test: add debugger integration coverage for pytest processpool child sessions

Agent-Logs-Url: https://github.com/microsoft/vscode-python-debugger/sessions/573cd841-8f08-4cd0-8021-229e2380164f

Co-authored-by: rchiodo <19672699+rchiodo@users.noreply.github.com>

Author: Copilot

src/test/pythonFiles/debugging/test_pytest_processpool.py

@@ -0,0 +1,28 @@
+import os
+import random
+import time
+from concurrent.futures import ProcessPoolExecutor, wait as futures_wait
+
+
+def worker_func() -> int:
+    time_to_sleep = random.randint(1, 2) / 10
+    time.sleep(time_to_sleep)
+    return int(time_to_sleep * 10)
+
+
+def library_function() -> None:
+    futures = []
+    with ProcessPoolExecutor(max_workers=4) as pool:
+        for _ in range(8):
+            futures.append(pool.submit(worker_func))
+        done, _ = futures_wait(futures)
+        for fut in done:
+            _ = fut.result()
+
+
+def test_library_process_pool() -> None:
+    library_function()
+    done_file = os.environ.get("DEBUG_DONE_FILE")
+    if done_file:
+        with open(done_file, "w", encoding="utf-8") as fp:
+            fp.write("done")

src/test/unittest/adapter/adapter.test.ts

@@ -21,8 +21,10 @@ function resolveWSFile(wsRoot: string, ...filePath: string[]): string {
 
 suite('Debugger Integration', () => {
     const file = resolveWSFile(WS_ROOT, 'pythonFiles', 'debugging', 'wait_for_file.py');
+    const processPoolTestFile = resolveWSFile(WS_ROOT, 'pythonFiles', 'debugging', 'test_pytest_processpool.py');
     const doneFile = resolveWSFile(WS_ROOT, 'should-not-exist');
     const outFile = resolveWSFile(WS_ROOT, 'output.txt');
+    const processPoolDoneFile = resolveWSFile(WS_ROOT, 'pytest-processpool-debug-done.txt');
     const resource = vscode.Uri.file(file);
     const defaultScriptArgs = [doneFile];
     let workspaceRoot: vscode.WorkspaceFolder;
@@ -107,4 +109,36 @@ suite('Debugger Integration', () => {
             });
         }
     });
+
+    suite('pytest multiprocess test debugging', () => {
+        test('processpool test reaches code after worker joins in debug-test session', async function () {
+            this.timeout(120_000);
+            fix.addFSCleanup(processPoolDoneFile);
+
+            const config = {
+                type: 'python',
+                name: 'debug pytest processpool',
+                request: 'launch',
+                module: 'pytest',
+                args: ['-s', processPoolTestFile, '-k', 'test_library_process_pool'],
+                console: 'integratedTerminal',
+                purpose: ['debug-test'],
+                subProcess: true,
+                cwd: WS_ROOT,
+                env: {
+                    DEBUG_DONE_FILE: processPoolDoneFile,
+                },
+            };
+
+            const session = fix.resolveDebuggerWithConfig(config, workspaceRoot);
+            await session.start();
+            const result = await session.waitUntilDone();
+
+            expect(result.exitCode).to.equal(0, 'bad exit code');
+            expect(await fs.pathExists(processPoolDoneFile)).to.equal(
+                true,
+                'pytest test did not reach code after process pool join',
+            );
+        });
+    });
 });

src/test/unittest/utils.ts

@@ -277,6 +277,16 @@ class DebuggerSession {
 }
 
 export class DebuggerFixture extends PythonFixture {
+    public resolveDebuggerWithConfig(
+        config: vscode.DebugConfiguration,
+        wsRoot?: vscode.WorkspaceFolder,
+    ): DebuggerSession {
+        const id = debuggers.track(config);
+        const session = new DebuggerSession(id, config, wsRoot);
+        debuggers.setDAPHandler(id, (src, msg) => session.handleDAPMessage(src, msg));
+        return session;
+    }
+
     public resolveDebugger(
         configName: string,
         file: string,