Hydroforming has been selected as a technique for the seamless fabrication of multicell superconducting radiofrequency (SRF) cavities. For the successful application of this technique to cavity fabrication, it is essential to understand deformation behavior of tubes under hydroforming conditions. Input to the finite-element modeling (FEM) which generally precedes the actual hydroforming process requires the constitutive properties of the tube material. This information may be obtained from the results of hydraulic bulge testing. The present paper provides an example of this activity. In order to verify the steps to be taken in analyzing future bulge-test data a circular argument recovers the original constitutive properties from the results of an FEM-based "virtual bulge test".