test(services): add tests for service layer functions

test/services/metadata/metadataWritingService.test.js

@@ -0,0 +1,75 @@
+import { expect } from 'chai';
+import sinon from 'sinon';
+import esmock from 'esmock';
+
+describe('writeMetadataService', function() {
+  let writeMetadataStub;
+  let writeMetadataService;
+
+  const validMetadata = {
+    title: 'Test Title',
+    artist: 'Test Artist',
+    lyrics: 'Test Lyrics',
+    filePath: 'path/to/test/file.mp3',
+  };
+
+  const invalidMetadata = {
+    title: 'Test Title',
+    artist: 'Test Artist',
+    lyrics: 'Test Lyrics',
+    filePath: '',  // Invalid file path
+  };
+
+  beforeEach(async function() {
+    writeMetadataStub = sinon.stub().resolves();
+
+    // Mocking writeMetadata and its dependencies
+    writeMetadataService = await esmock('../../../src/services/metadata/metadataWritingService.js', {
+      '../../../src/services/metadata/metadataWriters/writeMetadata.js': { default: writeMetadataStub }
+    });
+
+    writeMetadataService = writeMetadataService.default;
+  });
+
+  afterEach(() => {
+    sinon.restore();
+    esmock.purge();
+  });
+
+  it('should write metadata to all files in the array', async function() {
+    const metadataArray = [validMetadata, validMetadata];
+
+    await writeMetadataService(metadataArray);
+
+    // Ensure writeMetadata is called twice
+    expect(writeMetadataStub.calledTwice).to.be.true;
+    expect(writeMetadataStub.alwaysCalledWith(validMetadata, validMetadata.filePath)).to.be.true;
+  });
+
+  it('should skip metadata objects without a file path', async function() {
+    const metadataArray = [validMetadata, invalidMetadata, { title: 'No FilePath' }];
+
+    await writeMetadataService(metadataArray);
+
+    // Ensure writeMetadata is called only once for the valid metadata
+    expect(writeMetadataStub.calledOnceWithExactly(validMetadata, validMetadata.filePath)).to.be.true;
+  });
+
+  it('should handle errors during the writing of metadata', async function() {
+    const error = new Error('Failed to write metadata');
+    writeMetadataStub.rejects(error);
+
+    const metadataArray = [validMetadata];
+
+    try {
+      await writeMetadataService(metadataArray);
+    } catch (e) {
+      expect.fail('No error should be thrown from service');
+    }
+
+    // Ensure error is logged (this would normally go to your logging mechanism)
+    expect(writeMetadataStub.calledOnceWithExactly(validMetadata, validMetadata.filePath)).to.be.true;
+    // Check if console.error was called (mock console.error if needed)
+  });
+});
+