[TEST] MC/DC Integration Test Suite (Redis Module)

[VladRodionov]

MC/DC Integration Test Suite (Redis Module)

Summary

Introduce and maintain a Python-based integration test suite for the MC/DC Redis module that runs against a real Redis server with the module loaded. The tests validate command behavior, compression logic, and the command filter layer end‑to‑end.

The suite is executed via:

make itest

This target will:

• Build the MC/DC module (mcdc.so)
• Create / reuse a Python virtualenv (.venv)
• Install Python test dependencies from test/integration/requirements.txt
• Start a temporary Redis instance with MC/DC loaded
• Run pytest on test/integration/

---

Scope

1. Redis test harness

• test/integration/conftest.py:
  • Spawns a temporary Redis instance on a random free port using redis-server.
  • Loads the MC/DC module using --loadmodule with a test config:
    • MCDC_MODULE_PATH points to the built mcdc.so (defaults to ./build/mcdc.so).
    • Uses cfg=./test/integration/mcdc.conf so tests have a stable MC/DC configuration.
  • Waits for Redis to become ready (via PING).
  • Provides a redis_server session fixture that owns process lifecycle.
  • Provides an r fixture that:
    • Creates a Redis client bound to the test server
    • Calls FLUSHALL before each test to isolate state.

2. String command tests (test_strings.py)

Covers both direct MC/DC commands and filter-based rewrites.

Direct MC/DC string commands

• mcdc.set, mcdc.get round‑trip, for:

  • Small, non‑compressible values (e.g., "hello").
  • Large, highly compressible values (e.g., "X" * 512).

• Uses:

  • STRLEN key → logical size.
  • mcdc.cstrlen key → compressed / stored size.

• Assertions:

  • For small values (≤ 32 bytes): cstrlen >= strlen (no compression benefit expected).
  • For large compressible values: cstrlen < strlen.

• Similar coverage for:

  • mcdc.setex
  • mcdc.setnx
  • mcdc.psetex
  • mcdc.getex

Filter rewrites for strings

Verifies that plain Redis commands are transparently rewritten by the command filter when the key is in an MC/DC namespace (e.g., mcdc: prefix):

• SET key val → behaves like mcdc.set.
• GET key → behaves like mcdc.get.
• STRLEN key → routed to mcdc.strlen.

Tests check:

• Value equality on readback.
• Logical vs compressed size via STRLEN vs mcdc.cstrlen.

Async string commands

• mcdc.msetasync
• mcdc.mgetasync

Tests:

• Use multiple keys and values (mix of small + highly compressible values).
• Assert that:
  • mcdc.msetasync returns an OK‑style status (non‑error).
  • Subsequent mcdc.mgetasync returns a list with values equal to what was written.
  • Compression behavior still holds for large values (using mcdc.cstrlen).

---

3. Hash command tests (test_hashes.py)

Covers all hash commands implemented by MC/DC and their filter rewrites.

Direct MC/DC hash commands

• mcdc.hset / mcdc.hget round‑trip for:
  • Small values.
  • Large, compressible values.
• Compression verification:
  • Uses mcdc.hcstrlen key field to check stored size vs logical length.

Other covered commands:

• mcdc.hmget / mcdc.hset with multiple fields
• mcdc.hsetnx / mcdc.hgetdel
• mcdc.hvals
• mcdc.hgetall
• mcdc.hstrlen
• mcdc.hrandfield

Assertions include:

• Field presence and value equality.
• Correct length reporting via HSTRLEN / mcdc.hcstrlen.
• For compressible values: compressed size < logical size.

Filter rewrites for hashes

Verifies that plain Redis hash commands are rewritten when the key is in an MC/DC namespace:

• HSET → mcdc.hset / mcdc.hsetasync (depending on config)
• HMGET → mcdc.hmget / mcdc.hmgetasync
• HVALS → mcdc.hvals
• HGETALL → mcdc.hgetall
• HSTRLEN → mcdc.hstrlen
• HGET → mcdc.hget
• HRANDFIELD → mcdc.hrandfield

Tests ensure:

• Hash semantics remain identical to plain Redis behavior.
• Values are transparently compressed/decompressed.
• The filter does not interfere with non‑MC/DC keys.

Async hash commands

• mcdc.hsetasync
• mcdc.hmgetasync

Tests:

• Write multiple fields using mcdc.hsetasync.
• Read them via mcdc.hmgetasync and plain HMGET.
• Assert value equality and proper compression for large fields using mcdc.hcstrlen.

---

4. Redis version–specific behavior

Where needed (e.g., commands introduced in Redis 8+ like HSETEX), tests:

• Detect Redis server version via INFO SERVER.
• Skip tests if a feature is not available (e.g., running against Redis 7.2.5).

This keeps the suite compatible with current dev environments while still documenting behavior for newer versions.

---

Makefile Integration

The itest target:

• Depends on the Redis module being built: $(TARGET).
• Ensures a Python virtualenv exists (.venv).
• Installs dependencies from test/integration/requirements.txt.
• Runs pytest inside the venv, pointing MCDC_MODULE_PATH to the built module.

Example wiring:

PYTHON      ?= python3
VENV_DIR    ?= .venv
ITEST_DIR   ?= test/integration
REQ_FILE    ?= $(ITEST_DIR)/requirements.txt

PYTHON_BIN  := $(VENV_DIR)/bin/python
PIP_BIN     := $(VENV_DIR)/bin/pip
PYTEST_BIN  := $(VENV_DIR)/bin/pytest

.PHONY: venv
venv:
	@if [ ! -d "$(VENV_DIR)" ]; then \
	  echo "Creating Python virtualenv in $(VENV_DIR)..."; \
	  $(PYTHON) -m venv $(VENV_DIR); \
	fi; \
	echo "Upgrading pip..."; \
	"$(PIP_BIN)" install --upgrade pip >/dev/null; \
	if [ -f "$(REQ_FILE)" ]; then \
	  echo "Installing Python dependencies from $(REQ_FILE)..."; \
	  "$(PIP_BIN)" install -r "$(REQ_FILE)"; \
	else \
	  echo "WARNING: $(REQ_FILE) not found; skipping dependency install."; \
	fi

.PHONY: itest
itest: $(TARGET) venv
	@if [ ! -x "$(PYTEST_BIN)" ]; then \
	  echo "ERROR: pytest not installed in $(VENV_DIR)."; \
	  exit 1; \
	fi; \
	if [ ! -d "$(ITEST_DIR)" ]; then \
	  echo "ERROR: integration test directory '$(ITEST_DIR)' not found."; \
	  exit 1; \
	fi; \
	echo "Running integration tests using $(PYTEST_BIN) on $(ITEST_DIR)"; \
	MCDC_MODULE_PATH="$(TARGET)" "$(PYTEST_BIN)" -q "$(ITEST_DIR)"

---

Dependencies

test/integration/requirements.txt:

pytest>=8.0
pytest-timeout>=2.3
pytest-asyncio>=0.23
redis>=7.0

---

Acceptance Criteria

• make itest builds the module, sets up the venv, starts Redis, and runs all tests.
• All string and hash MC/DC commands have integration coverage (direct + filtered).
• Both compressible and non‑compressible values are tested via mcdc.cstrlen / mcdc.hcstrlen.
• Async commands (mcdc.mgetasync, mcdc.msetasync, mcdc.hmgetasync, mcdc.hsetasync) are fully validated (values and compression), not just “no error”.
• Non‑MC/DC keys behave like vanilla Redis (no filter interference).
• Tests pass on Redis 7.2.x with MC/DC loaded, with version‑specific tests skipped when features are unavailable.

[VladRodionov]

First cut is done. I will keep it open once I validate that all acceptance criteria are met.