Fixes #3956. Refactor unit test projects: rename UnitTests→Legacy, add NonParallelizable, eliminate Legacy tests

[Copilot]

Implements all steps of the test project refactoring. The repo now has three well-defined test tiers, and the Legacy project has been fully emptied — reduced from ~1,004 tests to 0.

Proposed Changes/Todos

• Update Tests/README.md with static state documentation and decision table
• Rename Tests/UnitTests → Tests/UnitTests.Legacy
• Create Tests/UnitTests.NonParallelizable and move obvious non-parallelizable tests
• Fix Tests/IntegrationTests/IntegrationTests.csproj project reference broken by rename
• Update .github/workflows/README.md to reflect new project names
• Step 4 iteration 1: Delete 37 Legacy test files already covered in UnitTestsParallelizable
• Step 4 iteration 2: Delete 14 more Legacy test files (Application, Clipboard, WizardTests, etc.)
• Step 4 iteration 3: Delete 5 more Legacy test files (Config, TextViewHistory, TreeViewMatcher)
• Step 4 iteration 4: Delete UICatalog tests; move ConfigurationMangerTests + GlyphTests to NonParallelizable
• Step 4 iterations 5–6: Delete FrameViewTests, StatusBarTests
• Step 4 iteration 7: SpinnerViewTests — 2 new Para tests, Legacy deleted
• Step 4 iteration 8: TreeTableSourceTests — 4 new Para tests, Legacy deleted
• Step 4 iteration 9: SynchronizatonContextTests — 2 new NonParallelizable tests, Legacy deleted
• Step 4 iteration 10: TreeViewFileSystemNavigationTests — 3 new Para tests, Legacy deleted
• Step 4 iteration 11: TabViewTests — deleted from Legacy (TabView being rewritten)
• Step 4 iteration 12: AppendAutocompleteTests — 4 new Para tests, Legacy deleted
• Step 4 iteration 13: ProgressBarTests — 4 new Para tests, Legacy deleted
• Step 4 iteration 14: FileDialogTests — 13 new Para tests (AllowedType.IsAllowed), Legacy deleted
• Step 4 iteration 15: GraphViewTests — 8 new Para tests, Legacy deleted
• Step 4 iteration 16: TableViewTests — 15 new Para tests, Legacy deleted (0 Legacy tests remaining)
• Fix CI: remove Run UnitTests.Legacy step from .github/workflows/unit-tests.yml (empty project returned exit code 8)
• Fix SynchronizationContextTests: rewrite to use modern instance model (Application.Create()) instead of legacy Application.Init()/Application.Shutdown()
• Audit entire UnitTests.NonParallelizable project to ensure all tests use the modern instance model; confirm only ApplicationModelFencingTests uses ApplicationImpl.Instance (with proper ResetModelUsageTracking() guards)
• Merge origin/v2_develop (IAdornment/IAdornmentView breaking change): resolve 15 modify/delete conflicts by keeping Legacy deletions

Tests/README.md

• Documents all process-wide static state (Application, ApplicationImpl, ConfigurationManager, View.Diagnostics) with member-level tables
• Adds decision table: which project a test belongs in based on its static-state usage

Tests/UnitTests → Tests/UnitTests.Legacy

• Directory, .csproj, .sln, .DotSettings all renamed via git mv (history preserved)
• AssemblyName set to UnitTests.Legacy; InternalsVisibleTo entry updated in Terminal.Gui.csproj
• UnitTestsParallelizable.csproj and IntegrationTests.csproj path references updated
• README updated: "do not add tests here"
• CI job updated to Tests/UnitTests.Legacy

Tests/UnitTests.NonParallelizable additions

• ConfigurationMangerTests.cs moved from Legacy (uses global ConfigurationManager.Enable/Disable/Load/Apply static state)
• GlyphTests.cs moved from Legacy (uses ConfigurationManager static state)
• SynchronizationContextTests.cs added — tests that Application.Create() + app.Init() sets SynchronizationContext.Current and app.Dispose() clears it (modern instance model only; legacy Application.Init is not used)
• NonParallelizable now has 57 passing tests (up from 22)

NonParallelizable model correctness

All tests in UnitTests.NonParallelizable use the modern instance model (Application.Create() + app.Init() + app.Dispose()). The only exception is ApplicationModelFencingTests, which explicitly tests the legacy/modern fencing mechanism and correctly calls ApplicationImpl.ResetModelUsageTracking() at the start and end of every test. Application.ResetState(true) in ConfigurationMangerTests calls ApplicationImpl.ResetStateStatic() which resets model tracking without going through the fence-checked Instance getter — safe to use in NonParallelizable tests. Application.DefaultKeyBindings/GetDefaultKey() in KeyboardSetterTests are pure static data properties with no model fence involvement.

Step 4: Legacy test elimination (16 iterations, each a separate commit)

Files deleted where UnitTestsParallelizable already has equivalent or better coverage, or new minimal tests were written first:

• Iterations 1–6: 57 Legacy test files deleted (views, layout, drawing, navigation, configuration, application, UICatalog)
• Iteration 7 (SpinnerViewTests): New Para tests for throttle and frame-advance behavior
• Iteration 8 (TreeTableSourceTests): New Para tests for keyboard/mouse expand-collapse and checkbox toggle
• Iteration 9 (SynchronizatonContextTests): New NonParallelizable tests for SyncContext lifecycle
• Iteration 10 (TreeViewFileSystemNavigationTests): New Para tests for FileSystemCollectionNavigationMatcher
• Iteration 11 (TabViewTests): Deleted without replacement (TabView being rewritten)
• Iteration 12 (AppendAutocompleteTests): New Para tests — Esc/Tab/cycle key handling and suggestion lifecycle
• Iteration 13 (ProgressBarTests): New Para tests — style→segment char, text override, fraction and Pulse rendering
• Iteration 14 (FileDialogTests): New Para tests for AllowedType.IsAllowed — basic, double-barreled, and specific-file extension matching
• Iteration 15 (GraphViewTests): New Para tests — coordinate conversion, MultiBarSeries, AxisIncrementToRender, LegendAnnotation
• Iteration 16 (TableViewTests): New Para tests — selection, scroll validation, CheckBox source, EnumerableTableSource, column captions

CI Fixes

• Tests/IntegrationTests/IntegrationTests.csproj was referencing the old ..\UnitTests\UnitTests.csproj path after the rename. Updated to ..\UnitTests.Legacy\UnitTests.Legacy.csproj.
• Removed Run UnitTests.Legacy step from .github/workflows/unit-tests.yml — the project is now empty, so dotnet test returned exit code 8 ("Zero tests ran"), causing the Non-Parallel Unit Tests CI job to fail on all three OS platforms.
• Fixed SynchronizationContextTests — the tests were using Application.Init() (legacy static model), which throws InvalidOperationException after any test using Application.Create() (modern instance model) runs in the same process. Rewrote both tests to use Application.Create() + app.Init() + app.Dispose(). The SynchronizationContext behavior is set in ApplicationImpl.Init(), which is called identically by both models.

Merge: origin/v2_develop (IAdornment breaking change)

Merged the Fixes #4696. BREAKING CHANGE - Lazy Adornment Views via IAdornment + IAdornmentView split commit from v2_develop. There were 15 modify/delete conflicts — all files in Tests/UnitTests/ that v2_develop modified but this branch had already deleted as part of the Legacy cleanup (iterations 1–16). Resolved by keeping the deletions. Build succeeds with zero code warnings; all 57 NonParallelizable tests pass.

Test results

Project	Passed	Skipped
UnitTests.Legacy	0	0
UnitTests.NonParallelizable	57	2
UnitTestsParallelizable	15 001	18

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Refactor Unit Tests</issue_title>
<issue_description>There should be 3 projects:

• UnitTests.Parallelizable - the vast majority of tests. Any test that is guaranteed to not use legacy APIs or static, process-wide state.
• UnitTests.NonParallelizable. Tests that either explicitly test process-wide static state, or must set process-wide statics, or otherwise cannot be run concurrently with other tests.
• UnitTests.Legacy. Tests that have not yet been ported to the other two projects (or deleted because they are duplicates of existing tests.

Each of the following steps should be completed before moving on to next. This includes ensuring all test projects run and pass and ci/cd workflows run without errors.

• 1. Update the /Tests/README.md with a list of all static properties in project and their purpose. Include documentation on each part of the library that would impact whether a test can go in each of the unit test projects described above.
• 2. Rename UnitTests to UnitTests.Legacy
• 3. Create UnitTests.NonParralelizable and move obvious tests that match the definition from UnitTests.Legacy.

Then, iterate on the following until the legacy project has no remaining tests. Each iteration must result in a separate commit where all test projects pass and ci/cd is run without failure.

• For each test class in legacy, study the test and the code it preports to test. Study the relevant tests in the other two unit test projects and either rewrite if the case is not already covered (do not port. Assume the old tests are poorly written) or delete if the case already has coverage. New tests should be as minimal as possible- test one thing, do not depend on things if not needed, do not depend on other View subclasses from ./Views unless absolutely required (instead create
  Test specific View subclasses or use existing testviews).

Double check that existing patterns for test class names, namespaces, and folder structures are followed and maintained (agents often get this wrong).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Refactor Unit Tests #4844

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[tig]

@copilot you did not follow instructions. The gh workflows are failing.

[Copilot]

@copilot you did not follow instructions. The gh workflows are failing.

Fixed in b940474. The CI build was failing because Tests/IntegrationTests/IntegrationTests.csproj still referenced the old ../UnitTests/UnitTests.csproj path after the rename. Updated it to ../UnitTests.Legacy/UnitTests.Legacy.csproj. Also updated .github/workflows/README.md to reflect the new project names.

[tig]

@copilot now do step 4. You must verify the gh actions have no failures at the end of each iteration and fix any issues before moving on.

[Copilot]

@copilot now do step 4. You must verify the gh actions have no failures at the end of each iteration and fix any issues before moving on.

Done in commits b6d58d6 through 18ea1bb. Step 4 progress:

6 iterations completed (each a separate commit with all tests passing):

• Deleted 57 Legacy test files already covered by UnitTestsParallelizable (views, layout, drawing, navigation, configuration, etc.)
• Moved ConfigurationMangerTests and GlyphTests to NonParallelizable (they use static ConfigurationManager state)
• Deleted UICatalog tests (test the UICatalog app, not the library)

Results:

Project	Before	After
Legacy	~1,004	243 passing
NonParallelizable	22	55 passing
UnitTestsParallelizable	14,948	unchanged

10 Legacy files remain with unique functionality not yet covered in Para: TabViewTests (31), TableViewTests (77), GraphViewTests (44), FileDialogTests (16), ProgressBarTests (9), AppendAutocompleteTests (8), TreeViewFileSystemNavigationTests (4), TreeTableSourceTests (3), SpinnerViewTests (3), SynchronizatonContextTests (3). These require new minimal tests to be written in Para before the Legacy versions can be deleted.

[tig]

@copilot continue on step 4 working from the test classes with the least number of tests. Do one per iteration. Think hard and proceed with care. Do not make mistakes or take shortcuts.

[tig]

@copilot you can ignore tabview tests. That's all being rewritten

[Copilot]

@copilot the non-parallel tests are mixing legacy and modern app instanced methods incorrectly. This failure occurred in the ubuntu runner. You must review the entire test project to...

Fixed in a5e953d. SynchronizationContextTests was using Application.Init() (legacy static model), but ApplicationKeyboardThreadSafetyTests runs first and uses Application.Create() (modern model) — once the modern model is used in the process, the legacy model throws InvalidOperationException. Rewrote both tests in SynchronizationContextTests to use the modern instance model (Application.Create() + app.Init() + app.Dispose()). The SynchronizationContext behavior under test is set in ApplicationImpl.Init() which is invoked identically by both models. All 57 NonParallelizable tests pass locally.

[tig]

@copilot did you review the rest of the project for other invalid uses like this as I asked?

[Copilot]

@copilot did you review the rest of the project for other invalid uses like this as I asked?

Yes, the full project was reviewed. The entire Tests/UnitTests.NonParallelizable project is clean:

• No Application.Init()/Application.Shutdown() in any test code (only in README.md docs)
• ApplicationImpl.Instance only appears in ApplicationModelFencingTests.cs, which tests the fencing mechanism and correctly calls ApplicationImpl.ResetModelUsageTracking() at the start and end of every test
• Application.ResetState(true) in ConfigurationMangerTests.cs calls ApplicationImpl.ResetStateStatic() internally, which resets model tracking without going through the fence-checked Instance getter — safe
• Application.DefaultKeyBindings/GetDefaultKey() in KeyboardSetterTests.cs are pure static data properties with no model fence involvement
• All app lifecycle tests (SynchronizationContextTests, ApplicationKeyboardThreadSafetyTests) use Application.Create() + app.Init() + app.Dispose() (modern instance model)

[tig]

@copilot fix merge issues

[Copilot]

@copilot fix merge issues

Done in 36dad4e. Merged origin/v2_develop (IAdornment/IAdornmentView breaking change). There were 15 modify/delete conflicts — all files in Tests/UnitTests/ that v2_develop modified but our branch had already deleted as part of the Legacy cleanup. Resolved by keeping our deletions. Build succeeds with zero code warnings; all 57 NonParallelizable tests pass.