test(f7.1): host E2E — changed flowchart augments emitted source (#22)

Adds a renderHtmlFor test seam to TrackChangesPreviewController.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/trackChangesPreview.ts

@@ -214,6 +214,14 @@ export class TrackChangesPreviewController implements vscode.Disposable {
   getLastModel(uriString: string): BlockOp[] | undefined {
     return this.lastModel.get(uriString);
   }
+  /** F7.1 (#22) test seam: the track-changes HTML the panel would post for a doc. */
+  renderHtmlFor(uriString: string): string {
+    const doc = vscode.workspace.textDocuments.find((d) => d.uri.toString() === uriString);
+    if (!doc) return "";
+    const current = doc.getText();
+    const baseline = this.diffView.getBaseline(uriString);
+    return renderTrackChanges(baseline?.text ?? current, current);
+  }
   /** F9: current view mode for a panel (default track-changes). */
   getMode(uriString: string): "changes" | "authorship" {
     return this.mode.get(uriString) ?? "changes";

test/e2e/suite/trackChangesPreview.test.ts

@@ -105,4 +105,31 @@ suite("F7 track-changes preview (host E2E — markdown only, programmatic seam,
     await settle();
     assert.strictEqual(api.trackChangesPreviewController.isOpen(key), false, "no panel for non-markdown");
   });
+
+  test("a changed flowchart augments the emitted mermaid source (#22, INV-29)", async () => {
+    const doc = await openDoc();
+    const api = await getApi();
+    // Show the preview and pin the baseline so the fixture's `a --> b` flowchart
+    // is the "before"; then add an edge `a --> c` and confirm the intra-diagram diff.
+    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
+    await vscode.commands.executeCommand("cowriting.pinDiffBaseline");
+    await settle();
+
+    const anchor = doc.getText().indexOf("a --> b");
+    assert.ok(anchor >= 0, "fixture contains the flowchart edge");
+    const insertAt = doc.positionAt(anchor + "a --> b".length);
+    const edit = new vscode.WorkspaceEdit();
+    edit.insert(doc.uri, insertAt, "\n  a --> c");
+    assert.ok(await vscode.workspace.applyEdit(edit), "flowchart edit applied");
+    await settle();
+
+    const model = api.trackChangesPreviewController.getLastModel(docUri()) ?? [];
+    const mermaidOp = model.find((o) => o.kind === "changed" && o.block.type === "mermaid");
+    assert.ok(mermaidOp, "the flowchart block is a changed mermaid op");
+
+    const html = api.trackChangesPreviewController.renderHtmlFor(docUri());
+    assert.match(html, /classDef cwAdded/, "augmented with cwAdded classDef");
+    assert.match(html, /class\s+c\s+cwAdded/, "node c colored added");
+    assert.match(html, /cw-mermaid-legend/, "legend emitted");
+  });
 });