feat(testing): Add pytest fixtures for FlyteContext, cache, and tmp dirs

[mvanhorn]

Summary

Adds three pytest fixtures and a context manager to flytekit.testing, eliminating common test setup boilerplate. Fixtures auto-register via a pytest11 entry point so they're available without explicit imports.

Why this matters

Flytekit's testing module currently ships two utilities (task_mock and patch). Users writing tests for Flyte workflows repeat the same boilerplate across test files:

• FlyteContextManager.current_context() to get a context - appears 30+ times in flytekit's own test suite
• LocalTaskCache.initialize() / LocalTaskCache.clear() before cached task tests - the manual workaround discovered in flyteorg/flyte#5657
• tempfile.TemporaryDirectory() setup for file-based operations

Other workflow orchestrator SDKs ship dedicated testing utilities (Dagster's execute_in_process(), Prefect's prefect_test_harness, Airflow's pytest-airflow).

Changes

New files:

• flytekit/testing/fixtures.py - Three fixtures and one context manager:
  • flyte_context - returns the current FlyteContext
  • flyte_cache - initializes and clears LocalTaskCache before/after each test
  • flyte_tmp_dir - provides a managed Path temporary directory
  • workflow_dry_run() - context manager for clean local workflow execution
• flytekit/testing/conftest.py - pytest11 plugin entry point for auto-discovery
• tests/flytekit/unit/testing/test_fixtures.py - 12 tests covering all fixtures

Modified files:

• flytekit/testing/__init__.py - exports new fixtures
• pyproject.toml - registers [project.entry-points.pytest11] so fixtures are auto-available

Usage

# No import needed - fixtures auto-register via pytest11

def test_type_transform(flyte_context):
    lt = TypeEngine.to_literal_type(int)
    lv = TypeEngine.to_literal(flyte_context, 42, int, lt)
    assert lv.scalar.primitive.integer == 42

def test_cached_task(flyte_cache):
    # Cache cleared before and after - no flaky results from stale on-disk cache
    result = my_cached_task(a=1, b=2)
    assert result == 3

def test_file_ops(flyte_tmp_dir):
    path = flyte_tmp_dir / "output.txt"
    path.write_text("hello")
    assert path.read_text() == "hello"

Testing

All 12 tests pass locally on Python 3.12:

tests/flytekit/unit/testing/test_fixtures.py - 12 passed in 0.05s

Tests verify fixture behavior, cache isolation between tests, type transformations with context, and workflow dry-run execution.

This contribution was developed with AI assistance (Claude Code).