tests: Move some of the narinfo test tools to (guix tests).

* guix/tests.scm (derivation-narinfo, call-with-derivation-narinfo): New
  procedures.
  (with-derivation-narinfo): New macro.
* tests/derivations.scm ("derivation-prerequisites-to-build and
  substitutes"): Use them.

guix/tests.scm

@@ -23,9 +23,11 @@ (define-module (guix tests)
   #:use-module (gnu packages bootstrap)
   #:use-module (srfi srfi-34)
   #:use-module (rnrs bytevectors)
+  #:use-module (web uri)
   #:export (open-connection-for-tests
             random-text
-            random-bytevector))
+            random-bytevector
+            with-derivation-narinfo))
 
 ;;; Commentary:
 ;;;
@@ -67,4 +69,59 @@ (define (random-bytevector n)
             (loop (1+ i)))
           bv))))
 
+
+;;;
+;;; Narinfo files, as used by the substituter.
+;;;
+
+(define* (derivation-narinfo drv #:optional (nar "example.nar"))
+  "Return the contents of the narinfo corresponding to DRV; NAR should be the
+file name of the archive containing the substitute for DRV."
+  (format #f "StorePath: ~a
+URL: ~a
+Compression: none
+NarSize: 1234
+References: 
+System: ~a
+Deriver: ~a~%"
+          (derivation->output-path drv)       ; StorePath
+          nar                                 ; URL
+          (derivation-system drv)             ; System
+          (basename
+           (derivation-file-name drv))))      ; Deriver
+
+(define (call-with-derivation-narinfo drv thunk)
+  "Call THUNK in a context where fake substituter data, as read by 'guix
+substitute-binary', has been installed for DRV."
+  (let* ((output  (derivation->output-path drv))
+         (dir     (uri-path
+                   (string->uri (getenv "GUIX_BINARY_SUBSTITUTE_URL"))))
+         (info    (string-append dir "/nix-cache-info"))
+         (narinfo (string-append dir "/" (store-path-hash-part output)
+                                 ".narinfo")))
+    (dynamic-wind
+      (lambda ()
+        (call-with-output-file info
+          (lambda (p)
+            (format p "StoreDir: ~a\nWantMassQuery: 0\n"
+                    (%store-prefix))))
+        (call-with-output-file narinfo
+          (lambda (p)
+            (display (derivation-narinfo drv) p))))
+      thunk
+      (lambda ()
+        (delete-file narinfo)
+        (delete-file info)))))
+
+(define-syntax-rule (with-derivation-narinfo drv body ...)
+  "Evaluate BODY in a context where DRV looks substitutable from the
+substituter's viewpoint."
+  (call-with-derivation-narinfo drv
+    (lambda ()
+      body ...)))
+
+;; Local Variables:
+;; eval: (put 'call-with-derivation-narinfo 'scheme-indent-function 1)
+;; End:
+
 ;;; tests.scm ends here

tests/derivations.scm

@@ -567,43 +567,21 @@ (define %coreutils
   (let* ((store  (open-connection))
          (drv    (build-expression->derivation store "prereq-subst"
                                                (random 1000)))
-         (output (derivation->output-path drv))
-         (dir    (and=> (getenv "GUIX_BINARY_SUBSTITUTE_URL")
-                        (compose uri-path string->uri))))
-    ;; Create fake substituter data, to be read by `substitute-binary'.
-    (call-with-output-file (string-append dir "/nix-cache-info")
-      (lambda (p)
-        (format p "StoreDir: ~a\nWantMassQuery: 0\n"
-                (%store-prefix))))
-    (call-with-output-file (string-append dir "/" (store-path-hash-part output)
-                                          ".narinfo")
-      (lambda (p)
-        (format p "StorePath: ~a
-URL: ~a
-Compression: none
-NarSize: 1234
-References: 
-System: ~a
-Deriver: ~a~%"
-                output                              ; StorePath
-                (string-append dir "/example.nar")  ; URL
-                (%current-system)                   ; System
-                (basename
-                 (derivation-file-name drv)))))     ; Deriver
+         (output (derivation->output-path drv)))
 
     ;; Make sure substitutes are usable.
     (set-build-options store #:use-substitutes? #t)
 
-    (let-values (((build download)
-                  (derivation-prerequisites-to-build store drv))
-                 ((build* download*)
-                  (derivation-prerequisites-to-build store drv
-                                                     #:use-substitutes? #f)))
-      (pk build download build* download*)
-      (and (null? build)
-           (equal? download (list output))
-           (null? download*)
-           (null? build*)))))
+    (with-derivation-narinfo drv
+      (let-values (((build download)
+                    (derivation-prerequisites-to-build store drv))
+                   ((build* download*)
+                    (derivation-prerequisites-to-build store drv
+                                                       #:use-substitutes? #f)))
+        (and (null? build)
+             (equal? download (list output))
+             (null? download*)
+             (null? build*))))))
 
 (test-assert "build-expression->derivation with expression returning #f"
   (let* ((builder  '(begin
@@ -901,3 +879,7 @@ (define (deps path . deps)
 
 
 (exit (= (test-runner-fail-count (test-runner-current)) 0))
+
+;; Local Variables:
+;; eval: (put 'with-derivation-narinfo 'scheme-indent-function 1)
+;; End: