I came across this work, "A Review of Digital Literacy Assessment Instruments" (up to 2010). Also this Scholar search (2010-2015) may help find more recent material.
The ImpaCT2 project from Becta had some innovative ways of collecting data on digital literacies, in particular through using concept maps. The Strand 2 report is below:
ImpaCT2: pupils' and teachers' perceptions of ICT in the home, school and community
Somekh, Bridget and Lewin, Cathy and Mavers, Diane and Fisher, Tony and Harrison, Colin and Haw, Kaye and Lunzer, Eric and McFarlane, Angela and Scrimshaw, Peter, British Educational Communications and Technology Agency (BECTA), corp creator. (2002) ImpaCT2: pupils' and teachers' perceptions of ICT in the home, school and community.
With Susan Goldman - I had a grant to look at assessment of digital literacies (which we had to call multiple sources comprehension to get funded ;-)). Here is a write up of the framework - there are others on my profile as well...
I haven't done any work directly in this area; however, I encourage you to visit the research gate page of either Professor Romina Jamieson-Proctor or Professor Glenn Finger who have published work relating to the ICT skills of pre-service and in-service teachers. Regards, Kevin.
I have recently developed a Digital Literacy Scales (DLS). This scale is based on the theoretical framework of 9 C's. The article is yet to be published but we have validated the instrument by using AMOS n it has excellent values.
I think, the dimensions should include knowledge, skills, attitude, and commitment towards electronic tools, systems, devices and resources that generate, store or process data.