io: assert errors before asserting content in I/O test

When checking the results of an I/O operation test, assert that
the error objects are NULL before asserting on the content. This
is found to give more useful indication of the problem when
diagnosing test failures.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

tests/io-channel-helpers.c

@@ -233,11 +233,11 @@ void qio_channel_test_run_reader(QIOChannelTest *test,
 
 void qio_channel_test_validate(QIOChannelTest *test)
 {
+    g_assert(test->readerr == NULL);
+    g_assert(test->writeerr == NULL);
     g_assert_cmpint(memcmp(test->input,
                            test->output,
                            test->len), ==, 0);
-    g_assert(test->readerr == NULL);
-    g_assert(test->writeerr == NULL);
 
     g_free(test->inputv);
     g_free(test->outputv);