My file will contain following(log.txt):

start testcase: config loading
......
error XXXX
.....
end testcase: config loading, result failed
start testcase: ping check
.....
error ZZZZZ
.....
error AAAAA
end testcase: Ping check, result failed

I am expecting below output.
=========================================
Testcase: config loading
error XXXX
Testcase: ping check
error ZZZZ
error AAAA
==============================================

There are so many testcases like this in file also the number of error in testcase will vary.

Please give better idea using shell script. Your help will be appreciated.

Thanks