Fix = should have been ==. Add some tests for vm type asserts.

test/helper.janet

@@ -21,6 +21,11 @@
      (print e)))
  x)
 
+(defmacro assert-error
+  [msg & forms]
+  (def errsym (keyword (gensym)))
+  ~(assert (= ,errsym (try (do ,;forms) ([_] ,errsym))) ,msg))
+
 (defn start-suite [x]
  (set suite-num x)
  (print "\nRunning test suite " x " tests...\n  "))