Quantitative failure estimates for software systems are traditionally made at end of testing using software reliability growth modeling. A persistent problem with most kinds of failure estimation methods and models is the dependency on historical data. This paper presents a method for estimating the total amount of failures possible to provoke from a unit, without historical data dependency. The method combines the results from having several developers testing the same unit with capture-recapture models to create an estimate of “remaining” number of failures. The evaluation of the approach consists of two steps: first a pre-study where the tools and methods are tested in a large open source project, followed by an add-on to a project at a medium sized software company. The evaluation was a success. An estimate was created, and it can be used both as a quality gatekeeper for units and input to functional and system testing.