to start testnet of bitcoin,you must use   Original Bitcoin Client .

step1:right click the bitcion-qt.exe and create a shortcut

https://vcex.co/data/attachment/portal/201308/07/014642p85r8z5svp4rz5w6.png


step2:right click the   shortcut and edit properties
https://vcex.co/data/attachment/portal/201308/07/014838teffmhx2eox0ucot.png


step3:add -testnet  to the target and change icon


https://vcex.co/data/attachment/portal/201308/07/015121udjstrdbrl6t61vb.png
select the icon you like

https://vcex.co/data/attachment/portal/201308/07/015145al08e6zyo9eniavi.png

step4:save the shortcut and run it
https://vcex.co/data/attachment/portal/201308/07/015346ahhdw5w9w3v3wh4r.png

if you want to mine ,just add -gen at step3 ,then enjoy it !
https://vcex.co/data/attachment/portal/201308/07/015552nxdflsfszlfxfdxr.png


https://vcex.co/data/attachment/portal/201308/07/015913hsn5q406hpcn5kyh.png