How to click an <option> element with WebDriver?
Besides the correct Qwerky's answer, you can also do simple
driver.findElement(By.xpath("//select/option[@value='1']")).click();
This finds the option
element with value='1'
and clicks it, practically selecting it in the drop-down.
Both mine and Qwerky's solution are described and explained here, in the documentation.
This will select the option with value "1" in the select with id "order_unit_line_rate_806782_is_addenda_enabled".
Select select = (Select)webdriver.findElement(By.id("your id here"));select.selectByValue("1");
You can also select by index or text; see the docs.