Vibe Golden File Testing

vibe-golden-file-testing

Golden file tests are powerful but brittle. This skill makes them robust.

When to Use This Skill

• Implementing tests that compare output against saved expected output
• Tests that currently break because dates, timestamps, or IDs change
• API response testing with dynamic fields
• CLI output testing

When NOT to Use This Skill

• Simple unit tests with static assertions
• Tests where the exact output IS the requirement (byte-for-byte)
• Performance benchmarks

The Problem

Golden tests break when they contain:

• Dates/timestamps (2026-02-28 → different tomorrow)
• UUIDs/IDs (random each run)
• Hostnames/ports (different per environment)
• File paths (absolute paths differ per machine)
• Durations (took 1.23s → varies by machine)

Steps

1. Identify dynamic fields in the output being tested

1. Create normalizer function:

`` func normalizeOutput(s string) string { // Dates: 2026-02-28 → REDACTED_DATE s = dateRegex.ReplaceAll(s, "REDACTED_DATE") // UUIDs: 550e8400-... → REDACTED_UUID s = uuidRegex.ReplaceAll(s, "REDACTED_UUID") // Timestamps: 1709136000 → REDACTED_TS s = tsRegex.ReplaceAll(s, "REDACTED_TS") // Durations: 1.23s → REDACTED_DURATION s = durationRegex.ReplaceAll(s, "REDACTED_DURATION") return s } ``

1. Apply normalization to BOTH:

• The actual output (at test time)
• The golden file (at generation time)

1. Generate golden file with update flag:

`` if os.Getenv("UPDATE_GOLDEN") == "1" { os.WriteFile(goldenPath, normalized, 0644) } ``

1. Document update command:

`` # To update golden files: UPDATE_GOLDEN=1 go test ./... ``

Common Normalizations

| Pattern | Regex | Replacement | |---------|-------|-------------| | ISO Date | \d{4}-\d{2}-\d{2} | REDACTEDDATE | | ISO DateTime | \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2} | REDACTEDDATETIME | | UUID | [0-9a-f]{8}-[0-9a-f]{4}-... | REDACTEDUUID | | Unix timestamp | \b1[6-9]\d{8}\b | REDACTEDTS | | Duration | \d+\.?\d*[µnm]?s | REDACTEDDURATION | | Absolute path | /home/\w+/ or C:\\Users\\ | REDACTEDPATH | | Port | :\d{4,5}\b | :REDACTED_PORT |

Output Format

Golden File Setup: [Test Name]

Dynamic fields found: X Normalizations applied: Y Golden file: [path] Update command: UPDATE_GOLDEN=1 [test command]

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: ash1794
• Source: ash1794/vibe-engineering
• License: MIT

Install and usage instructions live in the source repository linked above.