Merge pull request #1122 from JL03-Yue/JL03-Yue/error-issue

fix logging issue and add a logging unit test

vscode-dotnet-runtime-library/src/EventStream/LoggingObserver.ts

@@ -7,7 +7,7 @@ import { IEvent } from './IEvent';
 import { ILoggingObserver } from './ILoggingObserver';
 
 export class LoggingObserver implements ILoggingObserver {
-    private readonly log: string[] = [];
+    private log: string[] = [];
 
     constructor(private readonly logFilePath: string) {}
 
@@ -31,6 +31,6 @@ export class LoggingObserver implements ILoggingObserver {
     }
 
     private writeLine(line: string) {
-        this.log.concat(line);
+        this.log.push(line);
     }
 }

vscode-dotnet-runtime-library/src/test/unit/LoggingObserver.test.ts

@@ -0,0 +1,37 @@
+/* --------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation. All rights reserved.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ * ------------------------------------------------------------------------------------------ */
+import * as chai from 'chai';
+import * as fs from 'fs';
+import * as path from 'path';
+import { LoggingObserver } from '../../EventStream/LoggingObserver';
+import { MockEventStream } from '../mocks/MockObjects';
+import { DotnetUninstallAllStarted } from '../../EventStream/EventStreamEvents';
+const assert = chai.assert;
+
+suite('LoggingObserver Unit Tests', () => {
+    const eventStream = new MockEventStream();
+    const tempPath = path.join(__dirname,  `${ new Date().getTime()}` );
+
+    test('Log file is writing output', async () => {
+        // Create an empty folder
+        if (!fs.existsSync(tempPath)) {
+            fs.mkdirSync(tempPath);
+        }
+        // Create a logging observer
+        const loggingObserver = new LoggingObserver(path.join(tempPath, 'logTest.txt'));
+
+        // Create a fake event and call the post/dispose function
+        const fakeEvent = new DotnetUninstallAllStarted();
+        loggingObserver.post(fakeEvent);
+        loggingObserver.dispose();
+
+        // Check if the log file content is same as expected content
+        fs.readdirSync(tempPath).forEach(file => {
+            const logContent = fs.readFileSync(path.join(tempPath, file)).toString();
+            assert.include(logContent, fakeEvent.eventName, 'The log file does not contain the expected content that should be written to it?');
+        });
+
+    });
+});