A Successful Test Says Nothing,

at least in the beginning. Executed tests are experiments where the initial hypothesis is "this does not work". Tests running successfully (thus disproving the hypothesis) do not make sure "this" always works, but they are able to say that:

• in this specific case
• following a specific set of rules and steps
• from what I can observe
• "this" looks like it has worked

This gives only a small bit of confidence other experiments will be successful as well, so the real value at first is in having your hypothesis confirmed and your test failing. You just need to act on it.