amp-pixel: Minor test improvements (#26918)
amp-pixel: Minor test improvements (#26918)

* amp-pixel: Minor test improvements

Expect console errors.

* amp-pixel: Revisions from review

Create reusable regex for tests.

yandex-pcode/amphtml,voyagegroup/amphtml,mhc-gh/amphtml,prateekbh/amphtml,honeybadgerdontcare/amphtml,alanorozco/amphtml,voyagegroup/amphtml,mhc-gh/amphtml,media-net/amphtml,jridgewell/amphtml,cory-work/amphtml,danielrozenberg/amphtml,lannka/amphtml,zhouyx/amphtml,Gregable/amphtml,danielrozenberg/amphtml,lannka/amphtml,jpettitt/amphtml,voyagegroup/amphtml,prateekbh/amphtml,danielrozenberg/amphtml,honeybadgerdontcare/amphtml,adup-tech/amphtml,zhouyx/amphtml,rsimha-amp/amphtml,media-net/amphtml,sharethrough/amphtml,media-net/amphtml,media-net/amphtml,yandex-pcode/amphtml,taboola/amphtml,cory-work/amphtml,sharethrough/amphtml,alanorozco/amphtml,nexxtv/amphtml,honeybadgerdontcare/amphtml,mhc-gh/amphtml,nexxtv/amphtml,zhouyx/amphtml,alanorozco/amphtml,media-net/amphtml,Gregable/amphtml,jridgewell/amphtml,jmadler/amphtml,sharethrough/amphtml,danielrozenberg/amphtml,zhouyx/amphtml,jmadler/amphtml,prateekbh/amphtml,ampproject/amphtml,lannka/amphtml,yandex-pcode/amphtml,jridgewell/amphtml,nexxtv/amphtml,ampproject/amphtml,honeybadgerdontcare/amphtml,rsimha-amp/amphtml,smartadserver/amphtml,adup-tech/amphtml,rsimha-amp/amphtml,yandex-pcode/amphtml,jridgewell/amphtml,ampproject/amphtml,lannka/amphtml,mhc-gh/amphtml,adup-tech/amphtml,rsimha-amp/amphtml,yandex-pcode/amphtml,honeybadgerdontcare/amphtml,adup-tech/amphtml,Gregable/amphtml,zhouyx/amphtml,danielrozenberg/amphtml,prateekbh/amphtml,mhc-gh/amphtml,ampproject/amphtml,alanorozco/amphtml,nexxtv/amphtml,yandex-pcode/amphtml,Gregable/amphtml,yandex-pcode/amphtml,taboola/amphtml,taboola/amphtml,zhouyx/amphtml,voyagegroup/amphtml,jpettitt/amphtml,jpettitt/amphtml,jmadler/amphtml,voyagegroup/amphtml,danielrozenberg/amphtml,jpettitt/amphtml,media-net/amphtml,adup-tech/amphtml,honeybadgerdontcare/amphtml,rsimha-amp/amphtml,voyagegroup/amphtml,jridgewell/amphtml,cory-work/amphtml,alanorozco/amphtml,rsimha-amp/amphtml,alanorozco/amphtml,jmadler/amphtml,mhc-gh/amphtml,prateekbh/amphtml,smartadserver/amphtml,nexxtv/amphtml,ampproject/amphtml,lannka/amphtml,alanorozco/amphtml,prateekbh/amphtml,jpettitt/amphtml,sharethrough/amphtml,cory-work/amphtml,danielrozenberg/amphtml,jridgewell/amphtml,prateekbh/amphtml,smartadserver/amphtml,mhc-gh/amphtml,taboola/amphtml,cory-work/amphtml,jridgewell/amphtml,jpettitt/amphtml,jpettitt/amphtml,adup-tech/amphtml,lannka/amphtml,jpettitt/amphtml,mhc-gh/amphtml,smartadserver/amphtml,taboola/amphtml,voyagegroup/amphtml,lannka/amphtml,nexxtv/amphtml,zhouyx/amphtml,danielrozenberg/amphtml,alanorozco/amphtml,nexxtv/amphtml,jmadler/amphtml,Gregable/amphtml,sharethrough/amphtml,rsimha-amp/amphtml,sharethrough/amphtml,Gregable/amphtml,media-net/amphtml,ampproject/amphtml,jmadler/amphtml,taboola/amphtml,honeybadgerdontcare/amphtml,taboola/amphtml,ampproject/amphtml,Gregable/amphtml,cory-work/amphtml,smartadserver/amphtml,Gregable/amphtml,media-net/amphtml,cory-work/amphtml,ampproject/amphtml,smartadserver/amphtml