Let f(x) be a certain cryptographic function and let g, g: Im(f) → {true, false}, be an integrity test saying whether a particular value of f(x) fits into predefined integrity boundaries or not. The “Test and Repeat” paradigm is then characterized by the following pseudocode: repeat let y = f(x) until g(y) = true. On a first look, it may seem like a kind of best programming practice that can only improve overall security of the module. Especially, an architect can see it as a rather strong countermeasure against attacks based on computational faults – so called fault attacks. In this article, however, we will show that such a practice can induce particular cryptographic weaknesses. Therefore, it cannot be regarded as a general security improvement. Especially, it can even increase a vulnerability to the fault attacks. Its usage in cryptographic modules shall, therefore, undergo a proper cryptanalysis before being actually deployed.