When I was playing this game (very very long time ago) I had the same problem, in ODI's I'd get all kinds of wickets, edge chances, edges through gaps etc and in tests literally nothing would just be bowling for hours and became really boring. At least getting chances would be nice.
What has the game became btw with all recent patches etc? Is it better or is it patches that make game worse?
I put a rough highlights video in the game play thread that shows me bowling at the AI. Had them all done in 70 overs, with England scoring 3 an over. Was really satisfying.
I was bowling exclusively in career mode and rarely if ever taking wickets. This was like night and day by comparison.
In that game, I had some success bowling a good length, but after lunch Cummins and Hazelwood bowled fuller and the wickets really started to fall. Was noticeable that a full ball was bringing me much more success.