Backend Testing Agent - Best Practices and Advice

Purpose: Guidance for using the backend comprehensive testing agent effectively

Related Files:

.claude/commands/backend-testing.md - Agent command and methodology
ENDPOINT-WORK-ADVICE.md - OpenAPI generation patterns and troubleshooting
VALIDATE-DATA-PERSISTENCE-ADVICE.md - DynamoDB verification patterns
TEST-ORCHESTRATION-ADVICE.md - Multi-layer testing coordination

Overview

The backend testing agent provides comprehensive REST API testing with:

OpenAPI specification validation
Edge case testing (25+ per field)
DynamoDB persistence verification
Intelligent error classification
Automatic test cleanup
Integration with root-cause-analyst for "not implemented" errors

When to Use Backend Testing Agent

Primary Use Cases

1. New Feature Development

After implementing backend endpoint
Before frontend integration
To validate OpenAPI spec completeness
To discover edge case handling gaps

2. OpenAPI Specification Changes

After adding/modifying endpoints
After changing field validation rules
After updating data models
To verify spec-implementation alignment

3. Bug Validation

To reproduce reported backend issues
To verify bug fixes don't introduce regressions
To validate edge cases after fixes

4. Pre-Deployment Validation

Complete backend endpoint testing
OpenAPI specification completeness check
DynamoDB persistence verification
Edge case handling validation

Integration Points

Works With:

test-orchestrator - Delegates backend testing
frontend-comprehensive-testing - Backend health validation
backend-architect - Reports findings and recommendations
root-cause-analyst - Investigates "not implemented" errors
feature-documentation - Updates docs with validated behavior

Input From:

backend/api/openapi_spec.yaml - API specification
claudedocs/features/*/backend/ - Feature documentation
backend/api/src/main/python/openapi_server/impl/ - Implementation code

Output To:

claudedocs/testing/backend/ - Test reports
Teams channel - Test result notifications
Feature documentation - Validated edge cases

Best Practices

OpenAPI Specification Validation

DO:

✅ Validate OpenAPI spec BEFORE testing endpoints
✅ Report missing validations as bugs with severity
✅ Test reasonable boundaries even if spec incomplete
✅ Document assumptions made when spec unclear
✅ Recommend specific OpenAPI constraints

DON'T:

❌ Skip OpenAPI validation phase
❌ Assume reasonable defaults without documenting
❌ Report spec gaps as implementation bugs
❌ Test without understanding expected behavior

Example Report:

## OpenAPI Specification Gaps

### CRITICAL - No Validation Constraints
- **Endpoint**: POST /animal
- **Field**: systemPrompt
- **Issue**: No minLength, maxLength specified
- **Risk**: Unlimited input → DoS attack vector
- **Test Approach**: Testing with maxLength=5000 (reasonable default)
- **Recommendation**: Add `maxLength: 5000, minLength: 1`

Edge Case Testing

DO:

✅ Test ALL edge cases for ALL fields
✅ Include Unicode tests (Chinese, Arabic, emoji)
✅ Test security inputs (XSS, SQL injection, command injection)
✅ Test boundary conditions (min, max, below, above)
✅ Test type mismatches (string for number, etc.)
✅ Document expected behavior for each edge case

DON'T:

❌ Skip edge cases due to time pressure
❌ Assume validation works without testing
❌ Test only happy path scenarios
❌ Forget to test very large inputs
❌ Skip Unicode testing (international users exist!)

Edge Case Categories:

String Fields (25+ tests):

edge_cases = {
    # Length boundaries
    "empty": "",
    "single_char": "a",
    "at_min": "a" * min_length,
    "at_max": "a" * max_length,
    "below_min": "a" * (min_length - 1),  # Should fail
    "above_max": "a" * (max_length + 1),  # Should fail
    "very_large": "a" * 100000,           # Should fail

    # Unicode
    "chinese": "这是一个测试",
    "arabic": "هذا اختبار",
    "russian": "Это тест",
    "japanese": "これはテストです",
    "hebrew": "זה מבחן",
    "emojis": "🦁🐯🐻🦊",
    "mixed_unicode": "Hello 你好 مرحبا",
    "rtl": "مرحبا بك",  # Right-to-left text

    # Security (should all fail)
    "html_tags": "<script>alert('xss')</script>",
    "img_onerror": "<img src=x onerror=alert('xss')>",
    "sql_injection": "'; DROP TABLE animals; --",
    "command_injection": "; rm -rf /",
    "path_traversal": "../../etc/passwd",
    "null_bytes": "test\x00malicious",

    # Whitespace
    "leading_spaces": "  test",
    "trailing_spaces": "test  ",
    "multiple_spaces": "test    multiple",
    "only_spaces": "     ",
    "tabs": "test\t\ttabs",
    "newlines": "test\n\nnewlines",
    "mixed_whitespace": "  test \t\n  ",

    # Large content
    "lorem_ipsum": LOREM_500_CHARS,
    "five_paragraphs": LOREM_2000_CHARS,
    "very_large_block": "a" * 10000,
}

Numeric Fields (15+ tests):

edge_cases = {
    # Boundaries
    "zero": 0,
    "negative_one": -1,
    "negative_large": -999999,
    "at_minimum": minimum,        # If specified in OpenAPI
    "below_minimum": minimum - 1, # Should fail
    "at_maximum": maximum,        # If specified in OpenAPI
    "above_maximum": maximum + 1, # Should fail
    "very_large": 10**100,        # Should fail
    "very_small": -10**100,       # Should fail

    # Decimal precision (for floats)
    "high_precision": 0.123456789,
    "scientific_notation": 1e10,

    # Special values (should fail)
    "infinity": float('inf'),
    "negative_infinity": float('-inf'),
    "nan": float('nan'),

    # Type mismatches (should fail)
    "string": "not_a_number",
    "array": [1, 2, 3],
    "object": {"value": 5},
}

DynamoDB Persistence Verification

DO:

✅ Verify EVERY successful request persists to DynamoDB
✅ Compare ALL field values (not just primary key)
✅ Check nested objects preserved correctly
✅ Verify arrays contain correct items
✅ Validate timestamps populated
✅ Test data type preservation (number vs string)

DON'T:

❌ Assume persistence works without verification
❌ Only check if item exists (verify ALL fields)
❌ Skip verification for "simple" endpoints
❌ Forget to check nested/complex data structures

Verification Pattern:

# 1. Make REST API call
curl -X POST http://localhost:8080/animal \
  -H "Content-Type: application/json" \
  -d '{
    "animalId": "test_12345",
    "systemPrompt": "Test prompt",
    "temperature": 0.7,
    "details": {
      "age": 5,
      "habitat": "Forest"
    },
    "tags": ["mammal", "carnivore"]
  }' \
  -o response.json

# 2. Query DynamoDB
aws dynamodb get-item \
  --table-name cmz-animals \
  --key '{"animalId": {"S": "test_12345"}}' \
  --profile cmz \
  --output json > dynamo_item.json

# 3. Compare request with DynamoDB item
# Verify ALL fields match:
EXPECTED_PROMPT="Test prompt"
ACTUAL_PROMPT=$(jq -r '.Item.systemPrompt.S' dynamo_item.json)

if [ "$EXPECTED_PROMPT" != "$ACTUAL_PROMPT" ]; then
  echo "❌ PERSISTENCE MISMATCH: systemPrompt"
  echo "Expected: $EXPECTED_PROMPT"
  echo "Actual: $ACTUAL_PROMPT"
fi

# Verify nested objects
EXPECTED_AGE=5
ACTUAL_AGE=$(jq -r '.Item.details.M.age.N' dynamo_item.json)

if [ "$EXPECTED_AGE" != "$ACTUAL_AGE" ]; then
  echo "❌ PERSISTENCE MISMATCH: details.age"
fi

# Verify arrays
EXPECTED_TAG_COUNT=2
ACTUAL_TAG_COUNT=$(jq '.Item.tags.L | length' dynamo_item.json)

if [ "$EXPECTED_TAG_COUNT" != "$ACTUAL_TAG_COUNT" ]; then
  echo "❌ PERSISTENCE MISMATCH: tags array length"
fi

Test Cleanup

DO:

✅ Delete ALL test data after EVERY test
✅ Verify deletion succeeded
✅ Use unique identifiers (UUIDs) for test data
✅ Query for remaining test items at end
✅ Generate cleanup report

DON'T:

❌ Leave test data in production tables
❌ Assume deletion succeeded without verification
❌ Use static test IDs (causes conflicts)
❌ Skip cleanup on test failures

Cleanup Pattern:

# Generate unique test ID
TEST_ID="test_$(uuidgen)"

# Use in test
curl -X POST http://localhost:8080/animal \
  -d '{"animalId": "'${TEST_ID}'", ...}'

# After test (success or failure)
aws dynamodb delete-item \
  --table-name cmz-animals \
  --key '{"animalId": {"S": "'${TEST_ID}'"}}' \
  --profile cmz

# Verify deletion
ITEM=$(aws dynamodb get-item \
  --table-name cmz-animals \
  --key '{"animalId": {"S": "'${TEST_ID}'"}}' \
  --profile cmz \
  --output json)

if [ -n "$(echo $ITEM | jq '.Item')" ]; then
  echo "⚠️ CLEANUP FAILED: Item still exists"
else
  echo "✅ Cleanup successful"
fi

Final Verification (End of Testing):

# Query for ALL test items
aws dynamodb scan \
  --table-name cmz-animals \
  --filter-expression "begins_with(animalId, :prefix)" \
  --expression-attribute-values '{":prefix": {"S": "test_"}}' \
  --profile cmz \
  --output json

# Should return 0 items
ITEM_COUNT=$(echo $RESULT | jq '.Items | length')

if [ "$ITEM_COUNT" -eq 0 ]; then
  echo "✅ ALL test data cleaned up"
else
  echo "⚠️ WARNING: $ITEM_COUNT test items remain in DynamoDB"
  echo "Items: $(echo $RESULT | jq '.Items[].animalId.S')"
fi

"Not Implemented" Error Handling

CRITICAL: DO NOT immediately report as backend bug!

DO:

✅ Delegate to root-cause-analyst FIRST
✅ Check if handler exists in impl/ modules
✅ Verify controller routing is correct
✅ Check OpenAPI generation timestamps
✅ Look for "do some magic!" placeholders
✅ Classify error with evidence

DON'T:

❌ Report as backend bug without investigation
❌ Skip root cause analysis due to time pressure
❌ Assume all 501 errors are unimplemented features

Why This Matters:

OpenAPI regeneration FREQUENTLY disconnects handlers from controllers!

Symptoms:
- HTTP 501 Not Implemented
- "do some magic!" in controller
- Handler exists in impl/ but isn't called

Root Cause:
- `make generate-api` regenerates controllers
- Generated controller doesn't import handler
- Handler exists and works, but isn't connected

Solution:
- Run `make post-generate` after generation
- Fixes controller routing automatically
- Handler reconnected, endpoint works again

Investigation Pattern:

# ALWAYS delegate to root-cause-analyst
Task(
    subagent_type="root-cause-analyst",
    description="Investigate not implemented error",
    prompt="""Investigate 501/not implemented error on POST /animal.

    CRITICAL: Read ENDPOINT-WORK-ADVICE.md to understand OpenAPI patterns.

    Test Details:
    - Endpoint: POST /animal
    - Method: POST
    - Request: {"animalId": "test_123", "systemPrompt": "test"}
    - Response: {"error": "Not implemented"}
    - HTTP Status: 501

    Investigation Steps:
    1. Check if handler exists:
       grep -r "def handle_" backend/api/src/main/python/openapi_server/impl/animals.py

    2. Check controller routing:
       grep -A5 "def animal_post" backend/api/src/main/python/openapi_server/controllers/animal_controller.py

    3. Check for OpenAPI artifacts:
       grep "do some magic" backend/api/src/main/python/openapi_server/controllers/*.py

    4. Check generation timestamp:
       ls -la backend/api/src/main/python/openapi_server/controllers/

    Classify Error:
    - TRUE BUG: Handler missing or broken
    - OPENAPI ARTIFACT: Handler exists but controller disconnected
    - TEST ARTIFACT: Test setup issue (wrong URL, auth, etc.)

    Provide Evidence:
    - Handler location: impl/animals.py:45
    - Handler signature: def handle_animal_post(body)
    - Controller imports: from impl import animals vs. pass
    - "do some magic!" found: Yes/No
    - Generation timestamp: 2025-01-14 10:30 (after last impl/ change)
    - Classification: OPENAPI_ARTIFACT

    If OPENAPI_ARTIFACT:
    Recommendation: Run `make post-generate` to fix controller routing
    """
)

# WAIT for root-cause-analyst response
# THEN classify error based on evidence

Error Classification:

## Not Implemented Error Investigation

### Endpoint: POST /animal

**Error**: HTTP 501 Not Implemented

**Root Cause Analysis**: DELEGATED to root-cause-analyst

**Evidence Collected**:
- ✅ Handler EXISTS: `impl/animals.py:45`
- ✅ Handler signature: `def handle_animal_post(body)`
- ❌ Controller routing: Contains "do some magic!" placeholder
- ❌ Controller imports: `pass` instead of `from impl import animals`
- ⚠️ Generation timestamp: 2025-01-14 10:30 (AFTER handler implemented)

**Classification**: OPENAPI ARTIFACT (NOT a backend bug)

**Root Cause**: OpenAPI regeneration disconnected handler from controller

**Fix Required**: Run `make post-generate` to reconnect handler

**Test Status**: BLOCKED (not a test failure, infrastructure issue)

**Recommendation**: DO NOT report as backend bug

Troubleshooting

Issue: Tests Pass but Data Not in DynamoDB

Symptoms:

HTTP 200/201 responses
No errors in logs
DynamoDB query returns empty

Possible Causes:

Wrong Table Name

# Check environment variable
echo $FAMILY_DYNAMO_TABLE_NAME

# Verify table exists
aws dynamodb describe-table \
  --table-name $FAMILY_DYNAMO_TABLE_NAME \
  --profile cmz

Wrong Primary Key

# Check key schema
aws dynamodb describe-table \
  --table-name cmz-animals \
  --profile cmz \
  --query 'Table.KeySchema'

# Verify using correct key in query

Async Write (Eventual Consistency)

# Add delay before verification
sleep 2

# Query again
aws dynamodb get-item ...

Wrong AWS Profile

# Verify profile
aws sts get-caller-identity --profile cmz

# Should show CMZ account: 195275676211

Issue: Edge Cases Accepted When Should Reject

Symptoms:

Very large inputs accepted (should reject)
Invalid Unicode accepted (should reject)
Security inputs accepted (should reject)

Possible Causes:

OpenAPI Validation Not Enforced

Backend doesn't validate against OpenAPI spec
No validator middleware configured
Handler doesn't check input constraints

Solution:

## Bug Report: Input Validation Not Enforced

**Endpoint**: POST /animal
**Field**: systemPrompt
**Issue**: Accepts 100,000 character input (OpenAPI says maxLength: 5000)

**Reproduction**:
curl -X POST http://localhost:8080/animal \
  -d '{"systemPrompt": "'$(python -c "print('a' * 100000)")'"}'
# Returns HTTP 201 (should return HTTP 400)

**Root Cause**: Backend doesn't validate maxLength constraint

**Recommendation**:
1. Add connexion validator middleware
2. OR add validation in handler:
   if len(body['systemPrompt']) > 5000:
       return {"error": "systemPrompt too long"}, 400

OpenAPI Spec Missing Constraints

Field has no validation rules defined
Testing with reasonable defaults

Solution:

## OpenAPI Specification Gap

**Endpoint**: POST /animal
**Field**: systemPrompt
**Issue**: No maxLength constraint defined

**Test Approach**: Testing with maxLength=5000 (reasonable default)

**Recommendation**: Add to OpenAPI spec:
systemPrompt:
  type: string
  minLength: 1
  maxLength: 5000

Issue: DynamoDB Cleanup Fails

Symptoms:

Test items remain in DynamoDB after testing
"Item still exists" warnings

Possible Causes:

Delete Using Wrong Key

# Check table key schema
aws dynamodb describe-table \
  --table-name cmz-animals \
  --profile cmz \
  --query 'Table.KeySchema'

# Use correct key in delete
# If composite key (PK + SK):
aws dynamodb delete-item \
  --table-name cmz-animals \
  --key '{"animalId": {"S": "test_123"}, "sortKey": {"S": "value"}}' \
  --profile cmz

Conditional Delete Failing

# Remove condition expressions if present
# Simple delete without conditions:
aws dynamodb delete-item \
  --table-name cmz-animals \
  --key '{"animalId": {"S": "test_123"}}' \
  --profile cmz

Permissions Issue

# Verify delete permissions
aws iam get-user --profile cmz

# Check dynamodb:DeleteItem permission

Solution: Batch delete remaining items

# Find all test items
ITEMS=$(aws dynamodb scan \
  --table-name cmz-animals \
  --filter-expression "begins_with(animalId, :prefix)" \
  --expression-attribute-values '{":prefix": {"S": "test_"}}' \
  --profile cmz \
  --output json)

# Delete each item
echo $ITEMS | jq -r '.Items[].animalId.S' | while read ITEM_ID; do
  aws dynamodb delete-item \
    --table-name cmz-animals \
    --key "{\"animalId\": {\"S\": \"$ITEM_ID\"}}" \
    --profile cmz
  echo "Deleted: $ITEM_ID"
done

Issue: Too Many Tests, Takes Too Long

Symptoms:

Testing takes hours
1000+ edge case tests per endpoint

Solutions:

Prioritize Edge Cases

# Test critical edge cases first
critical_cases = [
    "empty",           # Length: empty string
    "above_max",       # Length: exceed maximum
    "sql_injection",   # Security: SQL injection
    "html_tags",       # Security: XSS
    "chinese",         # Unicode: non-English
    "very_large",      # DoS: huge input
]

# Test all edge cases only if critical tests pass

Parallel Testing

# Test multiple endpoints in parallel
/backend-testing --endpoint "POST /animal" &
/backend-testing --endpoint "POST /family" &
/backend-testing --endpoint "POST /conversation" &
wait

# Combine reports

Focus on High-Risk Fields

# Prioritize fields that:
# - Accept user input directly
# - Are used in security contexts (auth, permissions)
# - Are displayed to other users (XSS risk)
# - Are used in queries (SQL injection risk)
# - Have complex validation rules

# Skip comprehensive testing for:
# - Auto-generated fields (IDs, timestamps)
# - Internal-only fields
# - Enum fields with 2-3 values

Integration Patterns

Pattern 1: Complete Feature Testing

Use Case: Testing new feature end-to-end

# Step 1: Backend testing
Task(
    subagent_type="general-purpose",
    description="Backend comprehensive testing",
    prompt="""You are the Backend Testing Agent.

    Test animal-configuration feature comprehensively.

    See .claude/commands/backend-testing.md for methodology.

    Focus:
    - OpenAPI specification validation
    - All edge cases for all fields
    - DynamoDB persistence verification
    - Test cleanup

    Report findings in claudedocs/testing/backend/animal-configuration/
    """
)

# Step 2: Frontend testing (uses backend test results)
Task(
    subagent_type="general-purpose",
    description="Frontend comprehensive testing",
    prompt="""You are the Frontend Testing Agent.

    Test animal-configuration UI comprehensively.

    Prerequisites:
    - Backend testing complete (see report)
    - Backend endpoints verified working

    See .claude/commands/frontend-comprehensive-testing.md
    """
)

# Step 3: Documentation update
Task(
    subagent_type="general-purpose",
    description="Update feature documentation",
    prompt="""You are the Feature Documentation Agent.

    Update animal-configuration documentation with:
    - Validated edge cases from backend testing
    - Confirmed OpenAPI constraints
    - DynamoDB schema verified

    Input: claudedocs/testing/backend/animal-configuration/report.md

    See .claude/commands/document-features.md
    """
)

# Step 4: Teams notification
Task(
    subagent_type="general-purpose",
    description="Send test results to Teams",
    prompt="""You are the Teams Reporting Agent.

    Send animal-configuration test results.

    Read TEAMS-WEBHOOK-ADVICE.md, then:
    python3 scripts/send_teams_report.py test-results \
      --data claudedocs/testing/backend/animal-configuration/summary.json
    """
)

Pattern 2: OpenAPI Spec Validation Only

Use Case: Quick validation after OpenAPI changes

Task(
    subagent_type="general-purpose",
    description="Validate OpenAPI specification",
    prompt="""You are the Backend Testing Agent.

    Validate OpenAPI spec completeness (Phase 1 only).

    Steps:
    1. Read backend/api/openapi_spec.yaml
    2. For each endpoint, check all fields have:
       - minLength, maxLength (strings)
       - minimum, maximum (numbers)
       - required fields marked
       - examples provided
    3. Generate gap report
    4. Report critical gaps immediately

    DO NOT run tests. Only analyze specification.

    Output: claudedocs/testing/openapi-gaps-YYYY-MM-DD.md
    """
)

Pattern 3: Regression Testing

Use Case: Verify bug fix doesn't introduce regressions

Task(
    subagent_type="general-purpose",
    description="Regression testing after bug fix",
    prompt="""You are the Backend Testing Agent.

    Run regression tests for animal systemPrompt validation fix.

    Bug Fixed:
    - systemPrompt was accepting unlimited length
    - Fix: Added maxLength validation in handler

    Tests Required:
    1. Verify fix works:
       - Test systemPrompt with 5001 chars → should reject
       - Test systemPrompt with 5000 chars → should accept

    2. Verify no regressions:
       - Re-run ALL systemPrompt edge cases
       - Re-run other animal endpoint tests
       - Verify DynamoDB persistence still works

    Report any new failures immediately.

    See .claude/commands/backend-testing.md Phase 3
    """
)

Pattern 4: Coordinated with Test Orchestrator

Use Case: Complete validation suite

# Test orchestrator delegates to backend testing
Task(
    subagent_type="general-purpose",
    description="Orchestrate complete validation",
    prompt="""You are the Test Orchestrator.

    Coordinate complete validation for animal-configuration.

    Phase 2 (Backend Testing) - Delegate:
    - Backend comprehensive testing
    - OpenAPI validation
    - Edge case testing
    - DynamoDB verification

    Delegate to backend testing agent:

    Task(
        subagent_type="general-purpose",
        description="Backend testing phase",
        prompt="You are Backend Testing Agent. Test animal-configuration..."
    )

    See .claude/commands/orchestrate-tests.md Phase 2
    """
)

Success Metrics

Coverage Metrics:

✅ 100% of endpoints tested
✅ 100% of fields tested
✅ ≥25 edge cases per text field
✅ ≥10 edge cases per numeric field
✅ 100% of enum values tested
✅ 100% of DynamoDB persistence verified

Quality Metrics:

✅ ≥95% test pass rate (excluding known issues)
✅ Zero false positives (tests passing when should fail)
✅ 100% of "not implemented" errors investigated
✅ All OpenAPI gaps documented
✅ 100% test cleanup (no artifacts in DynamoDB)

Reporting Metrics:

✅ Comprehensive test report generated
✅ Reproduction steps for 100% of failures
✅ Root cause identified for all errors
✅ Recommendations prioritized by severity
✅ Teams notification sent

Integration Metrics:

✅ Backend architect received findings
✅ Feature documentation updated
✅ Frontend testing unblocked (backend working)
✅ Test orchestrator received status

Navigation Menu

Backend Testing Agent - Best Practices and Advice

Overview

When to Use Backend Testing Agent

Primary Use Cases

Integration Points

Best Practices

OpenAPI Specification Validation

Edge Case Testing

DynamoDB Persistence Verification

Test Cleanup

"Not Implemented" Error Handling

Troubleshooting

Issue: Tests Pass but Data Not in DynamoDB

Issue: Edge Cases Accepted When Should Reject

Issue: DynamoDB Cleanup Fails

Issue: Too Many Tests, Takes Too Long

Integration Patterns

Pattern 1: Complete Feature Testing

Pattern 2: OpenAPI Spec Validation Only

Pattern 3: Regression Testing

Pattern 4: Coordinated with Test Orchestrator

Success Metrics

Related Documentation

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File metadata and controls

Backend Testing Agent - Best Practices and Advice

Overview

When to Use Backend Testing Agent

Primary Use Cases

Integration Points

Best Practices

OpenAPI Specification Validation

Edge Case Testing

DynamoDB Persistence Verification

Test Cleanup

"Not Implemented" Error Handling

Troubleshooting

Issue: Tests Pass but Data Not in DynamoDB

Issue: Edge Cases Accepted When Should Reject

Issue: DynamoDB Cleanup Fails

Issue: Too Many Tests, Takes Too Long

Integration Patterns

Pattern 1: Complete Feature Testing

Pattern 2: OpenAPI Spec Validation Only

Pattern 3: Regression Testing

Pattern 4: Coordinated with Test Orchestrator

Success Metrics

Related Documentation