Proposal: Dedicated unit test suite for default transports and response encoding

[janmejai2002]

Overview & Motivation

While httpx maintains dedicated unit test suites for ASGI (test_asgi.py) and WSGI (test_wsgi.py), the default transport implementations (HTTPTransport, AsyncHTTPTransport, ResponseStream, and AsyncResponseStream) in httpx/_transports/default.py are primarily exercised indirectly via higher-level client tests against live or mock test servers.

Additionally, httpx/_content.py defines dedicated response encoding helpers (encode_text, encode_html) and chunking boundaries (IteratorByteStream.CHUNK_SIZE = 65_536) that have few direct unit tests in tests/test_content.py.

To harden the transport lifecycle and content boundary handling, I've prepared a comprehensive, zero-mock unit test suite covering:

1. Stream Lifecycle Cleanup:
   • ResponseStream.close() and AsyncResponseStream.aclose() propagating cleanup to the underlying httpcore stream.
   • Safe fallback when wrapping streams that do not implement .close() / .aclose() (e.g. raw iterators/generators).
2. Transport Exception Mapping:
   • Parameterized tests ensuring httpcore.ReadTimeout, httpcore.ReadError, and httpcore.RemoteProtocolError raised during stream iteration are mapped to their public httpx counterparts (httpx.ReadTimeout, httpx.ReadError, httpx.RemoteProtocolError).
3. Transport Configuration & Environment Trust:
   • Verification of default connection pool settings (_http1 is True, _http2 is False, verify_mode == CERT_REQUIRED).
   • trust_env semantics: custom CA paths in SSL_CERT_FILE are validated when trust_env=True and cleanly ignored when trust_env=False.
   • Proxy protocol routing across direct, HTTP proxy, SOCKS proxy, and scheme validation.
4. Direct Content Encoding & Streaming:
   • Direct response encoding for text and html parameters populating appropriate Content-Length and Content-Type headers.
   • Zero-length string boundaries for text/html responses.
   • Chunked streaming for synchronous and asynchronous file-like objects spanning beyond the 65,536-byte chunk buffer.

Verification

All 89 unit tests across tests/test_transports.py and tests/test_content.py pass cleanly locally:

• tests/test_content.py: 55 passed
• tests/test_transports.py: 34 passed
• 89 passed in 7.79s
• 100% formatted and linted with ruff
• 0 synthetic mocks; tests run against genuine stdlib SSL contexts, standard streams, and httpcore exceptions.

The branch and commit are available on my fork here:
janmejai2002@0f95447

Would the maintainers be open to a pull request adding these test suites to tests/?