One size does not fit all. Testing strategies serve one purpose - to prevent and fix bugs earlier in the development process. While they can also document your code and provide other additional benefits - fixing and preventing bugs must be their number one goal. Whatever strategy fits your project, your team, and your code base - and fulfills that goal - is a good strategy. The core of any good Rails testing strategy is Better Specs and The Agile Test Pyramid.
Finally, tests must be written to be re-written. Business requirements will change. Code architecture will change. Variables will be renamed. Your tests should enable and embolden these changes, not prohibit and prevent them.
"All is flux." - Heraclitus