Simplify and extend using the knots exception with stack

tests/thread-pool.scm

@@ -2,6 +2,7 @@
              (srfi srfi-71)
              (fibers)
              (unit-test)
+             (knots)
              (knots thread-pool))
 
 (let ((thread-pool
@@ -41,4 +42,21 @@
 
   (process-job 3))
 
+(let ((thread-pool
+       (make-thread-pool 2)))
+
+  (run-fibers-for-tests
+   (lambda ()
+     (assert-equal
+      #t
+      (with-exception-handler
+          (lambda (exn)
+            (knots-exception? exn))
+        (lambda ()
+          (call-with-thread
+           thread-pool
+           (lambda ()
+             (+ 1 'a))))
+        #:unwind? #t)))))
+
 (display "thread-pool test finished successfully\n")