MZlearn

Testing the Untestable: Workers, WASM, and Shadow DOM

The sequel to the free DuckDB series: a test suite for code jsdom cannot run. Real browsers, real WebAssembly, real workers, deterministic fixtures, fake-timer proofs for a debounced query runner, and end-to-end checks that a database file survives a reload. Seven lessons, $5.

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Finish the lessons and do the challenges — if your build doesn't run, I'll debug it with you, and if we can't fix it, double your money back. The guarantee.

  1. Why jsdom Cannot Test This
  2. Deterministic Data
  3. The Worker Contract Against a Real Engine
  4. SQL You Can Trust
  5. The Query Runner Under Fake Timers
  6. Components, Shadow Roots, and updateComplete
  7. End to End, in a Real Browser

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