chore: reorg tests to mirror module structure, scope CI to changed files

[mikemadeja]

Summary

Two related changes, as requested:

1. Test folder reorg. Every per-function test file moves from a flat tests/ directory into tests/<Category>/, mirroring PiHoleShell/Public/<Category>/ exactly - e.g. PiHoleShell/Public/Actions/Invoke-PiHoleFlushNetwork.ps1 now pairs with tests/Actions/Invoke-PiHoleFlushNetwork.Integration.Tests.ps1. Shared support files (IntegrationConfig.example.ps1, IntegrationConfig.local.ps1, Initialize-PiHoleTestData.ps1) stay at tests/ root since they don't belong to any single function. Git tracked all 33 moves as renames. Updated every moved file's $PSScriptRoot-relative lookups for those shared files accordingly - Pester discovers tests recursively by default, so no change was needed on the Pester/pipeline path side for this part.

2. CI scoped to changed files. This mirroring is what makes this straightforward: the Azure DevOps pipeline now scopes PR builds to only the test file(s) matching whatever PiHoleShell/Public/<Category>/<Function>.ps1 files actually changed, instead of always running the entire suite (which includes many real-server integration tests individually taking 10-40+ seconds).

Direct pushes to develop/main still always run the full suite unchanged. On a PR build, anything that isn't a clean 1:1 function-to-test-file match falls back to the full suite rather than risk silently skipping coverage:

• Changes to PiHoleShell/Private/*, PiHoleShell.psm1/.psd1, or the shared Request-PiHoleAuth helper (used by every function)
• Changes to the shared test helpers (Initialize-PiHoleTestData.ps1, IntegrationConfig.example.ps1)
• Any failure computing the diff itself (git fetch/diff error)
• No test-relevant files changed at all (e.g. a docs-only PR)

Changed test files run directly; non-code changes (README, workflows, tools/) are ignored/have no effect on scope.

Test plan

• Validated the scoping logic in isolation against 10 scenarios (single function change, multi-category change, function with no test file, shared/private file changes, docs-only change, direct test-file change) - all behaved as designed
• Ran the actual dry-run script against this PR's real git diff vs develop - correctly resolved to exactly the 33 moved test files (this PR itself only touches tests, so that's the right scope)
• Invoke-ScriptAnalyzer -Path .\PiHoleShell -Recurse - clean
• Full non-integration suite passes with the new nested discovery (113 tests found, same as before the move)
• Re-ran a representative slice of the moved integration tests (History, Config, Authentication - 20 tests) against the real Pi-hole server to confirm the $PSScriptRoot path fixes work end-to-end, not just in isolation

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