Explicit tests launching the viewer on every file type it compares

[SimonCropp]

Adds explicit tests that launch the viewer built from this working tree on a pair of every file type it compares other than text, so a person can check what each head actually draws. No product code changes.

What it adds

• FileTypeLaunchTests: 21 explicit cases, one per extension.

  • Images: .png, .bmp, .gif, .ico, .jpg, .jpeg, .webp.
  • A PDF.
  • .docx, .xlsx and .pptx.
  • An SVG.
  • Maps: .geojson, .topojson, .kml, .gpx, .wkt, .kmz, .wkb, .fgb and .geoparquet.

• What each case does:

  1. Asserts that DiffEngine would route that extension to the viewer.
  2. Writes a received and a verified file that differ visibly.
  3. Prints a checklist of what to look for.
  4. Launches through DiffRunner.LaunchAsync, the path a test run takes, and waits for the window to close.

• SampleImages builds the images.

  • BMP, ICO and GIF are written by hand, as SamplePng is.
  • JPEG and WebP are encoded with SkiaSharp.

• Other samples:

  • Office files are the committed samples with one string changed.
  • Maps are made by GeoConvert from one GeoJSON, with the point moved on one side.

• FileTypeSampleTests is an ordinary test (18 cases) that checks every generated sample on every run:

  • each image is the format and size it claims;
  • each Office edit shows up in the text;
  • every map format draws differently once moved.

  The launch tests are explicit, so without this a broken sample would only show up as an empty window.

Notes

• The class runs on port 3499 with the tray switched off, as GroupedQueue does. Otherwise a running DiffEngineTray takes each pair into its own queue and shows it in its installed viewer.
• The class raises MaxInstancesToLaunch, which is 5 by default and would refuse every launch after the fifth.
• The test project now references GeoConvert, SkiaSharp and SkiaSharp's Linux natives.

Run the class like this. Each window opens after the last one is closed:

dotnet test --project src/DiffEngineViewer.Tests -- --treenode-filter "/*/*/FileTypeLaunchTests/*"

Tests

• All 21 launch cases pass on Windows. They were run with each window captured and then closed.
• The viewer test project passes: 495 passed, 13 skipped.