While these tests are accurate do not watch them develop! Give them a full 3 minutes before you look at them. The dye settles and then gets a secondary dye run that totally looks like it's going to be positive then just keeps going. I've been using these tests for years and despite myself I always watch them develop, they do this every time. Give it a full 3 minutes if you don't want to go through a rollercoaster of emotions.

Note the dye building up on the left

Then it runs across and looks like it's about to turn positive

Then it just keeps going