Allow for overriding current time via special variables

clock.lisp

@@ -2,5 +2,11 @@
 
 (in-package #:ginkgo-time)
 
+(defparameter *clock-now* nil)
+(defparameter *clock-now-function* nil)
+
 (defun clock-now ()
-  (trivial-clock:now))
+  (cond
+   (*clock-now* (values-list *clock-now*))
+   (*clock-now-function* (funcall *clock-now-function*))
+   (t (trivial-clock:now))))

package.lisp

@@ -25,6 +25,8 @@
    #:chrono-unit-duration
 
    ;; clock.lisp
+   #:*clock-now*
+   #:*clock-now-function*
    #:clock-now
 
    ;; instant.lisp