Whenever you are working on solar cells, you have to realize that they are very fragile. It's possible that they have been compromised during shipping or tabbing or whatever. Because solar cells are strung in series, it is important that they all work at their full potential. Think about what happens when you disconnect a light in old school Christmas lights. The whole string goes out because they are transfered in series. So it's iportant we test them.
In order to test a solar cell for voltage and amperage, you will need a pretty decent multi-meter. If you don't know what that is, you'll see one in a minute. Another thing you will need is something to help you touch both the negative and positive sides of the cell. This can be difficult because they are on opposite sides, and in order to touch them both, the cell would have to be oriented such that it isn't in proper position to collect sunlight. One solution is to use a contraption like the one below.
It's just a clipboard with a strip of flat bus wire taped to it. What that does is make it so that you can place that back side of the solar cell on the bus wire, thus have access to the positive lead.
First, place the cell on the testing tool such that the collector line on the back of the cell is directly on top of the buss wire, as is shown below.