test: improve 'running queries' detection

(backport of #12885)

test/integration/support.js

 'use strict';
 
+// Store local references to `setTimeout` and `clearTimeout` asap, so that we can use them within `p-timeout`,
+// avoiding to be affected unintentionally by `sinon.useFakeTimers()` called by the tests themselves.
+const { setTimeout, clearTimeout } = global;
+
+const pTimeout = require('p-timeout');
 const Support = require('../support');
 
-const runningQueries = new Set();
+const CLEANUP_TIMEOUT = Number.parseInt(process.env.SEQ_TEST_CLEANUP_TIMEOUT, 10) || 10000;
+
+let runningQueries = new Set();
 
 before(function() {
   this.sequelize.addHook('beforeQuery', (options, query) => {
@@ -13,15 +20,53 @@ before(function() {
   });
 });
 
-beforeEach(function() {
-  return Support.clearDatabase(this.sequelize);
+beforeEach(async function() {
+  await Support.clearDatabase(this.sequelize);
 });
 
-afterEach(function() {
-  if (runningQueries.size === 0) {
-    return;
+afterEach(async function() {
+  // Note: recall that throwing an error from a `beforeEach` or `afterEach` hook in Mocha causes the entire test suite to abort.
+
+  let runningQueriesProblem;
+
+  if (runningQueries.size > 0) {
+    runningQueriesProblem = `Expected 0 queries running after this test, but there are still ${
+      runningQueries.size
+    } queries running in the database (or, at least, the \`afterQuery\` Sequelize hook did not fire for them):\n\n${
+      // prettier-ignore
+      [...runningQueries].map(query => `       ${query.uuid}: ${query.sql}`).join('\n')
+    }`;
+  }
+
+  runningQueries = new Set();
+
+  try {
+    await pTimeout(
+      Support.clearDatabase(this.sequelize),
+      CLEANUP_TIMEOUT,
+      `Could not clear database after this test in less than ${CLEANUP_TIMEOUT}ms. This test crashed the DB, and testing cannot continue. Aborting.`,
+      { customTimers: { setTimeout, clearTimeout } }
+    );
+  } catch (error) {
+    let message = error.message;
+    if (runningQueriesProblem) {
+      message += `\n\n     Also, ${runningQueriesProblem}`;
+    }
+    message += `\n\n     Full test name:\n       ${this.currentTest.fullTitle()}`;
+
+    // Throw, aborting the entire Mocha execution
+    throw new Error(message);
+  }
+
+  if (runningQueriesProblem) {
+    if (this.test.ctx.currentTest.state === 'passed') {
+      // `this.test.error` is an obscure Mocha API that allows failing a test from the `afterEach` hook
+      // This is better than throwing because throwing would cause the entire Mocha execution to abort
+      this.test.error(new Error(`This test passed, but ${runningQueriesProblem}`));
+    } else {
+      console.log(`     ${runningQueriesProblem}`);
+    }
   }
-  throw new Error(`Expected 0 running queries. ${runningQueries.size} queries still running in ${this.currentTest.fullTitle()}`);
 });
 
 module.exports = Support;