fix: Output required OAuth error fields

test/unit/util/errors/OAuthHttpError.test.ts

@@ -0,0 +1,24 @@
+import { OAuthHttpError } from '../../../../src/util/errors/OAuthHttpError';
+
+describe('An OAuthHttpError', (): void => {
+  it('contains relevant information.', async(): Promise<void> => {
+    const error = new OAuthHttpError({ error: 'error!' }, 'InvalidRequest', 400, 'message!');
+    expect(error.mandatoryFields.error).toBe('error!');
+    expect(error.name).toBe('InvalidRequest');
+    expect(error.statusCode).toBe(400);
+    expect(error.message).toBe('message!');
+  });
+
+  it('has optional fields.', async(): Promise<void> => {
+    const error = new OAuthHttpError({ error: 'error!' });
+    expect(error.mandatoryFields.error).toBe('error!');
+    expect(error.name).toBe('OAuthHttpError');
+    expect(error.statusCode).toBe(500);
+  });
+
+  it('can identify OAuth errors.', async(): Promise<void> => {
+    const error = new OAuthHttpError({ error: 'error!' });
+    expect(OAuthHttpError.isInstance('apple')).toBe(false);
+    expect(OAuthHttpError.isInstance(error)).toBe(true);
+  });
+});