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• Write description: This skill should be used when the user asks about "test validation", "assertion strategies", "regex vs contains", "handling flaky tests", "validation failures", "expected vs actual", or needs guidance on choosing validation approaches and handling edge cases. name: validation-strategies version: 1.0.0

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<!-- BEGIN MNEMONIC PROTOCOL -->

Memory

Search first: /mnemonic:search {relevant_keywords} Capture after: /mnemonic:capture {namespace} "{title}"

Run /mnemonic:list --namespaces to see available namespaces from loaded ontologies.

<!-- END MNEMONIC PROTOCOL -->

Validation Strategies

Choose and implement effective validation strategies for hook-driven tests.

Mnemonic Integration

Before advising on validation, check mnemonic for insights:

# Search for validation-related memories
rg -i "validation|assertion|regex|contains|flaky" ~/.claude/mnemonic/ ./.claude/mnemonic/ --glob "*.memory.md" -l | head -5

# Check learnings for validation experiences
rg -l "." ~/.claude/mnemonic/*/learnings/ --glob "*.memory.md" 2>/dev/null | xargs grep -l -i "validation\|expect" 2>/dev/null | head -5

Apply recalled insights:

• Validation approaches that worked well
• Flaky test patterns to avoid
• Regex patterns that proved reliable
• User's preferred validation strategies

Validation Approaches

String Matching (contains)

Strengths:

• Simple and readable
• Tolerant of formatting changes
• Fast execution

Weaknesses:

• May match unintended content
• No structure awareness
• Case-sensitive by default

Best for:

• Success/error messages
• UI text validation
• Presence checks

expect:
  - contains: "Operation successful"
  - contains: "Created"

Negative Matching (not_contains)

Strengths:

• Clear failure detection
• Complements positive checks
• Security validation

Weaknesses:

• Can't validate what IS present
• May miss variant error messages

Best for:

• Error absence verification
• Security checks (no sensitive data)
• Deprecation validation

expect:
  - not_contains: "error"
  - not_contains: "exception"
  - not_contains: "password"

Pattern Matching (regex)

Strengths:

• Precise structure validation
• Value extraction capability
• Multiple value matching

Weaknesses:

• Complex to write correctly
• Harder to debug failures
• Performance overhead

Best for:

• ID/UUID validation
• Numeric output
• Structured data
• Variable capture

expect:
  - regex: "ID:\\s+[a-f0-9]{12}"
  - regex: "Count:\\s+\\d+"
  - regex: "(success|complete|done)"

Choosing the Right Strategy

Decision Matrix

Scenario	Recommended	Why
Check operation succeeded	contains	Flexible message matching
Verify no errors	not_contains	Catches error variants
Extract ID for later use	regex with capture	Structured extraction
Validate numeric output	regex	Pattern precision
Check multiple valid responses	regex with alternation	(opt1|opt2)
Verify exact format	regex	Full control

Combination Strategies

Use multiple expectations for robust validation:

expect:
  # Positive confirmation
  - contains: "Memory created"
  # Negative confirmation
  - not_contains: "error"
  - not_contains: "failed"
  # Structured validation
  - regex: "ID:\\s+([a-f0-9]+)"

Regex Patterns Reference

Common Patterns

Pattern	Matches	Use Case
\\d+	One or more digits	Counts, IDs
[a-f0-9]+	Hex string	UUIDs, hashes
\\w+	Word characters	Identifiers
.*	Anything (greedy)	Flexible matching
.*?	Anything (non-greedy)	Minimal matching
\\s+	Whitespace	Flexible spacing
(a|b|c)	Alternation	Multiple valid values

ID Patterns

# UUID v4
regex: "[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}"

# Short ID (12 hex chars)
regex: "[a-f0-9]{12}"

# Numeric ID
regex: "ID:\\s+(\\d+)"

# Alphanumeric ID
regex: "ID:\\s+([a-zA-Z0-9]+)"

Output Patterns

# Success with count
regex: "Found\\s+(\\d+)\\s+results"

# Status messages
regex: "Status:\\s+(active|inactive|pending)"

# Version numbers
regex: "v(\\d+\\.\\d+\\.\\d+)"

# Timestamps
regex: "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}"

Handling Edge Cases

Empty Results

Validate empty states explicitly:

- id: search_no_results
  action: "Search for 'nonexistent_term_xyz'"
  expect:
    - regex: "(no results|0 found|empty)"
    - not_contains: "error"

Variable Output

Handle outputs that may vary:

expect:
  # Accept range of counts
  - regex: "Found\\s+[1-9]\\d*\\s+results"
  # Accept multiple success messages
  - regex: "(created|updated|saved)"

Whitespace Sensitivity

Use \s+ for flexible whitespace:

# Rigid (may fail)
- contains: "ID: abc123"

# Flexible (handles formatting)
- regex: "ID:\\s+abc123"

Case Sensitivity

Regex can handle case variations:

# Case-insensitive with (?i)
- regex: "(?i)success"

# Explicit alternatives
- regex: "(Success|SUCCESS|success)"

Handling Flaky Tests

Causes of Flakiness

1. Timing issues: Async operations not complete
2. Order dependence: Tests affect each other
3. External dependencies: Network, services
4. Non-deterministic output: Timestamps, random IDs

Mitigation Strategies

1. Flexible expectations:

expect:
  # Don't match exact timestamp
  - regex: "Created at: \\d{4}-\\d{2}-\\d{2}"
  # Don't match exact ID
  - regex: "ID:\\s+[a-f0-9]+"

2. Retry logic (in runner):

cmd_validate_with_retry() {
  local max_retries=3
  for i in $(seq 1 $max_retries); do
    if cmd_validate "$1"; then
      return 0
    fi
    sleep 1
  done
  return 1
}

3. Tag flaky tests:

- id: external_api_test
  tags: [flaky, external]

4. Isolate stateful tests:

- id: cleanup_before_test
  action: "Reset test state"
  tags: [setup]

- id: actual_test
  depends_on: cleanup_before_test

Debugging Validation Failures

Reading Failure Messages

❌ FAIL: search_basic
Failures:
  - Missing: 'results found'
  - Pattern not found: 'Count:\s+\d+'

Interpretation:

• Missing: 'X' → contains: X failed
• Unexpected: 'X' → not_contains: X failed
• Pattern not found: 'X' → regex: X failed

Troubleshooting Steps

1. Get actual response: Check what Claude returned
2. Compare expectations: Look for typos, case issues
3. Test regex separately: Use online regex tester
4. Simplify expectations: Start broad, narrow down
5. Check for invisible chars: Whitespace, newlines

Common Fixes

Symptom	Likely Cause	Fix
Contains fails on visible text	Case mismatch	Use regex with (?i)
Regex fails on structured output	Escaping issue	Double-escape special chars
Intermittent failures	Timing/async	Add flexible patterns
All tests fail	State corruption	Reset with /run-tests --reset

Additional Resources

Reference Files

• references/validation-approaches.md - Validation strategies and patterns