Test chart data

[ADBond]

We don't have many, if any, tests of the actual contents of charts - mostly just that the code runs. It would probably be useful to add some tests to assert that the charts output (at least data-wise) what they should.

For example, before #2309, the completeness chart in Spark scored everything as 100% regardless of column contents, as instead of the actual column name in the SQL, due to a quoting error, it was mistakenly given a string literal (which is always there - it is a literal!).