Extract a class from a bloated service
Apply Extract Class to separate a coherent responsibility from a large service.
InvoiceService has five reasons to change, and invoice numbering tests require email, PDF, and ledger setup. Extract Class: move a cohesive responsibility behind a focused API while preserving behavior. The common trap is extracting helper methods randomly because the class is large, leaving the same mixed reasons to change spread across more files. Find the cluster Group methods and fields that serve invoice numbering: prefix lookup, sequence formatting, fiscal-year reset, and duplicate check. This cluster has one change owner: finance operations. It does not need email or PDF behavior. Protect behavior Add characterization tests for current numbers: ACME-2026-0007, fiscal reset,…
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