Resolution of cross references doesn't work in special row combination

[sparsick]

Given following expected table with cross references throws NumberFormatException :

x (String)	y (int)	z (int)
x	${test}	3
x	5	6

The computed table looks

x (String)	y (int)	z (int)
x	2	3
x	5	6

The reason for the exception is that the original RowFixture tries to use ${test} as key and parsing to int fails.

[jochenwierum]

Fixed by #25