I find this article misleading; with a biased PoV. The author says "empirical evidence is missing", yet advocates a testing methodology, banking largely on articles and PoVs of other individuals. Is there any software project the author would like to quote as a case-study? Is there any evidence to prove that the Lean method is better OR, the definition of what is better?

It is OK to be economical in what one would see as a cost of testing a product end-to-end. Call it whatever term you like, but functionally testing a product end-to-end has always followed an economical approach, as all such testing is a factor of time & resources. You'd perhaps be less economical if you were testing life-safety systems, but you could choose to be more economical if you considered your software to be not-that-critical, or, you needn't have to set exceptionally high standards.

I find it extremely odd that unittests are even considered into this equation of 'testing-costs', despite decades of improvements in software development processes. Unittests should be part of 'core' engineering & a part of development. Not a task that's added to testing costs. If you aren't writing unittests (irrespective of whether its TDD or not), you are not developing/engineering your product right. You are only building a stack of cards _hoping_ that it wouldn't collapse at some point in the future.

It's a sad state of affairs if one gives code 1st level treatment, but treats unittests, documentation, build scripts and other support infra as something less important; worth economizing. This is really what _matters_ when it comes to overall quality of a software.

One must remember that software is always improved, refactored, expanded, ported or worked on in some way or another. When unittests are missing, then the very boundaries that were meant to dictate the rules of the software don't apply anymore. This leads to human errors causing portions of software to break.

Critical pieces of software that exist today, exist strongly because they were engineered right (Linux kernel for example). Not because their developers followed an _economical_ approach to testing. If an OS disto claimed to perform economical end-to-end testing (of a potential user's most commonly performed paths), would the author of this article want to use that OS over one that has had strong ground-up unittests and testing of interfaces where they matter?