Fix unittests since they were incompatible with the
new testcase and testsuite API.

Bug: v8:6917
Change-Id: I917bf58e21402e0b90bc91c0483ade0e7c90bdd6
Reviewed-on: https://chromium-review.googlesource.com/832392
Commit-Queue: Michał Majewski <majeski@google.com>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50201}