tl;dr:“The test pyramid is the canonical heuristic for guiding test suite evolution. It conveys a simple message - prefer more unit tests than integration tests, and prefer more integration tests than end-to-end tests. While useful, the test pyramid lacks the details you need as your test suite grows and you face challenging trade-offs. To scale your test suite, go beyond the test pyramid. The SMURF mnemonic is an easy way to remember the tradeoffs to consider when balancing your test suite.”