4/5 refactor: extract within-group ordering out of algorithms#123
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vokracko wants to merge 4 commits intojerry-git:masterfrom
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4/5 refactor: extract within-group ordering out of algorithms#123vokracko wants to merge 4 commits intojerry-git:masterfrom
vokracko wants to merge 4 commits intojerry-git:masterfrom
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The previous setup relied on pytest-cov (``--cov pytest_split --cov tests`` in addopts) which has a long-standing limitation when measuring a pytest plugin: the plugin imports happen during pytest's plugin discovery, *before* pytest-cov starts tracing. Anything that runs at import time (class bodies, decorators, type aliases, enum definitions) is reported as uncovered even though it obviously executed - the plugin wouldn't load otherwise. The ``CoverageWarning: Module pytest_split was previously imported, but not measured`` made that explicit. The cookiecutter template the project was generated from worked around this by adding ``--cov tests`` to the addopts, inflating the denominator with 100%-covered test files so the average reached 90%. That pulled the number up but stopped reporting the actual source coverage. Switch to ``coverage run -m pytest`` followed by ``coverage report``. Running ``coverage`` from the outside means tracing starts before Python imports anything at all, so plugin import-time code is counted. Real source coverage jumps from ~74% to 99%; threshold goes from 90 to 95 to reflect that.
Tests previously asserted each TestGroup field separately (`first.selected`, `first.deselected`, `first.duration`). Consolidate to a single equality check against an expected TestGroup, with concrete values for every field rather than only ``selected``.
Tighten the algorithm contract so each one receives a single data argument: a dict mapping pytest items to their durations. Promote the helper that builds the dict to a public name (compute_durations) and inline the two helpers that only it used. The plugin builds the dict once and passes it to the algorithm. Algorithm bodies otherwise consume the same (item, duration) stream they did before, so behaviour is unchanged. Sets up follow-ups that separate group membership from within-group ordering.
Algorithms now own only group membership; the plugin owns the order in which selected/deselected items are emitted to pytest. LeastDurationAlgorithm drops the original_index bookkeeping. Its body collapses to a name + duration sort followed by the heap-based balanced assignment, with selected ending up in heap-pop order. The plugin's collection hook then rebuilds the chosen group's selected and deselected lists in pytest's collection order, keyed on nodeid. That's now the single source of truth for preserving collection order, so subsequent algorithm changes don't have to worry about it. End-to-end behaviour is unchanged: pytest still executes each group's tests in the order it collected them.
This was referenced Apr 29, 2026
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Fourth of five stacked PRs that fix #25.
Motivation. Today the algorithms own two responsibilities: what tests go in each group, and the order tests appear in within a group. Bundling those means the next PR (5/5) — which changes how membership is decided — has to be careful not to disturb ordering. Splitting them into separate concerns lets 5/5 focus purely on membership; the plugin owns within-group ordering for both algorithms via a single helper.
What changes.
LeastDurationAlgorithmdrops theoriginal_indexmachinery — its body collapses to a name + duration sort followed by the heap-based balanced assignment. The plugin's collection hook then rebuilds the chosen group via the newselect_in_collection_orderhelper.End-to-end behaviour is unchanged: pytest still runs each group's tests in collection order.
Stack.
coverage run→ 1/5 build: measure coverage on source only via coverage run #120TestGroupdirectly → 2/5 refactor: assert TestGroup directly in algorithm tests #121duration_based_chunks— closes Splits invalid when collection order not deterministic #25 → 5/5 fix: stabilise duration_based_chunks across collection orders #124