Python Testing

Priority: P0 (CRITICAL)

[BE-TEST-01] Parametrized Tests for Equivalent Inputs: Prefer pytest.mark.parametrize for equivalent inputs and boundary permutations. Distinct scenarios may stay separate.
[BE-TEST-02] Ban on Brittle SQL String Matching: Test pure domain calculations directly or use fakes/testcontainers; do not regex-match SQL strings in mocks.
[BE-TEST-03] Ban on Shallow Assertions: Never assert only assert result without inspecting domain attributes and invariants.
[BE-TEST-04] Ban on Pass-Through Seam Mocks: Repositories and adapters must test contract compliance and error mapping; ban 1:1 pass-through mock echoing.
[BE-TEST-05] Bug-First Regression Lock: Every PR fixing a bug ticket or with title fix(...) must introduce a failing test reproducing the defect before fixing it.