Writing the tests for FluentPath is a challenge. The library is a wrapper around a legacy API (System.IO) that wasn’t designed to be easily testable. If it were more testable, the sensible testing methodology would be to tell System.IO to act against a mock file system, which would enable me to verify that my code is doing the expected file system operations without having to manipulate the actual, physical file system: what we are testing here is FluentPath, not System.IO. Unfortunately, that is not an option as nothing in System.IO enables us to plug a mock file system in. As a consequence, we are left with few options. A few people have suggested me to abstract my calls to System.IO away so that I could tell FluentPath – not System.IO – to...