A 'ball of mud' codebase is too complex to understand and its changes have unpredictable results, requiring a different approach like testing to solve.
Simple system tests running frequently in CI can confirm infrastructure is operational, which is a critical first step before tackling code correctness.
Start by adding two unit tests per work item to gradually build the team's testing skills and integrate testing into the development process.
The 'unit' in a unit test for a ball of mud is the smallest testable group of code, which reveals the actual system design, not an idealized one.
Mocking can ease the pain of dependencies but risks creating a shadow implementation; isolating dependencies by design is a more robust alternative.
Old, failing tests should be deleted, and new tests must be independent to avoid creating a debugging nightmare where test order affects outcomes.
Enforce test independence by running tests in a random order and optimize speed by decoupling code from frameworks, not just through parallelization.
Once infrastructure and unit tests are in place, add smoke tests for critical use cases to verify high-level application correctness.
The talk concludes by summarizing the need for a different approach to legacy code, followed by a Q&A on singletons, snapshot testing, and parameterized tests.
43:07Golo Roden
47:22Christian Kühn
56:49Jens Happe
26:33Annelore Egger
28:12Luise Freese
45:43Gil Zilberfeld
26:02Vincent Hennig & Anupam Krishnamurthy
24:38Carola Lilienthal
Jobs that call for the skills explored in this talk.
Think-cell
Foster City, United States of America
Peter Park System GmbH
München, Germany
Saby New Compy
Karlsruhe, Germany
CONTIAMO GMBH
Berlin, Germany