Add unit tests for FileSystem.createReadStream/createWriteStream

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: iclanton

libraries/node-core-library/src/test/FileSystem.test.ts

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
 // See LICENSE in the project root for license information.
 
+import * as nodeJsOs from 'node:os';
 import fs from 'node:fs';
 
 import { FileSystem } from '../FileSystem';
@@ -51,4 +52,141 @@ describe(FileSystem.name, () => {
       }
     });
   });
+
+  describe(FileSystem.createReadStream.name, () => {
+    let tempDir: string;
+
+    beforeEach(() => {
+      tempDir = fs.mkdtempSync(`${nodeJsOs.tmpdir()}/filesystem-test-`);
+    });
+
+    afterEach(() => {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    });
+
+    test('returns a readable stream for an existing file', (done) => {
+      const filePath: string = `${tempDir}/test.txt`;
+      fs.writeFileSync(filePath, 'hello world');
+
+      const stream: fs.ReadStream = FileSystem.createReadStream(filePath);
+      const chunks: Buffer[] = [];
+
+      stream.on('data', (chunk: string | Buffer) => {
+        chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk);
+      });
+
+      stream.on('end', () => {
+        const result: string = Buffer.concat(chunks).toString();
+        expect(result).toBe('hello world');
+        done();
+      });
+
+      stream.on('error', done);
+    });
+
+    test('stream emits an error for a nonexistent file', (done) => {
+      const filePath: string = `${tempDir}/nonexistent.txt`;
+      const stream: fs.ReadStream = FileSystem.createReadStream(filePath);
+
+      stream.on('error', (error: NodeJS.ErrnoException) => {
+        expect(error.code).toBe('ENOENT');
+        done();
+      });
+    });
+  });
+
+  describe(FileSystem.createWriteStream.name, () => {
+    let tempDir: string;
+
+    beforeEach(() => {
+      tempDir = fs.mkdtempSync(`${nodeJsOs.tmpdir()}/filesystem-test-`);
+    });
+
+    afterEach(() => {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    });
+
+    test('creates a writable stream that writes data to a file', (done) => {
+      const filePath: string = `${tempDir}/output.txt`;
+      const stream: fs.WriteStream = FileSystem.createWriteStream(filePath);
+
+      stream.write('hello ');
+      stream.write('world');
+      stream.end(() => {
+        const result: string = fs.readFileSync(filePath, 'utf-8');
+        expect(result).toBe('hello world');
+        done();
+      });
+
+      stream.on('error', done);
+    });
+
+    test('emits an error when the parent folder does not exist and ensureFolderExists is not set', (done) => {
+      const filePath: string = `${tempDir}/nonexistent-folder/output.txt`;
+      const stream: fs.WriteStream = FileSystem.createWriteStream(filePath);
+
+      stream.on('error', (error: NodeJS.ErrnoException) => {
+        expect(error.code).toBe('ENOENT');
+        done();
+      });
+    });
+
+    test('creates the parent folder when ensureFolderExists is true', (done) => {
+      const filePath: string = `${tempDir}/new-folder/output.txt`;
+      const stream: fs.WriteStream = FileSystem.createWriteStream(filePath, {
+        ensureFolderExists: true
+      });
+
+      stream.write('test data');
+      stream.end(() => {
+        const result: string = fs.readFileSync(filePath, 'utf-8');
+        expect(result).toBe('test data');
+        done();
+      });
+
+      stream.on('error', done);
+    });
+  });
+
+  describe('createWriteStreamAsync', () => {
+    let tempDir: string;
+
+    beforeEach(() => {
+      tempDir = fs.mkdtempSync(`${nodeJsOs.tmpdir()}/filesystem-test-`);
+    });
+
+    afterEach(() => {
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    });
+
+    test('creates a writable stream that writes data to a file', async () => {
+      const filePath: string = `${tempDir}/output.txt`;
+      const stream: fs.WriteStream = await FileSystem.createWriteStreamAsync(filePath);
+
+      await new Promise<void>((resolve, reject) => {
+        stream.on('error', reject);
+        stream.write('async hello');
+        stream.end(() => resolve());
+      });
+
+      const result: string = fs.readFileSync(filePath, 'utf-8');
+      expect(result).toBe('async hello');
+    });
+
+    test('creates the parent folder when ensureFolderExists is true', async () => {
+      const filePath: string = `${tempDir}/new-folder/output.txt`;
+      const stream: fs.WriteStream = await FileSystem.createWriteStreamAsync(filePath, {
+        ensureFolderExists: true
+      });
+
+      await new Promise<void>((resolve, reject) => {
+        stream.on('error', reject);
+        stream.write('async test data');
+        stream.end(() => resolve());
+      });
+
+      const result: string = fs.readFileSync(filePath, 'utf-8');
+      expect(result).toBe('async test data');
+    });
+  });
 });