Produce test reports for test runs

These will help surface flaky tests, and help PR authors see what tests
are failing, if any. The workflow uses the really excellent [Publish
Test Results][ptr] GitHub action to do all the heavy lifting.

[ptr]: https://github.com/marketplace/actions/publish-test-results

.config/nextest.toml

@@ -6,6 +6,7 @@
 # - Call out every test as it finishes, including slow, skipped and flaky tests
 # - List failures again at the end.
 # - Run all tests even if some failed.
+# - Output test results in JUnit format.
 [profile.ci]
 # "retries" defines the number of times a test should be retried. If set to a
 # non-zero value, tests that succeed on a subsequent attempt will be marked as
@@ -32,6 +33,12 @@ failure-output = "immediate-final"
 # to false.
 fail-fast = false
 
+[profile.ci.junit]
+# Output a JUnit report into the given file inside 'store.dir/<profile-name>'.
+# The default value for store.dir is 'target/nextest', so the following file
+# is written to the target/nextest/ci/ directory.
+path = "junit.xml"
+
 # profile used in GitHub coverage runs
 # - lower retry count as a compromise between speed and resilience
 # - no fail-fast to at least keep coverage percentages accurate.

.github/workflows/coverage.yml

@@ -1,4 +1,4 @@
-name: Test build
+name: 'Test Coverage'
 
 on:
   push:

.github/workflows/test-report.yml

@@ -0,0 +1,71 @@
+# This workflow makes it possible to publish test reports without running into
+# permission issues when the test workflow was run from a fork or by Dependabot.
+#
+# The test workflow uploads a junit file per matrix target as an artifact, plus
+# the worflow events file, both of which this worfklow buids upon. Note that
+# the events file artifact, specifically, is expected to be named 'Event File'.
+#
+# See the [Publish Test Results action documentation][ptr] for more information.
+#
+# [ptr]: https://github.com/marketplace/actions/publish-test-results#support-fork-repositories-and-dependabot-branches
+
+name: 'Test Report'
+on:
+  workflow_run:
+    workflows: ['Test Build']
+    types:
+      - completed
+
+permissions: {}
+
+jobs:
+  test-results:
+    name: Test Results
+    runs-on: ubuntu-latest
+    if: github.event.workflow_run.conclusion != 'skipped'
+
+    permissions:
+      checks: write
+
+      # permission to comment on PRs
+      pull-requests: write
+
+      # permission to download artifacts
+      actions: read
+
+    steps:
+      - name: Download and extract artifacts
+        env:
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+        run: |
+            # Unzip all artifacts created by the triggering workflow into
+            # directories under an `artifacts/` directory.
+            # 
+            # This uses `gh api` to output the name and URL for each artifact as
+            # tab-separated lines, then uses `read` to take each name and URL
+            # and download those to named zip files, and finally extracting those
+            # zip files into directories with matching names.
+
+            mkdir -p artifacts && cd artifacts
+
+            # The artifacts URL from the *triggering* test workflow, not *this*
+            # workflow.
+            artifacts_url=${{ github.event.workflow_run.artifacts_url }}
+
+            gh api "$artifacts_url" -q '.artifacts[] | [.name, .archive_download_url] | @tsv' | while read artifact
+            do
+                IFS=$'\t' read name url <<< "$artifact"
+                gh api $url > "$name.zip"
+                unzip -d "$name" "$name.zip"
+            done
+
+      # Run the publisher. Note that it is given the 'Event File' artifact
+      # created by the test workflow so it has the *original* webhook payload
+      # to base its context on.
+      - name: Publish Test Results
+        uses: EnricoMi/publish-unit-test-result-action@v2
+        with:
+          commit: ${{ github.event.workflow_run.head_sha }}
+          event_file: artifacts/Event File/event.json
+          event_name: ${{ github.event.workflow_run.event }}
+          junit_files: "artifacts/**/*.xml"

.github/workflows/test.yml

@@ -1,4 +1,4 @@
-name: Test build
+name: 'Test Build'
 
 on:
   push:
@@ -106,3 +106,24 @@ jobs:
           command: nextest
           args:  run --workspace --target=${{ matrix.target }}
           use-cross: ${{ matrix.cross }}
+
+      # The test result artifacts are used by the test-report.yaml workflow.
+      - name: upload test results
+        uses: actions/upload-artifact@v3
+        if: ${{ !matrix.cross }}
+        with:
+          name: Test results (${{ matrix.target }})
+          path: target/nextest/ci/junit.xml
+
+  # the event file (containing the JSON payload for the webhook triggering this
+  # workflow) is needed to generate test result reports with the correct
+  # context. See the test-report.yaml workflow for details.
+  event_file:
+    name: "Event File"
+    runs-on: ubuntu-latest
+    steps:
+    - name: Upload
+      uses: actions/upload-artifact@v3
+      with:
+        name: Event File
+        path: ${{ github.event_path }}