What does "tester" mean?

Additional senses

1. 2.A canopy over a bed, supported by the bedposts. No testers to the bed, and the saddles and portmanteaus heaped on me to keep off the cold. Walpole.
2. 3.An old French silver coin, originally of the value of about eighteen pence, subsequently reduced to ninepence, and later to sixpence, sterling. Hence, in modern English slang, a sixpence; -- often contracted to tizzy. Called also teston. Shak.