What do employers except for Web designer job profile? [on hold]

Not sure if I am asking this question in the right forum

I am a web designer currently searching for a job. I have really good portfolio and work experience and when applying for a job, almost everyone calls me for the interview. But I often fail in test projects (when they give you task to design at home). I provide high quality work and really trying hard, so I'm interested if there is something I miss

What do employers want to see in test project? Are there some things to keep in mind?