
+    ]);
+  });
+
+  it("archiveAndSave cache service unavailable throws without archiving", async () => {
+    vi.mocked(ghcache.isFeatureAvailable).mockReturnValue(false);
+    const calls: TarCalls = { created: [], extracted: [] };
+
+    await expect(createCache(calls).archiveAndSave(MANIFEST)).rejects.toThrow("not available");
+    expect(calls.created).toEqual([]);
+  });
+
+  it("archiveAndSave archive already exists skips recreating it", async () => {
+    const [existing, ...rest] = INSTALL_ORDER;
+    fs.mkdirSync(CACHE_DIR, { recursive: true });
+    fs.writeFileSync(archivePath(existing!), "");
+    const calls: TarCalls = { created: [], extracted: [] };
+
+    await createCache(calls).archiveAndSave(MANIFEST);
+
+    expect(calls.created.map(([archive]) => archive)).toEqual(rest.map(archivePath));
+  });
+
+  it.each([
+    ["no cache ID", () => Promise.resolve(undefined), "no cache action ID returned"],
+    ["an Error", () => Promise.reject(new Error("upload failed")), "upload failed"],
+    ["a non-Error", () => Promise.reject("upload failed"), "upload failed"],
+  ])("archiveAndSave save returns %s throws a save error", async (_case, saveResult, message) => {
+    vi.mocked(ghcache.saveCache).mockImplementation(saveResult as never);
+
+    await expect(createCache().archiveAndSave(MANIFEST)).rejects.toThrow(
+      new RegExp(`^Failed to save cache: .*${message}`),
+    );
+  });
 });
diff --git a/test/manifest.test.ts b/test/manifest.test.ts
index 49496b2..43fd193 100644
--- a/test/manifest.test.ts
+++ b/test/manifest.test.ts
@@ -37,4 +37,15 @@ describe("manifest", () => {
     expect(parsed.entries).toHaveLength(1);
     expect(parsed.entries[0]?.packageName.serialize()).toBe("curl:amd64=8.1.0");
   });
+
+  it("ManifestEntry fromJSON parsed entry returns package and sorted files", () => {
+    const entry = new ManifestEntry(createPackageName("curl", "8.1.0", "amd64"), [
+      "usr/bin/curl",
+      "etc/curlrc",
+    ]);
+
+    const parsed = ManifestEntry.fromJSON(JSON.parse(JSON.stringify(entry)));
+
+    expect(parsed).toEqual(entry);
+  });
 });
diff --git a/test/packages.test.ts b/test/packages.test.ts
index 0483c76..ca46072 100644
--- a/test/packages.test.ts
+++ b/test/packages.test.ts
@@ -101,6 +101,42 @@ describe("packages", () => {
     expect(result).toBeUndefined();
   });
 
+  it("buildFileList installed paths missing on disk excludes them", async () => {
+    const root = makeTempRoot("pkg-missing-file-");
+    const presentFile = path.join(root, "present");
+    fs.writeFileSync(presentFile, "", "utf8");
+    const manager = {
+      listInstalledFiles: vi.fn().mockResolvedValue([presentFile, path.join(root, "absent")]),
+    };
+
+    const result = await buildFileList(PACKAGE_NAME, manager as any, root);
+
+    expect(result).toEqual([presentFile.slice(1)]);
+  });
+
+  it("updateAptLists lists directory with files skips update", async () => {
+    const aptListsPath = makeTempRoot("apt-lists-populated-");
+    fs.mkdirSync(path.join(aptListsPath, "partial"));
+    fs.writeFileSync(path.join(aptListsPath, "partial", "archive_Packages"), "", "utf8");
+    const packageManager = { update: vi.fn() };
+
+    await updateAptLists(packageManager as any, { info: vi.fn() } as any, aptListsPath);
+
+    expect(packageManager.update).not.toHaveBeenCalled();
+  });
+
+  it("updateAptLists files only below max search depth runs update", async () => {
+    const aptListsPath = makeTempRoot("apt-lists-deep-");
+    const deepDir = path.join(aptListsPath, "a", "b", "c", "d", "e");
+    fs.mkdirSync(deepDir, { recursive: true });
+    fs.writeFileSync(path.join(deepDir, "archive_Packages"), "", "utf8");
+    const packageManager = { update: vi.fn().mockResolvedValue(undefined) };
+
+    await updateAptLists(packageManager as any, { info: vi.fn() } as any, aptListsPath);
+
+    expect(packageManager.update).toHaveBeenCalledTimes(1);
+  });
+
   it("updateAptLists calls the package manager's update method", async () => {
     const aptListsPath = makeTempRoot("apt-lists-");
 
@@ -128,6 +164,12 @@ describe("packages", () => {
       ]);
     });
 
+    it("fromInput version without package name ignores the token", () => {
+      const result = ActionPackageNames.fromInput("=1.0.0 curl");
+
+      expect(result.toArray()).toEqual([createPackageName("curl")]);
+    });
+
     it("fromInput returns an empty list when input is empty", () => {
       const result = ActionPackageNames.fromInput("");
       expect(result.toArray()).toEqual([]);