Tests: Add ts-fill

This may fail on Emacs 28.0.50.  See
<#18>.

test/test.el

@@ -429,6 +429,24 @@
  (should (= (- (ts-year now) (ts-year then))
  expected-difference))))
 
+(ert-deftest ts-fill ()
+ (let ((ts (ts-fill (make-ts :unix 1625426636.7569551))))
+ (should (equal (ts-year ts) 2021))
+ (should (equal (ts-month-num ts) 7))
+ (should (equal (ts-day-of-month-num ts) 4))
+ (should (equal (ts-day-of-week-num ts) 0))
+ (should (equal (ts-hour ts) 14))
+ (should (equal (ts-minute ts) 23))
+ (should (equal (ts-second ts) 56))
+ (should (equal (ts-month-name ts) "July"))
+ (should (equal (ts-month-abbr ts) "Jul"))
+ (should (equal (ts-day-abbr ts) "Sun"))
+ (should (equal (ts-day-name ts) "Sunday"))
+ (should (equal (ts-day-of-year ts) 185))
+ (should (equal (ts-week-of-year ts) 26))
+ (should (equal (ts-tz-abbr ts) "CDT"))
+ (should (equal (ts-tz-offset ts) "-0500"))))
+
 (ert-deftest ts-now ()
  "Ensure `ts-now' returns what appears to be the current time."
  (should (equal (floor (ts-unix (ts-now)))