Unit test with Table-driven style

## Feature Request

In current unit test coverage situation, I found that, in most cases, the error handling hasn't been covered due to we only prepared the success cases in current unit test.

Here is one example:


To cover the error handling in the function, I'd like to introduce the [`Table-driven`](https://github.com/golang/go/wiki/TableDrivenTests#parallel-testing) ut style.

Here is one example to show how we use table-driver style to cover the error handling cases.

https://github.com/pingcap/pd/pull/2589