Write a little (mocked) test

Author: juliasilge

apps/vscode/src/lsp/client.ts

@@ -348,12 +348,11 @@ function isWithinYamlComment(doc: TextDocument, pos: Position) {
 /**
  * Creates a diagnostic handler middleware that filters out diagnostics from virtual documents
  *
- * @param enabled Whether filtering is enabled
  * @returns A handler function for the middleware
  */
-function createDiagnosticFilter() {
+export function createDiagnosticFilter() {
   return (uri: Uri, diagnostics: Diagnostic[], next: HandleDiagnosticsSignature) => {
-    // If filtering is disabled or this is not a virtual document, pass through all diagnostics
+    // If this is not a virtual document, pass through all diagnostics
     if (!isVirtualDoc(uri)) {
       next(uri, diagnostics);
       return;

apps/vscode/src/test/diagnosticFiltering.test.ts

@@ -0,0 +1,53 @@
+import * as vscode from "vscode";
+import * as assert from "assert";
+import { createDiagnosticFilter } from "../lsp/client";
+
+suite("Diagnostic Filtering", function () {
+
+  test("Diagnostic filter removes diagnostics for virtual documents", async function () {
+    // Create mocks
+    const virtualDocUri = vscode.Uri.file("/tmp/.vdoc.12345678-1234-1234-1234-123456789abc.py");
+    const regularDocUri = vscode.Uri.file("/tmp/regular-file.py");
+
+    // Create some test diagnostics
+    const testDiagnostics = [
+      new vscode.Diagnostic(
+        new vscode.Range(0, 0, 0, 10),
+        "Test diagnostic message",
+        vscode.DiagnosticSeverity.Error
+      )
+    ];
+
+    // Create a mock diagnostics handler function to verify behavior
+    let capturedUri: vscode.Uri | undefined;
+    let capturedDiagnostics: vscode.Diagnostic[] | undefined;
+
+    const mockHandler = (uri: vscode.Uri, diagnostics: vscode.Diagnostic[]) => {
+      capturedUri = uri;
+      capturedDiagnostics = diagnostics;
+    };
+
+    // Create the filter function
+    const diagnosticFilter = createDiagnosticFilter();
+
+    // Test with a virtual document
+    diagnosticFilter(virtualDocUri, testDiagnostics, mockHandler);
+
+    // Verify diagnostics were filtered (empty array)
+    assert.strictEqual(capturedUri, virtualDocUri, "URI should be passed through");
+    assert.strictEqual(capturedDiagnostics!.length, 0, "Diagnostics should be empty for virtual documents");
+
+    // Reset captured values
+    capturedUri = undefined;
+    capturedDiagnostics = undefined;
+
+    // Test with a regular document
+    diagnosticFilter(regularDocUri, testDiagnostics, mockHandler);
+
+    // Verify diagnostics were not filtered
+    assert.strictEqual(capturedUri, regularDocUri, "URI should be passed through");
+    assert.strictEqual(capturedDiagnostics!.length, testDiagnostics.length, "Diagnostics should not be filtered for regular documents");
+    assert.deepStrictEqual(capturedDiagnostics!, testDiagnostics, "Original diagnostics should be passed through unchanged");
+  });
+
+});