EvalView Tutorials

March 12, 2026 · View on GitHub

Hands-on guides for mastering EvalView's advanced features, including multi-reference goldens, CI/CD regression detection, diff status interpretation, parameter-level debugging, and migration from older workflows.

Tutorial 1: Handling Non-Deterministic Agents with Multi-Reference Goldens

The Problem

Your LLM-based agent produces valid but varied outputs:

Run 1: "AAPL stock is \$150.23"
Run 2: "Apple Inc (AAPL) trades at \$150.23"
Run 3: "Current AAPL price: \$150.23"

All are correct, but evalview check fails because they don't match exactly.

The Solution: Multi-Reference Goldens

Save multiple acceptable variants as golden baselines.

Step 1: Create your first snapshot

evalview snapshot
# ✅ Snapshotted: stock-price-check

Step 2: Run again and save the variant

evalview run --save-golden result.json --variant variant1

Or use the simpler workflow:

evalview snapshot --variant variant1

Step 3: Repeat for variant 2

evalview snapshot --variant variant2

Step 4: Check matches ANY variant

evalview check
# ✅ Matched variant 2/3

How Multi-Reference Works

Compare against ALL variants - Check runs your test against default + all variants
Return best match - Passes if ANY variant matches (ranked by severity)
Up to 5 variants - Prevents storage bloat
Severity ranking: PASSED > OUTPUT_CHANGED > TOOLS_CHANGED > REGRESSION

When to Use Variants

✅ Good use cases:

LLM output with acceptable creative variation
Tools called in different but valid orders
Equivalent responses with different wording

❌ Bad use cases:

Unstable/flaky agents (fix the agent instead)
Widely different behaviors (split into separate tests)
5 variants needed (test is too broad)

Managing Variants

# List all variants
evalview golden list

# Delete a variant
evalview golden delete stock-price-check --variant variant1

# Show variant count
evalview golden list  # Shows "stock-price-check (3 variants)"

Tutorial 2: Setting Up Regression Detection in GitHub Actions

Goal

Automatically catch agent regressions in CI before they reach production.

Step 1: Create Baseline

On your main branch:

evalview snapshot
git add .evalview/golden/
git commit -m "Add golden baselines for agent tests"
git push

Step 2: GitHub Actions Workflow

Create .github/workflows/agent-regression-check.yml:

name: Agent Regression Check
on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  regression-check:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: '3.9'

      - name: Install dependencies
        run: |
          pip install evalview
          # Install your agent dependencies
          pip install -r requirements.txt

      - name: Run regression check
        run: evalview check --fail-on REGRESSION --json
        env:
          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}

      - name: Upload results
        if: always()
        uses: actions/upload-artifact@v3
        with:
          name: regression-check-results
          path: .evalview/results/

Step 3: Configure Exit Codes

Choose what failures should block PRs:

Strict mode (fail on any change):

run: evalview check --strict

Selective (fail only on score regressions):

run: evalview check --fail-on REGRESSION

Permissive (fail on regressions + tool changes):

run: evalview check --fail-on REGRESSION,TOOLS_CHANGED

Step 4: PR Comments (Optional)

Add diff summary to PR comments:

      - name: Parse results
        if: failure()
        id: parse
        run: |
          SUMMARY=$(evalview check --json | jq -r '.summary')
          echo "summary=$SUMMARY" >> $GITHUB_OUTPUT

      - name: Comment PR
        if: failure() && github.event_name == 'pull_request'
        uses: actions/github-script@v6
        with:
          script: |
            github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: '⚠️ **Agent Regression Detected**\n\n${{ steps.parse.outputs.summary }}'
            })

Advanced: Parallel Test Matrix

Run multiple agent configurations:

strategy:
  matrix:
    model: [gpt-4, claude-3-sonnet]
    agent_config: [default, verbose]

steps:
  - name: Run regression check
    run: evalview check --config ${{ matrix.model }}-${{ matrix.agent_config }}.yaml

Tutorial 3: Understanding Diff Statuses

The 4 Diff Statuses

EvalView uses structured diff statuses to categorize changes.

✅ PASSED

Meaning: Behavior matches baseline exactly.

What it shows:

Diff Summary
  5/5 unchanged

Action: Ship with confidence.

~ OUTPUT_CHANGED

Meaning: Tools and sequence correct, but output text differs.

What it shows:

⚠ OUTPUT_CHANGED: customer-support
  Output similarity: 82%
  Same tools, different wording

Common causes:

LLM creativity/temperature
Timestamp/date changes
Minor wording variations

Action:

Review output quality
If acceptable: evalview snapshot to update baseline
If unacceptable: Fix prompt and re-check

⚠️ TOOLS_CHANGED

Meaning: Agent called different tools or different order.

What it shows:

⚠ TOOLS_CHANGED: stock-analysis
  + web_search (new tool used)
  - calculator (no longer used)

Common causes:

Agent found alternative solution path
Tool availability changed
Prompt changes affected tool selection

Action:

Verify new tools produce correct results
Check if old tool was necessary
Update baseline if change is intentional

❌ REGRESSION

Meaning: Score dropped significantly (default: >5 points).

What it shows:

✗ REGRESSION: data-analysis
  Score: 88 → 71 (-17 points)
  Tool sequence differs
  Output quality degraded

Common causes:

Broken tools/dependencies
Model degradation
Prompt engineering gone wrong
Test data changed

Action:

Do not merge - Fix the issue
Investigate which component broke
Run evalview check after each fix attempt

Configuring Thresholds

Customize what triggers each status in .evalview/config.yaml:

diff:
  tool_similarity_threshold: 0.8      # Lower = stricter tool matching
  output_similarity_threshold: 0.9    # Lower = stricter output matching
  score_regression_threshold: 5.0     # Points drop before REGRESSION

Or per-test:

# tests/test-cases/my-test.yaml
name: flaky-llm-test
adapter_config:
  sequence_mode: "unordered"  # Don't care about tool order

expected:
  min_score: 75
  tools: ["search", "analyze"]

# Custom diff thresholds for this test only
diff_config:
  output_similarity_threshold: 0.85  # More lenient for this test

Tutorial 4: Parameter-Level Debugging

The Problem

Check says "TOOLS_CHANGED" but you don't know WHY.

Before parameter diffing:

⚠ TOOLS_CHANGED: search-analysis
  Tool: search (changed)

The Solution: Parameter Diffing

After parameter diffing:

⚠ TOOLS_CHANGED: search-analysis
  Tool: search (changed)
    Parameter differences:
      ~ query:
        golden: "AAPL stock price"
        actual: "AAPL current price"
        similarity: 76%
      - max_results: 10
      + limit: 5

Reading Parameter Diffs

Symbol meanings:

Symbol	Meaning	Example
`~`	Value changed	`query: "old" → "new"`
`-`	Parameter removed	`- max_results: 10`
`+`	Parameter added	`+ limit: 5`
(none)	Type changed	`id: "123" → 123`

Similarity percentage:

90-100%: Nearly identical (typo, minor change)
70-89%: Similar (wording variation)
50-69%: Moderately different
0-49%: Substantially different

Example: Debugging a Regression

$ evalview check

⚠ TOOLS_CHANGED: stock-search
  Tool: search (changed)
    Parameter differences:
      ~ query:
        golden: "AAPL stock price today"
        actual: ""
        similarity: 0%

Analysis: Query is empty! This is likely a bug.

Fix: Check your prompt or query construction logic.

Tutorial 5: Customizing Celebration Milestones

Default Milestones

Out of the box, EvalView celebrates:

3 checks: "You're on a roll"
5 checks: Panel with border
10 checks: ASCII art + "Reliability Champion"
25 checks: "Legendary" + shareable badge
50+ checks: "Incredible" milestone

Milestone Constants

Defined in evalview/core/celebrations.py:

STREAK_1 = 1
STREAK_3 = 3
STREAK_5 = 5
STREAK_10 = 10
STREAK_25 = 25
STREAK_50 = 50

Viewing Your Progress

$ evalview check

🔍 Comparing against your baseline...
✨ All clean! No regressions detected.

🎯 5 clean checks in a row! You're on a roll.

🟢 Project Health: 100%
  Total checks: 5
  Clean: 5
  Regressions: 0
  Current streak: 5 🔥
  Best streak: 5

Streak Tracking Data

Stored in .evalview/state.json:

{
  "current_streak": 5,
  "longest_streak": 10,
  "total_checks": 25,
  "regression_count": 3,
  "milestones_hit": ["streak_3", "streak_5", "streak_10"]
}

Note: This file is personal (not committed to git).

Tutorial 6: Migrating from `run --diff` to `snapshot/check`

Old Workflow

evalview run --save-golden result.json
# ... make changes ...
evalview run --diff

Pain points:

Have to remember result file path
Verbose output
Not memorable

New Workflow

evalview snapshot
# ... make changes ...
evalview check

Benefits:

No file paths to remember
Concise, diff-focused output
Habit-forming streak tracking
Celebratory feedback

Migration Guide

Step 1: If you have existing golden files, they still work:

# Your old goldens in .evalview/golden/ are compatible
evalview check  # Works immediately

Step 2: Update your CI:

- evalview run --diff --fail-on REGRESSION
+ evalview check --fail-on REGRESSION --json

Step 3: Update your docs/README:

- To create baseline: evalview run --save-golden
+ To create baseline: evalview snapshot

- To check for regressions: evalview run --diff
+ To check for regressions: evalview check

Backward Compatibility

Both workflows coexist:

# Old way still works
evalview run --save-golden
evalview run --diff

# New way (recommended)
evalview snapshot
evalview check

Tutorial 7: Interpreting Reason Codes

What are Reason Codes?

Structured, machine-readable error codes with remediation guidance.

Example

$ evalview check

Failure Reasons:
  ✗ TOOL_MISSING: Expected tool 'calculator' was not called
    → Fix: Ensure your agent has access to 'calculator' and the query triggers its use

  ⚠ PARAM_VALUE_CHANGED: search.query changed
    Details: {"expected": "AAPL stock", "actual": "AAPL"}
    → Fix: Update test case if this is intentional

Common Reason Codes

Code	Severity	Meaning	Fix
`TOOL_MISSING`	error	Expected tool not called	Check agent tool access
`TOOL_UNEXPECTED`	info	Agent called extra tool	Add to test if correct
`TOOL_NAME_MISMATCH`	warning	Case/naming difference	Update test case name
`SEQUENCE_LENGTH_MISMATCH`	error	Wrong number of tools	Check agent logic
`SEQUENCE_ORDER_VIOLATION`	error	Tools out of order	Use `sequence_mode: unordered` if order doesn't matter
`PARAM_VALUE_CHANGED`	warning	Parameter value differs	Review and snapshot if OK
`PARAM_TYPE_MISMATCH`	error	Parameter type changed	Check serialization

Using Reason Codes in CI

evalview check --json | jq '.diffs[].reason_codes'

Output:

[
  {
    "code": "TOOL_MISSING",
    "severity": "error",
    "message": "Expected tool 'search' was not called",
    "context": {
      "expected_tool": "search",
      "actual_tools": ["analyze"]
    },
    "remediation": "Ensure your agent has access to 'search'"
  }
]

Next Steps

More examples: See examples/ directory
API Reference: Coming soon
Community: GitHub Discussions for questions
Contributing: See CONTRIBUTING.md

Getting Started — Install EvalView and run your first test
Golden Traces — How snapshot and check work
Evaluation Metrics — Scoring methodology
CI/CD Integration — Running regression checks in CI
Statistical Mode — pass@k for non-deterministic agents
CLI Reference — All commands and flags

Questions? Open an issue or discussion on GitHub!