t1400: assert output of update-ref

In t1400-update-ref.sh test 'transaction can create and delete' creates
files "expect" and "actual", but doesn't compare them.  Similarly, test
'transaction cannot restart ongoing transaction' redirects output of
"git update-ref" to file "actual", but doesn't check its contents with
any assertions.

Assert output of "git update-ref" in tests to improve test coverage in
t1400-update-ref.sh.

Signed-off-by: Andrei Rybak <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rybak

t/t1400-update-ref.sh

@@ -1568,6 +1568,7 @@ test_expect_success 'transaction can create and delete' '
 	EOF
 	git update-ref --stdin <stdin >actual &&
 	printf "%s: ok\n" start commit start commit >expect &&
+	test_cmp expect actual &&
 	test_must_fail git show-ref --verify refs/heads/create-and-delete
 '
 
@@ -1595,6 +1596,8 @@ test_expect_success 'transaction cannot restart ongoing transaction' '
 	commit
 	EOF
 	test_must_fail git update-ref --stdin <stdin >actual &&
+	printf "%s: ok\n" start >expect &&
+	test_cmp expect actual &&
 	test_must_fail git show-ref --verify refs/heads/restart
 '