test: migrate suite to SnapDiff canonical names

[pftg]

v2 step 8 (ADR-004): the test suite now exercises the canonical SnapDiff:: names everywhere except tests whose purpose IS the legacy surface. Test-only change — no lib/ edits.

What changed

1. Old-name references migrated to SnapDiff:: equivalents (26 test files): ImageCompare → Comparison, Difference → ComparisonResult, SnapManager, ScreenshotAssertion, Vcs, StableScreenshoter, Screenshoter, BrowserHelpers, Reporters::HTML, Snap, DSL, plus the ScreenshoterStub superclass. Test-class nesting under the old modules was kept (references migrated, classes not renamed, per proportionate-churn).

2. Suite-wide deprecation silencing replaced with a loud guard. #218's global SnapDiff.silence_deprecations = true is gone. Instead test_helper installs a Warning.extend hook that raises on any [snap_diff deprecation] warning, so accidental old-name use inside the suite fails at the resolution site. Legacy-surface tests opt out per test:

• namespace_forwarding_test silences deprecations in its own setup/teardown (it resolves every mapped old name on purpose);
• legacy_namespace_deprecation_test / snap_diff_deprecation_test set SnapDiffDeprecationGuard.expected around the warnings they capture and assert on (a module flag, not a thread-local, so warnings emitted from threads a test spawns are covered — the deprecation thread-safety test needs exactly that).

3. Deliberate legacy keeps (each scoped + documented in place):

• test/unit/namespace_forwarding_test.rb, test/unit/legacy_namespace_deprecation_test.rb, test/unit/support_load_probe_test.rb — their purpose is the legacy surface.
• test/unit/snap_diff_test.rb — the alias-pinning test ("SnapDiff::Comparison aliases …ImageCompare") keeps the old name with local silencing; its sibling assertions migrated.
• test/unit/static_test.rb — one of three cases now pins the legacy CapybaraScreenshotDiff.serve forwarder; the other two use canonical SnapDiff.serve.
• test/fixtures/rspec_*.rb — keep require "capybara_screenshot_diff/rspec" (legacy entry point under test); incidental SnapManager refs migrated.
• test/system_test_case.rb — keeps include Capybara::Screenshot::Diff (the v1 mixin path) and include CapybaraScreenshotDiff::Minitest::Assertions, so the integration suite still exercises the legacy DSL entry end-to-end.
• Not migrated because they are the canonical current homes, not shims: Capybara::Screenshot/Diff mattr config accessors (storage of record per SnapDiff::Config delegation), Capybara::Screenshot::Diff::AVAILABLE_DRIVERS, CapybaraScreenshotDiff session surface (reset/verify/registry/…) and error classes (ExpectationNotMet etc.), top-level Region, Capybara::Screenshot::Diff::Reporters::Default.

Shim-coverage gaps checked: the legacy DSL mixin (include Capybara::Screenshot::Diff) stays covered via system_test_case; the legacy rspec/minitest entry points via the fixtures and entry-point probes; TestMethods does not exist in lib — no new tests needed. Finding (out of scope for this test-only PR): the session surface (reset/verify/registry) and error classes exist only on CapybaraScreenshotDiff, with no SnapDiff equivalent yet.

Evidence

• Baseline (6df54dc) and after: rake test:unit 488 runs / 0 failures / 0 errors / 0 skips; rake test 521 runs / 0 failures / 6 skips — unchanged run counts, zero deprecation output on stderr.
• Empirical sweep: ran the unit suite unsilenced before migrating — 24 distinct old constants warned; after migration: 0.
• Mutation check: reintroducing Capybara::Screenshot::Diff::Vcs in migrated dsl_test.rb → RuntimeError: old-namespace constant resolved inside the test suite … raised from the guard (then restored).
• standardrb test/ — 62 files, no offenses.

🤖 Generated with Claude Code

Summary by Sourcery

Make the test suite validate canonical SnapDiff APIs and fail loudly on unintended legacy namespace usage.

Enhancements:

• Migrate the test suite to exercise canonical SnapDiff:: names while retaining explicitly scoped coverage for legacy namespaces and entry points.
• Replace global deprecation silencing with a suite-wide guard that fails on unexpected legacy-name warnings and supports intentional deprecation tests.

Tests:

• Update test references, fixtures, helpers, and integration coverage to use canonical APIs while preserving deliberate legacy-surface assertions.

[sourcery-ai]

Reviewer's Guide

Migrates the test suite from legacy CapybaraScreenshotDiff/Capybara::Screenshot::Diff constant names to the canonical SnapDiff:: API, and replaces the prior global deprecation silencing with an explicit guard that raises on unexpected shim usage, while keeping a handful of targeted legacy-surface tests and entry points intact and documented.

File-Level Changes

Change	Details	Files
Migrate tests from legacy CapybaraScreenshotDiff / Capybara::Screenshot::Diff constants to canonical SnapDiff:: names.	Repoint usages of ImageCompare to SnapDiff::Comparison and Difference to SnapDiff::ComparisonResult in helpers and driver contract tests. Replace CapybaraScreenshotDiff::SnapManager and related calls (snapshot, path_for, cleanup!, screenshots, instance.root) with SnapDiff::SnapManager equivalents. Switch DSL mixin, screenshot assertion classes, browser helpers, reporters, Vcs, StableScreenshoter, Screenshoter, and ScreenshotMatcher references to their SnapDiff:: counterparts. Update non-Minitest and integration tests (including rspec fixtures and DSL stubs) to depend on SnapDiff::DSL and SnapDiff::.* services while preserving legacy require/include entry points where intentionally under test. Keep test class/module nesting under CapybaraScreenshotDiff/Capybara::Screenshot::Diff where appropriate, only migrating constant references to avoid noisy renames.	test/fixtures/rspec_after_hook_order_masking_spec.rb test/fixtures/rspec_pending_masking_spec.rb test/fixtures/rspec_spec.rb test/integration/browser_screenshot_test.rb test/integration/report_screenshot_test.rb test/integration/test_methods_system_test.rb test/support/capybara_screenshot_diff/dsl_stub.rb test/support/driver_contract_tests.rb test/support/non_minitest_assertions.rb test/support/screenshoter_stub.rb test/system_test_case.rb test/test_helper.rb test/unit/attempts_reporter_test.rb test/unit/diff_test.rb test/unit/dsl_test.rb test/unit/minitest_assertions_test.rb test/unit/reporter_interplay_test.rb test/unit/screenshot_assertion_test.rb test/unit/screenshot_matcher_test.rb test/unit/screenshot_test.rb test/unit/screenshoter_test.rb test/unit/snap_diff_test.rb test/unit/stable_screenshoter_test.rb test/unit/static_test.rb
Introduce a suite-wide deprecation guard that raises on unexpected legacy shim usage and let specific tests opt out.	Remove global SnapDiff.silence_deprecations = true from test_helper and instead define a SnapDiffDeprecationGuard module that hooks Warning.warn. In the guard, raise when a message contains the snap_diff deprecation tag and no expectation flag is set, otherwise delegate to the original warn. Extend Warning with SnapDiffDeprecationGuard in test_helper so it is active across the suite, and document the non-thread-local expected flag semantics. Mark legacy_namespace_deprecation_test and snap_diff_deprecation_test as expected emitters by toggling SnapDiffDeprecationGuard.expected around their warning assertions. Add per-test silencing of SnapDiff.silence_deprecations in namespace_forwarding_test and the alias-pinning test in snap_diff_test so their deliberate legacy constant resolutions do not trip the guard.	test/test_helper.rb test/unit/legacy_namespace_deprecation_test.rb test/unit/namespace_forwarding_test.rb test/unit/snap_diff_deprecation_test.rb test/unit/snap_diff_test.rb
Preserve and document intentional legacy entry points and surfaces under test.	Keep require "capybara_screenshot_diff/rspec" in rspec fixtures while migrating incidental SnapManager references to SnapDiff::SnapManager. Retain include Capybara::Screenshot::Diff and CapybaraScreenshotDiff::Minitest::Assertions in system_test_case to ensure the integration suite still exercises the v1 DSL mixin path end-to-end. Explicitly leave Capybara::Screenshot/Diff mattr config accessors, AVAILABLE_DRIVERS, CapybaraScreenshotDiff session surface and error classes, Region, and the default reporter on their existing namespaces since they are current homes rather than shims. Annotate the StaticTest case that uses CapybaraScreenshotDiff.serve as deliberately pinning the legacy forwarder while other StaticTest cases call SnapDiff.serve. Document in tests where legacy use is necessary (namespace_forwarding_test, legacy_namespace_deprecation_test, support_load_probe_test, rspec fixtures, system_test_case) that they are exercising the legacy surface by design.	test/fixtures/rspec_spec.rb test/system_test_case.rb test/unit/static_test.rb test/unit/namespace_forwarding_test.rb test/unit/legacy_namespace_deprecation_test.rb test/unit/support_load_probe_test.rb

Possibly linked issues

• #ADR-004: The test-only migration advances ADR-004’s SnapDiff canonical namespace transition and validates legacy shims remain intentional.

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Run ID: 084b318f-0b00-492e-8944-b6d8e1994417

📥 Commits

Reviewing files that changed from the base of the PR and between 6df54dc and ac02b6e.

📒 Files selected for processing (27)

• test/fixtures/rspec_after_hook_order_masking_spec.rb
• test/fixtures/rspec_pending_masking_spec.rb
• test/fixtures/rspec_spec.rb
• test/integration/browser_screenshot_test.rb
• test/integration/report_screenshot_test.rb
• test/integration/test_methods_system_test.rb
• test/support/capybara_screenshot_diff/dsl_stub.rb
• test/support/driver_contract_tests.rb
• test/support/non_minitest_assertions.rb
• test/support/screenshoter_stub.rb
• test/system_test_case.rb
• test/test_helper.rb
• test/unit/attempts_reporter_test.rb
• test/unit/diff_test.rb
• test/unit/dsl_test.rb
• test/unit/legacy_namespace_deprecation_test.rb
• test/unit/minitest_assertions_test.rb
• test/unit/namespace_forwarding_test.rb
• test/unit/reporter_interplay_test.rb
• test/unit/screenshot_assertion_test.rb
• test/unit/screenshot_matcher_test.rb
• test/unit/screenshot_test.rb
• test/unit/screenshoter_test.rb
• test/unit/snap_diff_deprecation_test.rb
• test/unit/snap_diff_test.rb
• test/unit/stable_screenshoter_test.rb
• test/unit/static_test.rb

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