Test Automation Pyramid
The test automation pyramid is a model for balancing test investment across levels — a large base of fast unit tests, a smaller middle layer of integration tests, and a thin top layer of slow, brittle end-to-end tests — favoring cheap, fast, reliable tests over slow, expensive ones wherever possible.
The shape encodes a cost tradeoff: unit tests are fast, cheap to write, and pinpoint failures precisely, so they should be the most numerous; end-to-end tests are slow, expensive to maintain, and vague about what actually broke when they fail, so they should be the fewest, reserved for the most critical user journeys only.
Teams that invert the pyramid — a thin base of unit tests and a huge suite of slow end-to-end tests, sometimes called an "ice cream cone" anti-pattern — typically end up with slow CI pipelines, flaky suites, and long feedback loops, which is exactly the failure mode the pyramid shape is meant to prevent.
