The main thing you need to consider is that a week now of rest won't affect your fitness level as much as about a month or two off running if your calf doesnt get better or gets worse. I used to go through a few months of amazing training then get attacked by the dreaded shin splints, and i'd run through them instead of taking a few days off then they would get worse and i would be off for a few months. this went on for about 2 years for me and the worst they got was for me hgaving to take 6 months off running. that hurts. Now I listen to my body a lot better and stretch well- taking a few extra rest days if Im not recovering very well. If you think your ready for running try a small run and test it out. Your main concern right now should be getting back into the running groove, not your 5km test run. It sounds as if you have increased your running mileage- wich could be the cause of the discomfort, but there could be other reasons that your calf cramped up ie. dehydration or lack of potassium.

Anyways- good luck!

Hey. How is your calf doing? I saw your post and I wanted to check in. I had a similar thing happen to me in a game in high school and I kept playing and tore part of my calf. Ouch! So when I saw your post I was very interested. Anyway, I wanted to see how things were going with you. Hopefully it was just due to dehydration and you are back out there training for your 5k. Hope all is well!

Also, I found this thread after I just posted. It talks about calf pain and different ways of running to help.

http://community.active.com/message/465399#465399