services: openntpd: Add test for issue #3731.

See http://debbugs.gnu.org/cgi/bugreport.cgi?bug=37318.

* gnu/services/networking.scm (openntpd-configuration->string): New procedure,
extracted from top of the `openntpd-shepherd-service' to make it testable.
(openntpd-shepherd-service): Adapt following the move of the code to the above
procedure.
* tests/networking.scm: Add a test for the `openntpd-configuration->string'
procedure.

gnu/services/networking.scm

@@ -504,12 +504,10 @@ make an initial adjustment of more than 1,000 seconds."
   (allow-large-adjustment? openntpd-allow-large-adjustment?
                            (default #f))) ; upstream default
 
-(define (openntpd-shepherd-service config)
+(define (openntpd-configuration->string config)
   (match-record config <openntpd-configuration>
-    (openntpd listen-on query-from sensor server servers constraint-from
+    (listen-on query-from sensor server servers constraint-from
-              constraints-from allow-large-adjustment?)
+               constraints-from)
-
-    (define config
     (string-join
      (filter-map
       (lambda (field value)
@@ -522,10 +520,14 @@ make an initial adjustment of more than 1,000 seconds."
      ;; The 'constraints from' field needs to be enclosed in double quotes.
      (string-join
       (map (cut string-append "constraints from \"" <> "\"\n")
-             constraints-from))))
+           constraints-from)))))
+
+(define (openntpd-shepherd-service config)
+  (let ((openntpd (openntpd-configuration-openntpd config))
+        (allow-large-adjustment? (openntpd-allow-large-adjustment? config)))
 
     (define ntpd.conf
-      (plain-file "ntpd.conf" config))
+      (plain-file "ntpd.conf" (openntpd-configuration->string config)))
 
     (list (shepherd-service
            (provision '(ntpd))

tests/networking.scm

@@ -17,11 +17,19 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (tests networking)
+  #:use-module (ice-9 regex)
   #:use-module (gnu services networking)
   #:use-module (srfi srfi-64))
 
 ;;; Tests for the (gnu services networking) module.
 
+(test-begin "networking")
+
+
+;;;
+;;; NTP.
+;;;
+
 (define ntp-server->string (@@ (gnu services networking) ntp-server->string))
 
 (define %ntp-server-sample
@@ -30,8 +38,6 @@
    (address "some.ntp.server.org")
    (options `(iburst (version 3) (maxpoll 16) prefer))))
 
-(test-begin "networking")
-
 (test-equal "ntp-server->string"
   (ntp-server->string %ntp-server-sample)
   "server some.ntp.server.org iburst version 3 maxpoll 16 prefer")
@@ -47,4 +53,61 @@
    (ntp-configuration
     (servers (list "example.pool.ntp.org")))))
 
+
+;;;
+;;; OpenNTPD
+;;;
+
+(define openntpd-configuration->string (@@ (gnu services networking)
+                                           openntpd-configuration->string))
+
+(define %openntpd-conf-sample
+  (openntpd-configuration
+   (server '("0.guix.pool.ntp.org" "1.guix.pool.ntp.org"))
+   (listen-on '("127.0.0.1" "::1"))
+   (sensor '("udcf0 correction 70000"))
+   (constraint-from '("www.gnu.org"))
+   (constraints-from '("https://www.google.com/"))
+   (allow-large-adjustment? #t)))
+
+(test-assert "openntpd configuration generation sanity check"
+
+  (begin
+    (define (string-match/newline pattern text)
+      (regexp-exec (make-regexp pattern regexp/newline) text))
+
+    (define (match-count pattern text)
+      (fold-matches (make-regexp pattern regexp/newline) text 0
+                    (lambda (match count)
+                      (1+ count))))
+
+    (let ((config (openntpd-configuration->string %openntpd-conf-sample)))
+      (if (not
+           (and (string-match/newline "^listen on 127.0.0.1$" config)
+                (string-match/newline "^listen on ::1$" config)
+                (string-match/newline "^sensor udcf0 correction 70000$" config)
+                (string-match/newline "^constraint from www.gnu.org$" config)
+                (string-match/newline "^server 0.guix.pool.ntp.org$" config)
+                (string-match/newline
+                 "^constraints from \"https://www.google.com/\"$"
+                 config)
+
+                ;; Check for issue #3731 (see:
+                ;; http://debbugs.gnu.org/cgi/bugreport.cgi?bug=37318).
+                (= (match-count "^listen on " config) 2)
+                (= (match-count "^sensor " config) 1)
+                (= (match-count "^constraint from " config) 1)
+                (= (match-count "^server " config) 2)
+                (= (match-count "^constraints from " config) 1)))
+          (begin
+            (format #t "The configuration below failed \
+the sanity check:\n~a~%" config)
+            #f)
+          #t))))
+
+(test-equal "openntpd generated config string ends with a newline"
+  (let ((config (openntpd-configuration->string %openntpd-conf-sample)))
+    (string-take-right config 1))
+  "\n")
+
 (test-end "networking")