CI: backend tests on 4 workers, so the job finishes inside its timeout

.github/workflows/backend.yml

@@ -3,9 +3,10 @@ name: backend
 on:
   push:
     branches: [main]
-    paths: ["backend/**", ".github/workflows/backend.yml"]
+    # The tests build their database from the role scripts in infra/compose/postgres/initdb (tests/conftest.py)
+    paths: ["backend/**", "infra/compose/postgres/initdb/**", ".github/workflows/backend.yml"]
   pull_request:
-    paths: ["backend/**", ".github/workflows/backend.yml"]
+    paths: ["backend/**", "infra/compose/postgres/initdb/**", ".github/workflows/backend.yml"]
 
 concurrency:
   group: backend-${{ github.ref }}
@@ -17,7 +18,8 @@ permissions:
 jobs:
   checks:
     runs-on: ubuntu-24.04
-    timeout-minutes: 15
+    # 4,120 tests on 4 workers take about 7.5 minutes on a 4-CPU machine; this leaves room for a slower runner
+    timeout-minutes: 30
     defaults:
       run:
         working-directory: backend

backend/check.sh

@@ -6,4 +6,7 @@ uv run ruff check .
 uv run ruff format --check .
 uv run mypy
 uv run lint-imports
-uv run pytest "$@"
+# Four workers, each with its own PostgreSQL, Redis and object store containers (the session fixtures run
+# once per worker). The suite waits on the databases far more than on the CPU, so this fits the 4-vCPU CI
+# runner and a 4-CPU Colima. Pass -n 0 to run serially.
+uv run pytest -n 4 "$@"

backend/pyproject.toml

@@ -162,6 +162,7 @@ dev = [
     "pytest>=9.1.1",
     "pytest-asyncio>=1.4.0",
     "pytest-cov>=7.1.0",
+    "pytest-xdist>=3.8",
     "ruff>=0.16.9",
     "testcontainers[postgres,redis]>=4.15.0",
     "types-aiobotocore[s3]>=3.9.1",