Add Large Mailbox Performance Tests for IMAP Client

[faizan-2022]

This PR introduces a set of integration tests to verify and optimize performance of the IMAP client when handling mailboxes containing 10,000+ messages. These tests ensure search speed, batch fetching, memory usage, pagination, and repeated operations meet acceptable performance standards.

1️⃣ Changes:

Added tests/unit/large-mailbox.test.ts to test:

Search performance with complex criteria (ALL, FROM, SINCE)

Efficient batch fetching of headers and full message bodies

UID-based pagination

Repeated fetches to check for memory leaks

Added error handling on IMAP client socket to prevent unhandled network errors (ECONNRESET)

Optional garbage collection (global.gc) used during large message fetches for memory management

Test execution gated with IMAP_PERF_TESTS=true to prevent running in CI

2️⃣ Criteria Verified:

✅ Search completes in <5s for 10k messages

✅ Memory usage stays bounded during large fetches

✅ UID-based pagination works correctly

✅ No memory leaks during repeated operations

3️⃣ How to Run Locally:

Run the following command in the terminal

IMAP_PERF_TESTS=true npm test tests/unit/large-mailbox.test.ts

4️⃣ Notes:

Requires a real IMAP server with a mailbox containing 10,000+ messages

Not intended for CI/CD environments

---

Important

Add performance tests for large mailboxes, Gmail label parsing, and MIME header handling in the IMAP client.

• Performance Tests:
  • Added large-mailbox.test.ts to test IMAP client performance with mailboxes of 10,000+ messages.
  • Tests search speed, batch fetching, memory usage, pagination, and repeated operations.
  • Includes error handling for network errors and optional garbage collection.
  • Tests are gated with IMAP_PERF_TESTS=true to prevent CI execution.
• Gmail Labels:
  • Added gmail-labels.test.ts to test parsing of Gmail system and custom labels.
  • Handles labels with spaces, nested labels, and special characters.
• MIME Header Parsing:
  • Added header-parser.test.ts to test handling of special characters in MIME headers.
  • Tests Unicode, RFC 2047 encoded words, and edge cases like long subjects and malformed headers.

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[ellipsis-dev]

Important

Looks good to me! 👍

Reviewed everything up to 3a09c14 in 56 seconds. Click for details.

• Reviewed 387 lines of code in 4 files
• Skipped 2 files when reviewing.
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1. package.json:117

• Draft comment:
  Missing trailing newline at end-of-file for consistency.
• Reason this comment was not posted:
  Confidence changes required: 50% <= threshold 50% None

2. tests/unit/gmail-labels.test.ts:101

• Draft comment:
  Gmail labels tests are solid; consider adding additional edge cases for deeper nested labels or alternative delimiters.
• Reason this comment was not posted:
  Confidence changes required: 33% <= threshold 50% None

3. tests/unit/header-parser.test.ts:81

• Draft comment:
  Header parser tests are comprehensive. Consider adding more variants of malformed encoded words to ensure robust fallback handling.
• Reason this comment was not posted:
  Confidence changes required: 33% <= threshold 50% None

4. tests/unit/large-mailbox.test.ts:82

• Draft comment:
  The 5-second threshold for search performance may be too strict on slower environments; consider parameterizing or documenting this dependency.
• Reason this comment was not posted:
  Confidence changes required: 33% <= threshold 50% None

5. tests/unit/large-mailbox.test.ts:150

• Draft comment:
  Repeated fetch tests use only 5 iterations; this may not capture subtle memory leaks. Consider implementing additional memory profiling.
• Reason this comment was not posted:
  Confidence changes required: 33% <= threshold 50% None

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