test: refactor deprecate-helpers.ts to warning-helpers.ts (#46808)

Add a generic expectWarningMessages and start checking warning names

spec/lib/warning-helpers.ts

@@ -0,0 +1,60 @@
+import { expect } from 'chai';
+
+type ExpectedWarningMessage = RegExp | string;
+
+async function expectWarnings (
+  func: () => any,
+  expected: { name: string, message: ExpectedWarningMessage }[]
+) {
+  const messages: { name: string, message: string }[] = [];
+
+  const originalWarn = console.warn;
+  console.warn = (message) => {
+    messages.push({ name: 'Warning', message });
+  };
+
+  const warningListener = (error: Error) => {
+    messages.push({ name: error.name, message: error.message });
+  };
+
+  process.on('warning', warningListener);
+
+  try {
+    return await func();
+  } finally {
+    // process.emitWarning seems to need us to wait a tick
+    await new Promise(process.nextTick);
+    console.warn = originalWarn;
+    process.off('warning' as any, warningListener);
+    expect(messages).to.have.lengthOf(expected.length);
+    for (const [idx, { name, message }] of messages.entries()) {
+      expect(name).to.equal(expected[idx].name);
+      if (expected[idx].message instanceof RegExp) {
+        expect(message).to.match(expected[idx].message);
+      } else {
+        expect(message).to.equal(expected[idx].message);
+      }
+    }
+  }
+}
+
+export async function expectWarningMessages (
+  func: () => any,
+  ...expected: ({ name: string, message: ExpectedWarningMessage } | ExpectedWarningMessage)[]
+) {
+  return expectWarnings(func, expected.map((message) => {
+    if (typeof message === 'string' || message instanceof RegExp) {
+      return { name: 'Warning', message };
+    } else {
+      return message;
+    }
+  }));
+}
+
+export async function expectDeprecationMessages (
+  func: () => any, ...expected: ExpectedWarningMessage[]
+) {
+  return expectWarnings(
+    func, expected.map((message) => ({ name: 'DeprecationWarning', message }))
+  );
+}