test: expand mutmut coverage to all files in src/flameconnect

[Copilot]

paths_to_mutate in setup.cfg only listed 4 files, silently excluding cli.py, const.py, exceptions.py, models.py, and the entire tui/ subdirectory (13 files) from mutation testing.

Changes

Expand mutation coverage

Replace the explicit file list with the package directory so mutmut discovers all Python files automatically:

# Before
[mutmut]
paths_to_mutate =
    src/flameconnect/protocol.py
    src/flameconnect/client.py
    src/flameconnect/auth.py
    src/flameconnect/b2c_login.py

# After
[mutmut]
paths_to_mutate = src/flameconnect

Fix test compatibility with mutmut

Remove the overly-aggressive builtins.__import__ patch from test_tui_import_error — sys.modules["flameconnect.tui"] = None alone is sufficient to trigger ImportError, and the blanket import patch was breaking mutmut's coverage tracking during the stats phase.

Speed up mutmut runtime

The expanded coverage increased mutmut runtime to ~35 minutes. Three optimizations were added to reduce this:

• --max-children 4 (was 2) in CI — GitHub Actions ubuntu-24.04 runners have 4 vCPUs
• do_not_mutate — excludes */__init__.py, const.py, and exceptions.py (re-exports, constants, and trivial class declarations that don't benefit from mutation testing), reducing from 23 to 19 mutated files
• max_stack_depth = 8 — limits how deep mutmut traces call stacks when mapping tests to mutants, speeding up the stats/mapping phase

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[deviantintegral]

@copilot Can you investigate and fix the test error in the CI job?

[Copilot]

@copilot Can you investigate and fix the test error in the CI job?

The CI failure was in test_tui_import_error during mutmut's stats phase. The test blanket-patched builtins.__import__ with side_effect=ImportError("no tui"), which blocked ALL imports — this broke mutmut's coverage tracking that runs during the stats collection.

The fix in c4af6e3 removes the builtins.__import__ patch since patch.dict("sys.modules", {"flameconnect.tui": None}) alone is sufficient to trigger ImportError when from flameconnect.tui import run_tui executes. All 1048 tests pass locally.

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[deviantintegral]

@copilot mutmut is taking ~35 minutes to run. That seems much slower than other mutation testing systems I've used given the size of this project. Is there anything that can be done to speed things up?

[Copilot]

@copilot mutmut is taking ~35 minutes to run. That seems much slower than other mutation testing systems I've used given the size of this project. Is there anything that can be done to...

Applied three optimizations in 77e5868:

1. --max-children 4 (was 2) — ubuntu-24.04 runners have 4 vCPUs, so this doubles parallelism
2. do_not_mutate — excludes */__init__.py, const.py, and exceptions.py (re-exports, constants, and trivial class declarations that don't benefit from mutation testing). Reduces from 23 to 19 mutated files.
3. max_stack_depth = 8 — limits how deep mutmut traces call stacks when mapping tests to mutants, speeding up the stats/mapping phase

These should roughly halve the runtime. If it's still too slow, the next lever would be mutate_only_covered_lines = true which uses coverage data to skip mutating uncovered lines entirely.