app: coverage floor (86) + framework-glue exclusions

Measured before choosing: 86.17%, identical via `mix test --cover` and via the exported sample + `mix test.coverage`, stable across seeds. Floor is the integer below that, with the rule written next to it: a FLOOR, ratcheted up as behavior-test yaks land, never lowered (a drop means the change or an exclusion is wrong). Exclusions are the modules the suite cannot or should not exercise, each justified in the config comment: `use`-generated glue (Repo, Mailer, Telemetry, ErrorHTML/ErrorJSON), the `use FirehoseWeb` macro, production release tasks (Release), the lib_dev credo check (NoConnShadowing), and test scaffolding (DataCase, ConnCase, AccountsFixtures, Test.FakeBlog). Everything else counts, CoreComponents/controllers/LiveViews included. Wiring matches blogex and the fast/push split: `test.coverage` runs the suite once with `--cover --export-coverage default` (deleting stale exports first, since `mix test.coverage` imports every .coverdata it finds and would pool them), then the `coverage` sensor enforces the floor from that export. The sensor guards on the export existing because `mix test.coverage` exits 0 when it finds nothing — a floor check that did not run must not pass.
2026-10-26 18:40:09 +00:00
parent 754c8fa1b9
commit abb712f8a2
2 changed files with 83 additions and 8 deletions
@@ -10,6 +10,7 @@ defmodule Firehose.MixProject do
      start_permanent: Mix.env() == :prod,
      aliases: aliases(),
      deps: deps(),
+      test_coverage: test_coverage(),
      compilers: [:phoenix_live_view] ++ Mix.compilers(),
      listeners: [Phoenix.CodeReloader]
    ]
@@ -99,4 +100,60 @@ defmodule Firehose.MixProject do
      precommit: ["compile --warning-as-errors", "deps.unlock --unused", "format", "test"]
    ]
  end
+
+  # The coverage floor the Lens pass enforces (`make verify` -> `make coverage`
+  # in app/). Rule: the threshold is a FLOOR. Raise it as behavior-test yaks
+  # land; never lower it. A drop means the change (or an exclusion) is wrong,
+  # not the floor.
+  #
+  # Measured 2026-10-26 (PostgreSQL on localhost:5432, exclusions below):
+  # 86.17%, identical via `mix test --cover` and via
+  # `mix test --cover --export-coverage default` + `mix test.coverage`, and
+  # stable across seeds. Floor is the integer below that.
+  #
+  # `test.coverage` deletes stale exports before sampling: `mix test.coverage`
+  # imports *every* .coverdata it finds, so leftover exports from earlier runs
+  # pool into the total and quietly inflate it.
+  #
+  # Excluded are modules the suite cannot or should not exercise; counting them
+  # would move the number without saying anything about app behavior:
+  #
+  #   * framework glue generated by `use`:
+  #       Firehose.Repo           `use Ecto.Repo`
+  #       Firehose.Mailer         `use Swoosh.Mailer`
+  #       FirehoseWeb.Telemetry   Phoenix's telemetry supervisor + metric list
+  #       FirehoseWeb.ErrorHTML   Phoenix error renderers, both delegating to
+  #       FirehoseWeb.ErrorJSON   Phoenix.Controller.status_message_from_template/1
+  #   * FirehoseWeb              the `use FirehoseWeb` macro: imports and aliases
+  #                              only, nothing that executes
+  #   * Firehose.Release         production release tasks (`mix ecto.migrate` on
+  #                              Dokku); the suite never runs them
+  #   * Firehose.Checks.NoConnShadowing
+  #                              lib_dev credo check, exercised by `mix credo`
+  #                              and not by tests
+  #   * test scaffolding         Firehose.DataCase, FirehoseWeb.ConnCase,
+  #                              Firehose.AccountsFixtures, Firehose.Test.FakeBlog:
+  #                              fixtures measure the tests, not the app
+  #
+  # Everything else counts — CoreComponents, controllers, LiveViews included:
+  # that is where the behavior-test work shows up as a higher floor.
+  defp test_coverage do
+    [
+      summary: [threshold: 86],
+      ignore_modules: [
+        Firehose.Repo,
+        Firehose.Mailer,
+        Firehose.Release,
+        FirehoseWeb,
+        FirehoseWeb.Telemetry,
+        FirehoseWeb.ErrorHTML,
+        FirehoseWeb.ErrorJSON,
+        Firehose.Checks.NoConnShadowing,
+        Firehose.DataCase,
+        FirehoseWeb.ConnCase,
+        Firehose.AccountsFixtures,
+        Firehose.Test.FakeBlog
+      ]
+    ]
+  end
 end