It was possible to write tests but pass by reference is a "feature" of Fortran IV.

   A subroutine receives values from the caller through 
   the parameter list; likewise, the subroutine returns
   values by modifying the variables in the parameter
   list.  Subroutines are invoked in a FORTRAN program
   as a statement, not an expression.  The syntax used 
   is, 
        CALL name(actualParamList)

See you modify the parameter to send a return value. Really ancient stuff. And if you're working on hardware that is challenged in not having a "load immediate" instruction for floating point, well you get "optimizations" where the compiler creates what is essentially a pre-initialized variable and uses the address of that when a constant is used.