From 80ee2272bac19d1b2bc41c92a0a48bcbe67691c4 Mon Sep 17 00:00:00 2001
From: Henry Tsai <henrytsai@outlook.com>
Date: Fri, 5 Jul 2024 11:27:15 -0700
Subject: [PATCH] Better approach to testing process handlers

---
 src/process-handlers.ts              |  8 +++----
 tests/process-handler.spec.ts        | 32 +++++++++++++++++++++-------
 tests/scenarios/registration.spec.ts |  4 ----
 3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/src/process-handlers.ts b/src/process-handlers.ts
index e9f1b66..b9de6e6 100644
--- a/src/process-handlers.ts
+++ b/src/process-handlers.ts
@@ -59,8 +59,8 @@ export const unsetProcessHandlers = (handlers: ProcessHandlers): void => {
     sigtermHandler 
   } = handlers;
 
-  process.off('unhandledRejection', unhandledRejectionHandler);
-  process.off('uncaughtException', uncaughtExceptionHandler);
-  process.off('SIGINT', sigintHandler);
-  process.off('SIGTERM', sigtermHandler);
+  process.removeListener('unhandledRejection', unhandledRejectionHandler);
+  process.removeListener('uncaughtException', uncaughtExceptionHandler);
+  process.removeListener('SIGINT', sigintHandler);
+  process.removeListener('SIGTERM', sigtermHandler);
 };
\ No newline at end of file
diff --git a/tests/process-handler.spec.ts b/tests/process-handler.spec.ts
index 9ee7106..708c8fb 100644
--- a/tests/process-handler.spec.ts
+++ b/tests/process-handler.spec.ts
@@ -2,28 +2,25 @@ import { expect } from 'chai';
 import sinon from 'sinon';
 
 import { config } from '../src/config.js';
+import type { Dwn } from '@tbd54566975/dwn-sdk-js';
 import { DwnServer } from '../src/dwn-server.js';
 import { getTestDwn } from './test-dwn.js';
 import { Poller } from './poller.js';
 
 describe('Process Handlers', function () {
+  let dwn: Dwn;
   let dwnServer: DwnServer;
   let processExitStub: sinon.SinonStub;
 
   beforeEach(async function () {
-    const testDwn = await getTestDwn();
-    dwnServer = new DwnServer({ dwn: testDwn, config: config });
+    const dwn = await getTestDwn();
+    dwnServer = new DwnServer({ dwn, config: config });
     await dwnServer.start();
     processExitStub = sinon.stub(process, 'exit');
   });
 
   afterEach(async () => {
     await dwnServer.stop();
-    console.log('server stop in Process Handlers tests');
-
-    process.removeAllListeners('SIGINT');
-    process.removeAllListeners('SIGTERM');
-    process.removeAllListeners('uncaughtException');
     processExitStub.restore();
   });
 
@@ -45,16 +42,35 @@ describe('Process Handlers', function () {
     });
   });
 
-  it('should log an error for an uncaught exception', function () {
+  it('should log an error for an uncaught exception', async () => {
+
+    // IMPORTANT: this test is a bit tricky to write because
+    // existing process `uncaughtException` listener/handler will result will trigger an error when we force an `uncaughtException` event
+    // causing the test to fail. So we need to remove the existing listener and add them back after the test.
+    // To be in full control of the test, we also create the DWN server (which adds it's own `uncaughtException` listener)
+    // AFTER removing the existing listener.
+    await dwnServer.stop();
+
+    // storing then removing existing listeners and adding back at the very end of the test
+    const existingUncaughtExceptionListeners = [...process.listeners('uncaughtException')];
+    process.removeAllListeners('uncaughtException');
+
+    dwnServer = new DwnServer({ dwn, config: config });
+    await dwnServer.start();
+    
     const consoleErrorStub = sinon.stub(console, 'error'); // Stub console.error
     const errorMessage = 'Test uncaught exception';
     const error = new Error(errorMessage);
     process.emit('uncaughtException', error);
 
     // Ensure console.error was called with the expected error message
+    console.log('console.error call count', consoleErrorStub.callCount);
     expect(consoleErrorStub.calledOnce).to.be.true;
 
     // Restore the original console.error
     consoleErrorStub.restore();
+
+    // add back original listeners
+    existingUncaughtExceptionListeners.forEach(listener => process.on('uncaughtException', listener));
   });
 });
diff --git a/tests/scenarios/registration.spec.ts b/tests/scenarios/registration.spec.ts
index 7e2bc83..a826bc0 100644
--- a/tests/scenarios/registration.spec.ts
+++ b/tests/scenarios/registration.spec.ts
@@ -35,10 +35,6 @@ if (!globalThis.crypto) {
   globalThis.crypto = webcrypto;
 }
 
-console.log = (): void => {};
-console.error = (): void => {};
-console.info = (): void => {};
-
 describe('Registration scenarios', function () {
   const dwnMessageEndpoint = 'http://localhost:3000';
   const termsOfUseEndpoint = 'http://localhost:3000/registration/terms-of-service';