Hey Tommy,
if the `Button` has graphics instead of (unique) text you need another way to query it.
The easiest way is to set the `Button`'s id and use `clickOn("#id")`, where "id" is the id you use.
Another way is to query the table cell (in which the button is) first and then to query `.button`, iff the table cell contains only a single button.
Here is a code example (for TestFX 4.0.3-alpha). "#myTableView" is the id of your `TableView`, rowIndex the table row index and columnIndex the table column index.
~~~java
clickOn(lookup("#myTableView")
.lookup(".table-row-cell").nth(rowIndex)
.lookup(".table-cell").nth(columnIndex)
.lookup(".button").query())
~~~
--Benjamin