There is no Coupled Differential System for now @asmeurer 
That is we need to work out for a method such that we can solve 
```
  Matrix( dy1,     +   Matrix( b1, ab2    Matrix(y1,    =      Matrix(c1,
               dy2 )                      b2 , b1)                y2)        c2)
```
< i hope the above conveys the feel>
for the test added, we would have a call for CDS function with 
b1 = 0
b2 = 1
c1 = 2/x
c2 = 0
which has no solution for the above equation and hence returns " NO solutiom"
but for the test in the XFAIL we would require cds to return a valid solution for the above equation and hence as we have no support for cds