Wrong assertions in block.test

    $bid = db_query("SELECT bid FROM {block_custom} WHERE info = :info", array(':info' => $custom_block['info']))->fetchField();

    // Check to see if the custom block was created by checking that it's in the database.
    $this->assertNotNull($bid, t('Custom block found in database'));

fetchField will return false if there is nothing to fetch or the value of the field if the query gets a result. In both cases assertNotNull is going to be TRUE, so that test is testing nothing at all. The correct assertion would be to assert it is not false, assertTrue.