The document discusses test-driven development (TDD) and provides an opinionated definition and guidelines for TDD. It defines TDD as designing class responsibilities, writing an initial unit test, generating code stubs, ensuring the test fails, implementing the code, ensuring the test succeeds, identifying alternative scenarios, and repeating the process twice before refactoring. It also provides examples of code organization for TDD and recommends keeping tests focused on relevant parts of the code and avoiding debugger use. External resources on effective TDD practices are referenced.