diff --git a/tests/git-authenticate.scm b/tests/git-authenticate.scm
index f66ef191b0..6ec55fb2e5 100644
--- a/tests/git-authenticate.scm
+++ b/tests/git-authenticate.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2020, 2022 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,12 +20,17 @@ (define-module (test-git-authenticate)
   #:use-module (git)
   #:use-module (guix git)
   #:use-module (guix git-authenticate)
+  #:use-module ((guix channels) #:select (openpgp-fingerprint))
+  #:use-module ((guix diagnostics)
+                #:select (formatted-message? formatted-message-arguments))
   #:use-module (guix openpgp)
+  #:use-module ((guix tests) #:select (random-text))
   #:use-module (guix tests git)
   #:use-module (guix tests gnupg)
   #:use-module (guix build utils)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-35)
   #:use-module (srfi srfi-64)
   #:use-module (rnrs bytevectors)
   #:use-module (rnrs io ports))
@@ -327,4 +332,103 @@ (define (correct? c commit)
                                        #:keyring-reference "master")
                  'failed)))))))
 
+(unless (gpg+git-available?) (test-skip 1))
+(test-assert "introductory commit, valid signature"
+  (with-fresh-gnupg-setup (list %ed25519-public-key-file
+                                %ed25519-secret-key-file)
+    (let ((fingerprint (key-fingerprint %ed25519-public-key-file)))
+      (with-temporary-git-repository directory
+          `((add "signer.key" ,(call-with-input-file %ed25519-public-key-file
+                                 get-string-all))
+            (add ".guix-authorizations"
+                 ,(object->string
+                   `(authorizations (version 0)
+                                    ((,(key-fingerprint
+                                        %ed25519-public-key-file)
+                                      (name "Charlie"))))))
+            (commit "zeroth commit" (signer ,fingerprint))
+            (add "a.txt" "A")
+            (commit "first commit" (signer ,fingerprint)))
+        (with-repository directory repository
+          (let ((commit0 (find-commit repository "zero"))
+                (commit1 (find-commit repository "first")))
+            ;; COMMIT0 is signed with the right key, and COMMIT1 is fine.
+            (authenticate-repository repository
+                                     (commit-id commit0)
+                                     (openpgp-fingerprint fingerprint)
+                                     #:keyring-reference "master"
+                                     #:cache-key (random-text))))))))
+
+(unless (gpg+git-available?) (test-skip 1))
+(test-equal "introductory commit, missing signature"
+  'intro-lacks-signature
+  (with-fresh-gnupg-setup (list %ed25519-public-key-file
+                                %ed25519-secret-key-file)
+    (let ((fingerprint (key-fingerprint %ed25519-public-key-file)))
+      (with-temporary-git-repository directory
+          `((add "signer.key" ,(call-with-input-file %ed25519-public-key-file
+                                 get-string-all))
+            (add ".guix-authorizations"
+                 ,(object->string
+                   `(authorizations (version 0)
+                                    ((,(key-fingerprint
+                                        %ed25519-public-key-file)
+                                      (name "Charlie"))))))
+            (commit "zeroth commit")              ;unsigned!
+            (add "a.txt" "A")
+            (commit "first commit" (signer ,fingerprint)))
+        (with-repository directory repository
+          (let ((commit0 (find-commit repository "zero")))
+            ;; COMMIT0 is not signed.
+            (guard (c ((formatted-message? c)
+                       ;; Message like "commit ~a lacks a signature".
+                       (and (equal? (formatted-message-arguments c)
+                                    (list (oid->string (commit-id commit0))))
+                            'intro-lacks-signature)))
+              (authenticate-repository repository
+                                       (commit-id commit0)
+                                       (openpgp-fingerprint fingerprint)
+                                       #:keyring-reference "master"
+                                       #:cache-key (random-text)))))))))
+
+(unless (gpg+git-available?) (test-skip 1))
+(test-equal "introductory commit, wrong signature"
+  'wrong-intro-signing-key
+  (with-fresh-gnupg-setup (list %ed25519-public-key-file
+                                %ed25519-secret-key-file
+                                %ed25519-2-public-key-file
+                                %ed25519-2-secret-key-file)
+    (let ((fingerprint (key-fingerprint %ed25519-public-key-file))
+          (wrong-fingerprint (key-fingerprint %ed25519-2-public-key-file)))
+      (with-temporary-git-repository directory
+          `((add "signer1.key" ,(call-with-input-file %ed25519-public-key-file
+                                  get-string-all))
+            (add "signer2.key" ,(call-with-input-file %ed25519-2-public-key-file
+                                  get-string-all))
+            (add ".guix-authorizations"
+                 ,(object->string
+                   `(authorizations (version 0)
+                                    ((,(key-fingerprint
+                                        %ed25519-public-key-file)
+                                      (name "Charlie"))))))
+            (commit "zeroth commit" (signer ,wrong-fingerprint))
+            (add "a.txt" "A")
+            (commit "first commit" (signer ,fingerprint)))
+        (with-repository directory repository
+          (let ((commit0 (find-commit repository "zero"))
+                (commit1 (find-commit repository "first")))
+            ;; COMMIT0 is signed with the wrong key--not the one passed as the
+            ;; SIGNER argument to 'authenticate-repository'.
+            (guard (c ((formatted-message? c)
+                       ;; Message like "commit ~a signed by ~a instead of ~a".
+                       (and (equal? (formatted-message-arguments c)
+                                    (list (oid->string (commit-id commit0))
+                                          wrong-fingerprint fingerprint))
+                            'wrong-intro-signing-key)))
+             (authenticate-repository repository
+                                      (commit-id commit0)
+                                      (openpgp-fingerprint fingerprint)
+                                      #:keyring-reference "master"
+                                      #:cache-key (random-text)))))))))
+
 (test-end "git-authenticate")
