export API to set RefTime of Updater (#641)

* export API to set RefTime of Updater

Signed-off-by: Adam Korczynski <adam@adalogics.com>

* Update metadata/updater/updater.go

Co-authored-by: Fredrik Skogman <kommendorkapten@github.com>
Signed-off-by: AdamKorcz <44787359+AdamKorcz@users.noreply.github.com>

* update name in test

Signed-off-by: Adam Korczynski <adam@adalogics.com>

* add comment to UnsafeSetRefTime

Signed-off-by: Adam Korczynski <adam@adalogics.com>

* Update metadata/updater/updater.go

Co-authored-by: Fredrik Skogman <kommendorkapten@github.com>
Signed-off-by: AdamKorcz <44787359+AdamKorcz@users.noreply.github.com>

---------

Signed-off-by: Adam Korczynski <adam@adalogics.com>
Signed-off-by: AdamKorcz <44787359+AdamKorcz@users.noreply.github.com>
Co-authored-by: Fredrik Skogman <kommendorkapten@github.com>

Author: AdamKorcz

metadata/updater/updater.go

@@ -662,6 +662,13 @@ func (update *Updater) GetTrustedMetadataSet() trustedmetadata.TrustedMetadata {
 	return *update.trusted
 }
 
+// UnsafeSetRefTime sets the reference time that the updater uses.
+// This should only be done in tests.
+// Using this function is useful when testing time-related behavior in go-tuf.
+func (update *Updater) UnsafeSetRefTime(t time.Time) {
+	update.trusted.RefTime = t
+}
+
 func IsWindowsPath(path string) bool {
 	match, _ := regexp.MatchString(`^[a-zA-Z]:\\`, path)
 	return match

metadata/updater/updater_top_level_update_test.go

@@ -98,7 +98,7 @@ func runRefresh(updaterConfig *config.UpdaterConfig, moveInTime time.Time) (Upda
 	}
 
 	if moveInTime != time.Now() {
-		updater.trusted.RefTime = moveInTime
+		updater.UnsafeSetRefTime(moveInTime)
 	}
 
 	return *updater, updater.Refresh()