Fix async interrupt tests timing out on Windows (#211)

Add a short delay before calling interrupt() in the Database.interrupt()
and Statement.interrupt() tests to ensure the query is actively running
on the tokio runtime. Without the delay, the interrupt flag can be set
before sqlite3_step() starts, causing a race condition where the flag
gets consumed without effect on Windows.

Author: penberg

integration-tests/tests/async.test.js

@@ -344,6 +344,10 @@ test.serial("Database.interrupt()", async (t) => {
   const db = t.context.db;
   const stmt = await db.prepare("WITH RECURSIVE infinite_loop(n) AS (SELECT 1 UNION ALL SELECT n + 1 FROM infinite_loop) SELECT * FROM infinite_loop;");
   const fut = stmt.all();
+  // Wait for the query to start executing on the tokio runtime before
+  // interrupting, otherwise the interrupt flag may be set before the first
+  // sqlite3_step() and get consumed without effect on some platforms.
+  await new Promise(resolve => setTimeout(resolve, 100));
   db.interrupt();
   await t.throwsAsync(async () => {
     await fut;
@@ -359,6 +363,7 @@ test.serial("Statement.interrupt()", async (t) => {
   const db = t.context.db;
   const stmt = await db.prepare("WITH RECURSIVE infinite_loop(n) AS (SELECT 1 UNION ALL SELECT n + 1 FROM infinite_loop) SELECT * FROM infinite_loop;");
   const fut = stmt.all();
+  await new Promise(resolve => setTimeout(resolve, 100));
   stmt.interrupt();
   await t.throwsAsync(async () => {
     await fut;