add test, fix comment

packages/node/src/local/cohort/cohort-api.ts

@@ -24,11 +24,9 @@ export interface CohortApi {
   getCohort(options?: GetCohortOptions): Promise<Cohort>;
 }
 
-export class CohortMaxSizeExceededError extends Error {}
-
-export class CohortClientRequestError extends Error {}
-
-export class CohortDownloadError extends Error {}
+export class CohortClientRequestError extends Error {} // 4xx errors except 429
+export class CohortMaxSizeExceededError extends CohortClientRequestError {} // 413 error
+export class CohortDownloadError extends Error {} // All other errors
 
 export class SdkCohortApi implements CohortApi {
   private readonly cohortApiKey;
@@ -86,7 +84,7 @@ export class SdkCohortApi implements CohortApi {
       response.status < 500 &&
       response.status != 429
     ) {
-      // Any 400 other than 429.
+      // Any 4xx other than 429.
       throw new CohortClientRequestError(
         `Cohort client error response status ${response.status}, body ${response.body}`,
       );

packages/node/test/local/cohort/cohortFetcher.test.ts

@@ -1,4 +1,5 @@
 import {
+  CohortClientRequestError,
   CohortMaxSizeExceededError,
   SdkCohortApi,
 } from 'src/local/cohort/cohort-api';
@@ -38,7 +39,7 @@ const COHORTS = {
   },
 };
 
-beforeEach(() => {
+afterEach(() => {
   jest.clearAllMocks();
 });
 
@@ -155,6 +156,27 @@ test('cohort fetch maxSize exceeded, no retry', async () => {
   });
 });
 
+test('cohort fetch client error, no retry', async () => {
+  const cohortApiGetCohortSpy = jest.spyOn(SdkCohortApi.prototype, 'getCohort');
+  cohortApiGetCohortSpy.mockImplementation(async () => {
+    throw new CohortClientRequestError();
+  });
+
+  const cohortFetcher = new CohortFetcher('', '', null, 'someurl', 10, 100);
+  const cohortPromise = cohortFetcher.fetch('c1', 10);
+
+  await expect(cohortPromise).rejects.toThrowError();
+  expect(cohortApiGetCohortSpy).toHaveBeenCalledTimes(1);
+  expect(cohortApiGetCohortSpy).toHaveBeenCalledWith({
+    cohortId: 'c1',
+    lastModified: 10,
+    libraryName: 'experiment-node-server',
+    libraryVersion: PACKAGE_VERSION,
+    maxCohortSize: 10,
+    timeoutMillis: COHORT_CONFIG_TIMEOUT,
+  });
+});
+
 test('cohort fetch twice on same cohortId uses same promise and make only one request', async () => {
   const cohortApiGetCohortSpy = jest.spyOn(SdkCohortApi.prototype, 'getCohort');
   cohortApiGetCohortSpy.mockImplementation(async (options) => {