- One quality measure of an abstraction is the complexity
ofits interface (ie API size).
- Another measure is the amount of state the abstraction
encapsulates.
The simplest abstraction of many interfaces is two methods:
The API is small, not complex and the amount of state is small, given that parameters are only set right before a call, all parameters are cleared after every call and no other state is retained. Yet it's clear to anyone that this isn't a good abstraction and that it doesn't result in an implementation that requires few unit tests. It requires an immense amount of documentation and allows a great many variations that yield bad/unexpected results.
Hence, good abstractions require few unit tests.
Abstractions don't have unit tests: implementations have unit tests. It's the size and complexity of the implementation made possible by the abstraction that matters.
That interface is certainly inconvenient to use, and potentially quite dangerous without a clearParameters().
It's not at all a rebuttal of the article, though. The article points out that the number of unit tests a design requires is larger for more complicated designs. An interface like yours would require no fewer tests than another interface exposing the same functionality using conventional function calls.
