Add a mock-inferior module

This to help test code which uses the (guix inferior) module.

tests/mock-inferior.scm

@@ -0,0 +1,45 @@
+(define-module (tests mock-inferior)
+  #:use-module (guix records)
+  #:use-module (guix tests)
+  #:export (<mock-inferior-package>
+            mock-inferior-package
+            mock-inferior-package?
+            mock-inferior-package-name
+            mock-inferior-package-version
+            mock-inferior-package-synopsis
+            mock-inferior-package-description
+            mock-inferior-package-home-page
+
+            with-mock-inferior-packages))
+
+(define-record-type* <mock-inferior-package>
+  mock-inferior-package make-mock-inferior-pacakge
+  mock-inferior-package?
+  (name        mock-inferior-package-name)
+  (version     mock-inferior-package-version)
+  (synopsis    mock-inferior-package-synopsis)
+  (description mock-inferior-package-description)
+  (home-page   mock-inferior-package-home-page))
+
+(define (with-mock-inferior-packages f)
+  (mock
+   ((guix inferior)
+    inferior-package-name
+    mock-inferior-package-name)
+   (mock
+    ((guix inferior)
+     inferior-package-version
+     mock-inferior-package-version)
+    (mock
+     ((guix inferior)
+      inferior-package-synopsis
+      mock-inferior-package-synopsis)
+     (mock
+      ((guix inferior)
+       inferior-package-description
+       mock-inferior-package-description)
+      (mock
+       ((guix inferior)
+        inferior-package-home-page
+        mock-inferior-package-home-page)
+       (f)))))))