Verification chain

A verification chain is an ordered sequence of automated checks that generated software must pass before it is delivered, arranged cheapest first so that failures are caught by the fastest check that can catch them.

newc0’s chain has four stages in order: typecheck, then tests, then a production build, then a smoke test. Each is a wider net than the last and each is slower, which is what makes running the whole chain on every build affordable.

The stages catch different classes of problem, so none is redundant. Code that typechecks can fail its tests. Code that passes tests can fail to build. An application that builds can still fail to start. Removing any stage makes the remaining ones misleading rather than merely less thorough.

Measured on the marketing-site scaffold in a network-less sandbox, the chain took 37 seconds end to end: typecheck 4.2s, tests 4.3s, production build 24.0s, smoke test 3.9s. That is one scaffold under one set of conditions, not a statement about every build.

See also repair loop, which is what happens when a stage fails, and the verification page.