add db mock

packages/hydrooj/test/db.ts

@@ -0,0 +1,18 @@
+import 'hydrooj/src/utils';
+
+jest.mock('hydrooj/src/service/db');
+
+export async function connect() {
+    await new Promise((resolve) => {
+        const db = require('hydrooj/src/service/db');
+        db.bus.once('connect', resolve);
+    });
+    const script = require('../src/script/upgrade0_1');
+    await script.run();
+}
+
+export async function dispose() {
+    const db = require('hydrooj/src/service/db');
+    await db.getClient().close();
+    await db.getDb().close();
+}