Trialing a change in assessment

One of the issues I've struggled with for a while is assessment. How do I assess 120 students in a way that's fair, consistent and useful? Several times I have gotten to the end of marking a test and thought 'Well that was a waste of time'.
So I decided to start researching some better methods. A blog that I love is that of Dan Meyer and he has some great concepts surrounding assessment. A blog entry I found of his (http://blog.mrmeyer.com/?p=5597) along with reading from clicking links in comments lead me to trial a new style of assessment in my current unit.
The traditional assessment for the chemistry unit I am taking is to have an end of unit test with perhaps a mid-way test. The issues I see with this method are forcing students to perform in a tiny pressure filled window, it usually tests for naming skills, and it doesn't allow for students to demonstrate progress.
The method I'm using is that of a series of 'mini tests'.
Mini test 1 was a surprise so you can imagine how popular that was! But this allowed me to have a discussion about the purpose of these tests. Students were given around 10 minutes to complete the test to the best of their abilities. The then had to self mark their test in a different colour and grade their performance on the back of the sheet. These test sheets are to remain in student's books as a reference and I collect a copy of their results.
Students then have a chance to reflect on their progress and review work. They get a chance to learn based on what they struggled with. This means they can focus on areas that are specific to them, it's not a one size fits all lesson, it's designed to be functional with all levels of ability and progress.
Mini test 2 is designed to follow a few lessons later and give a chance to show development. The students can improve their scores, showing me that they understand concepts now that earlier they struggled with. This means that the pressure to perform instantly is removed and effort/progress is rewarded. It also gives me instant feedback on how my lessons are progressing.

Having only done one test so far it is a bit too early to tell if it's going to be a keeper in the long run, but it is looking promising.