Ensures that content is rebuilt in calls to custom_block_build_content().
public function testCustomBlockRebuildContent() {
$block = $this
->createCustomBlock();
// Set a property in the content array so we can test for its existence later on.
$block->content['test_content_property'] = array(
'#value' => $this
->randomString(),
);
$content = entity_view_multiple(array(
$block,
), 'full');
// If the property doesn't exist it means the block->content was rebuilt.
$this
->assertFalse(isset($content['test_content_property']), 'Custom block content was emptied prior to being built.');
}