test: add Test classes for the seven response models (#65)

[tschm]

Summary

Rhiza's check_test_layout requires every source class A to have a mirrored TestA. Seven response models had none, failing the gate.

Source	Models	Kind
api/interface.py	PlotResult, ServerStatus	TypedDict
api/routes.py	InitDataResponse, SessionInfo, SessionListResponse, DeleteSessionResponse, StatusResponse	BaseModel

Why mirroring rather than the opt-out

The issue offered a documented [tool.check_test_layout] enforce = false opt-out as the lighter option. I went the other way after reading the checker: enforce is all-or-nothing — there is no per-class exemption, only enforce, reason and exempt_dirs. Disabling it would also stop catching a genuinely missing test_<module>.py later, which is the part of the gate that currently passes and is worth keeping.

So the gate stays fully enforced.

The tests earn their place

They aren't schema tautologies — they pin contracts that can silently drift:

• PlotResult / ServerStatus key sets are asserted against what plot() and get_server_status() actually return, on both the success and validation-failure paths. A field added to one and not the other now fails.
• PlotResult.__total__ is False vs ServerStatus.__total__ is True documents why one type covers both success and failure shapes.
• SessionInfo and StatusResponse are validated against live /api/sessions and /api/status payloads.
• The BaseModel tests cover construction, required-field validation, nested coercion and the empty-listing case.

Style follows the existing TestDataResponse / TestErrorResponse classes.

Verification

$ check_test_layout.py
Test layout OK: tests mirror sources 1:1     (exit 0)

$ make test
172 passed  (154 -> 172, +18)  — Total coverage: 100.00%

Tests-only change — no src/ or behaviour touched.

Closes #65

[Copilot]

Pull request overview

Adds missing mirrored Test* classes for seven API response models so Rhiza’s check_test_layout gate passes while also asserting key aspects of the models’ runtime contracts.

Changes:

• Added TestInitDataResponse, TestSessionInfo, TestSessionListResponse, TestDeleteSessionResponse, and TestStatusResponse to cover BaseModel response schemas and validate against live endpoint payloads.
• Added TestPlotResult and TestServerStatus to cover TypedDict response contracts and compare declared keys vs real function outputs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/pycharting/api/test_routes.py	Adds mirrored tests for five BaseModel response models in api.routes, including endpoint-payload validation.
tests/pycharting/api/test_interface.py	Adds mirrored tests for two TypedDict response models in api.interface, checking declared keys and real return shapes.

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