macios-ci-failure-inspector

name

macios-ci-failure-inspector

description

Investigate and triage CI failures for dotnet/macios from Azure DevOps build URLs. Use this skill whenever the user shares a DevOps build link, asks about CI failures, wants to understand why a build failed, or asks to investigate test failures on any platform (iOS, tvOS, macOS, Mac Catalyst). Also use when the user says things like "CI is red", "tests are failing", "build broke", or "what happened in CI".

macios CI Failure Inspector

Investigate Azure DevOps CI failures for the dotnet/macios repository, extract root causes, and report findings.

References

Read these as needed during investigation:

• references/azure-devops-cli.md — az CLI commands, artifact naming conventions, and JSON parsing caveats. Read this when you need to construct az commands or download artifacts.

Inputs

Collect from the user:

• Build URL — an Azure DevOps build results link, e.g. https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=<ID>&view=results
• Scope — whether to investigate only, or also attempt fixes (default: investigate only)

Extract the buildId from the URL query parameter.

Investigation workflow

Phase 1: Build overview

Fetch the build metadata to understand the big picture:

az pipelines build show --id <buildId> --org https://devdiv.visualstudio.com --project DevDiv -o json > /tmp/build_show.json

Extract from the output:

• result (succeeded, failed, partiallySucceeded, canceled)
• sourceBranch — what branch triggered the build
• definition.name — which pipeline ran
• triggerInfo or reason — what triggered it (PR, push, schedule)

If the build succeeded, tell the user and stop.

Phase 2: Timeline — identify failing jobs and tasks

The timeline gives you every job and task in the build with its result:

az devops invoke --area build --resource timeline --route-parameters project=DevDiv buildId=<buildId> --org https://devdiv.visualstudio.com -o json > /tmp/build_timeline.json

Parse the timeline to find failed records. Use Python for robust JSON parsing because az devops invoke output can include trailing non-JSON text:

import json

with open('/tmp/build_timeline.json', 'r') as f:
    content = f.read()
data = json.JSONDecoder().raw_decode(content)[0]

failed = [r for r in data.get('records', []) if r.get('result') == 'failed']
for r in failed:
    print(f"  [{r['type']}] {r['name']} (id={r['id']}, logId={r.get('log', {}).get('id', 'N/A')})")

Group failures into categories:

• Test failures — tasks named "Run tests" or jobs like T: monotouch_ios, T: monotouch_tvos, macOS tests
• Infrastructure failures — tasks like "Provision Xcode", "Reserve bot", setup tasks
• Build failures — compilation or packaging tasks

Phase 3: Download TestSummary artifacts (primary failure source)

The xharness test runner logs are 40K+ lines and don't contain standard NUnit failure patterns inline. TestSummary artifacts are the fastest and most reliable way to identify failures. Always start with these before digging into raw logs.

List all artifacts:

az pipelines runs artifact list --run-id <buildId> --org https://devdiv.visualstudio.com --project DevDiv -o json

Download TestSummary artifacts for each failing job. Each artifact must go to a separate directory to avoid overwriting (they all contain a file named TestSummary.md):

artifact="TestSummary-simulator_testsmonotouch_macos-1"
mkdir -p "/tmp/ci-artifacts/${artifact}"
az pipelines runs artifact download \
  --artifact-name "$artifact" \
  --path "/tmp/ci-artifacts/${artifact}" \
  --run-id <buildId> \
  --org https://devdiv.visualstudio.com --project DevDiv
cat "/tmp/ci-artifacts/${artifact}/TestSummary.md"

The TestSummary.md file contains a structured markdown report with:

• Count of passed/failed tests
• For each failure: test configuration name, failure type (BuildFailure, Failed, Crashed, TimedOut), and brief error message
• Build failures show the configuration variant (e.g. "monotouch-test/macOS/Debug (ARM64): BuildFailure")
• Test failures may include the failing test class and assertion message

Common artifact names map to timeline jobs:

• TestSummary-simulator_testsmonotouch_ios-1 → monotouch_ios
• TestSummary-simulator_testsmonotouch_tvos-1 → monotouch_tvos
• TestSummary-simulator_testsmonotouch_macos-1 → monotouch_macos
• TestSummary-simulator_testsmonotouch_maccatalyst-1 → monotouch_maccatalyst
• TestSummary-simulator_testsdotnettests_ios-1 → dotnettests_ios
• TestSummary-simulator_testsdotnettests_tvos-1 → dotnettests_tvos
• TestSummary-simulator_testsdotnettests_macos-1 → dotnettests_macos
• TestSummary-simulator_testsdotnettests_maccatalyst-1 → dotnettests_maccatalyst

Download these in parallel for all failing jobs to save time.

Phase 4: Get detailed test failure info from HtmlReport artifacts

For test failures (not build failures), download the corresponding HtmlReport artifact to get NUnit XML with exact test names, assertion messages, and stack traces:

artifact="HtmlReport-simulator_testsmonotouch_tvos-1"
mkdir -p "/tmp/ci-artifacts/${artifact}"
az pipelines runs artifact download \
  --artifact-name "$artifact" \
  --path "/tmp/ci-artifacts/${artifact}" \
  --run-id <buildId> \
  --org https://devdiv.visualstudio.com --project DevDiv
cd "/tmp/ci-artifacts/${artifact}" && unzip -o HtmlReport.zip -d htmlreport

Parse the NUnit XML files inside for specific test failures:

import xml.etree.ElementTree as ET
import glob

xml_files = glob.glob('htmlreport/tests/monotouch-test/*/test-ios-*.xml')
for xf in sorted(xml_files):
    tree = ET.parse(xf)
    for tc in tree.getroot().iter('test-case'):
        if tc.get('result') == 'Failed':
            fullname = tc.get('fullname', 'unknown')
            msg_el = tc.find('.//message')
            msg = msg_el.text[:200] if msg_el is not None and msg_el.text else ''
            trace_el = tc.find('.//stack-trace')
            trace = trace_el.text[:300] if trace_el is not None and trace_el.text else ''
            print(f"FAILED: {fullname}")
            print(f"  Message: {msg}")
            if trace:
                print(f"  Stack: {trace}")

Phase 5: Extract build error details from raw logs (for BuildFailure cases)

Only use raw task logs when TestSummary shows BuildFailure and you need the specific compiler/build error. The logs are typically 40K+ lines — search narrowly:

az devops invoke --area build --resource logs \
  --route-parameters project=DevDiv buildId=<buildId> logId=<logId> \
  --org https://devdiv.visualstudio.com -o json > /tmp/build_log.json

Parse and search for build errors only:

import json

with open('/tmp/build_log.json', 'r') as f:
    data = json.JSONDecoder().raw_decode(f.read())[0]
lines = data.get('value', [])

for i, line in enumerate(lines):
    s = line.strip()
    if ': error MSB' in s or ': error CS' in s or ': error NU' in s:
        print(f"L{i}: {s[:300]}")
    elif 'cannot execute tool' in s or 'MetalToolchain' in s:
        print(f"L{i}: {s[:300]}")
    elif 'Build FAILED' in s:
        print(f"L{i}: {s[:300]}")

The xharness summary section near the end of the log also provides a task-level overview. Search backwards from the end for Summary::

for i in range(len(lines)-1, -1, -1):
    if 'Summary:' in lines[i]:
        for j in range(i, min(len(lines), i+10)):
            print(lines[j].strip())
        break

This shows Executed N tasks, Succeeded: N, Failed: N, Crashed: N, etc.

Phase 6: Categorize and report

Group all findings by category and severity. Use this report structure:

## CI Failure Report — Build <buildId>

**Pipeline:** <pipeline-name>
**Branch:** <branch>
**Result:** <result>

### Failing Jobs

#### <Job Name> (logId: <id>)
- **Category:** Test failure | Infrastructure | Build error
- **Failing tests:**
  - `<TestClass.TestMethod>` — <assertion message>
  - ...
- **Root cause:** <concise explanation>

### Infrastructure Issues
- <any provisioning/bot/setup failures>

### Summary
- Total failing jobs: N
- Test failures: N (list unique test names)
- Infrastructure failures: N
- Recommended actions: ...

Troubleshooting the investigation

az devops invoke returns non-JSON output

The output can contain trailing text after the JSON object. Always use json.JSONDecoder().raw_decode() for parsing rather than json.loads().

Timeline has many records

Filter by result == 'failed' first. If you need to understand job hierarchy, use the parentId field to trace task → job → stage relationships.

Artifact download fails

Some artifacts may only be available for a limited time or may require specific permissions. If download fails, fall back to log-based analysis.

Multiple build URLs provided

Investigate each build independently but cross-reference failures — if the same test fails across multiple builds, it's likely a real regression rather than flakiness.