fix: return contenttype header value string with parameters

test/unit/http/output/metadata/ContentTypeMetadataWriter.test.ts

@@ -0,0 +1,43 @@
+import { createResponse } from 'node-mocks-http';
+import { ContentTypeMetadataWriter } from '../../../../../src/http/output/metadata/ContentTypeMetadataWriter';
+import { RepresentationMetadata } from '../../../../../src/http/representation/RepresentationMetadata';
+import type { HttpResponse } from '../../../../../src/server/HttpResponse';
+
+describe('A ContentTypeMetadataWriter', (): void => {
+  const writer = new ContentTypeMetadataWriter();
+  let response: HttpResponse;
+
+  beforeEach(async(): Promise<void> => {
+    response = createResponse() as HttpResponse;
+  });
+
+  it('adds no header if there is no relevant metadata.', async(): Promise<void> => {
+    const metadata = new RepresentationMetadata();
+    await expect(writer.handle({ response, metadata })).resolves.toBeUndefined();
+    expect(response.getHeaders()).toEqual({ });
+  });
+
+  it('adds a Content-Type header with parameters if present.', async(): Promise<void> => {
+    const metadata = new RepresentationMetadata('text/plain; charset=utf-8');
+    await expect(writer.handle({ response, metadata })).resolves.toBeUndefined();
+
+    expect(response.getHeaders()).toEqual({
+      'content-type': 'text/plain; charset=utf-8',
+    });
+
+    const metadata2 = new RepresentationMetadata('text/plain; charset="utf-8"');
+    await expect(writer.handle({ response, metadata: metadata2 })).resolves.toBeUndefined();
+    expect(response.getHeaders()).toEqual({
+      'content-type': 'text/plain; charset=utf-8',
+    });
+  });
+
+  it('adds a Content-Type header without parameters.', async(): Promise<void> => {
+    const metadata = new RepresentationMetadata('text/plain');
+    await expect(writer.handle({ response, metadata })).resolves.toBeUndefined();
+
+    expect(response.getHeaders()).toEqual({
+      'content-type': 'text/plain',
+    });
+  });
+});