diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index 68b920a4dd41..ac9a23e0408e 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -574,6 +574,7 @@ in
     _module.args.firefoxPackage = pkgs.firefox-esr-140;
   };
   firefox-syncserver = runTest ./firefox-syncserver.nix;
+  firefox_decrypt = runTest ./firefox_decrypt.nix;
   firefoxpwa = runTest ./firefoxpwa.nix;
   firejail = runTest ./firejail.nix;
   firewall = runTest {
diff --git a/nixos/tests/firefox_decrypt.nix b/nixos/tests/firefox_decrypt.nix
new file mode 100644
index 000000000000..4612f122214e
--- /dev/null
+++ b/nixos/tests/firefox_decrypt.nix
@@ -0,0 +1,73 @@
+{ lib, ... }:
+{
+  name = "firefox_decrypt";
+
+  meta = {
+    maintainers = with lib.maintainers; [ schnusch ];
+  };
+
+  nodes.machine =
+    { pkgs, ... }:
+    {
+      imports = [ ./common/x11.nix ];
+      programs.firefox.enable = true;
+      environment.systemPackages = [ pkgs.firefox_decrypt ];
+    };
+
+  enableOCR = true;
+
+  testScript = ''
+    import csv
+    import io
+    import random
+    import string
+
+    machine.wait_for_x()
+
+    expected: dict[str, str] = {
+        "url": "http://localhost",
+        "user": "user",
+        "password": "".join(random.choices(string.ascii_letters + string.digits, k=32)),
+    }
+
+    machine.execute("firefox about:logins >&2 &")
+
+    # press "Add password" button
+    # "Search Passwords" is not found by OCR, probably due to too low contrast.
+    machine.wait_for_text("No passwords saved")
+    for c in ("tab", "\n"):
+        machine.send_key(c)
+
+    # add a new password entry
+    machine.wait_for_text("Add password")
+    for text, control in [
+        (expected["url"], "tab"),
+        (expected["user"], "tab"),
+        (expected["password"], "\n"),
+    ]:
+        with machine.nested(f"typing {repr(text)}"):
+            for c in text:
+                machine.send_key(c, log=False)
+        machine.send_key(control)
+
+    # "Remove" button for our new entry appeared
+    machine.wait_for_text("Remove")
+
+    # close Firefox
+    machine.send_key("ctrl-q")
+    machine.wait_for_text(r"Quit Firefox or close current tab\?")
+    machine.send_key("\n")
+
+    # extract Firefox logins
+    credentials = list(
+        csv.DictReader(
+            io.StringIO(
+                machine.succeed("firefox_decrypt -f csv ~/.config/mozilla/firefox"),
+                newline="",
+            ),
+            delimiter=";",
+        )
+    )
+    assert expected in credentials, f"expected {expected!r} in {credentials!r}"
+  '';
+}
diff --git a/pkgs/by-name/fi/firefox_decrypt/package.nix b/pkgs/by-name/fi/firefox_decrypt/package.nix
index 0dba1e092146..7b1412d14352 100644
--- a/pkgs/by-name/fi/firefox_decrypt/package.nix
+++ b/pkgs/by-name/fi/firefox_decrypt/package.nix
@@ -2,6 +2,7 @@
   lib,
   fetchFromGitHub,
   nss,
+  nixosTests,
   nix-update-script,
   stdenv,
   python3Packages,
@@ -32,7 +33,12 @@ python3Packages.buildPythonApplication (finalAttrs: {
     (lib.makeLibraryPath [ nss ])
   ];
 
-  passthru.updateScript = nix-update-script { };
+  passthru = {
+    tests = {
+      inherit (nixosTests) firefox_decrypt;
+    };
+    updateScript = nix-update-script { };
+  };
 
   meta = {
     homepage = "https://github.com/unode/firefox_decrypt";