test(aws-lambda): expand handler unit tests for processors and createResult

[rokasta12]

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

Adds 48 new unit tests to src/adapter/aws-lambda/handler.test.ts, expanding coverage from 12 to 60 test cases. The handler.ts coverage improves to 77% statements, 90% branches, 85% functions.

What's covered

ALBProcessor (previously untested at the unit level)

• createRequest with single-value and multi-value headers
• getQueryString with queryStringParameters and multiValueQueryStringParameters
• Priority of multiValueQueryStringParameters over queryStringParameters
• Cookie extraction from both header formats
• Base64-encoded body decoding

createResult

• multiValueHeaders vs headers format based on event type
• content-encoding binary detection (gzip/br triggering base64)
• set-cookie handling for all 4 event types:
  • V2 → result.cookies array
  • V1 → result.multiValueHeaders['set-cookie']
  • ALB (single headers) → serialized with ,
  • ALB (multi-value) → result.multiValueHeaders['set-cookie']
  • Lattice → serialized with , into result.headers
• Empty body (204) and custom status codes

getDomainName fallback chain

• requestContext.domainName (API Gateway)
• headers.host (ALB)
• multiValueHeaders.host (ALB with multi-value enabled)
• Lattice host from array headers

getProcessor

• All 4 processor types: ALBProcessor, EventV1Processor, EventV2Processor, LatticeV2Processor

Non-ASCII header sanitization

• V1 multiValueHeaders with non-ASCII values
• ALB single headers with non-ASCII values
• ALB multiValueHeaders joining with ; and sanitizing

Base64 body decoding

• V1 and V2 events with isBase64Encoded: true
• Pass-through for non-base64 bodies

LatticeV2Processor

• Query string from path (getQueryString returns '')
• Set-cookie serialization

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.48%. Comparing base (d2ed2e9) to head (c3b5bf6).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4744   +/-   ##
=======================================
  Coverage   91.48%   91.48%           
=======================================
  Files         177      177           
  Lines       11556    11556           
  Branches     3358     3359    +1     
=======================================
  Hits        10572    10572           
  Misses        983      983           
  Partials        1        1           

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