add unit tests for getHelpText utility function

Author: couvq

x-pack/platform/plugins/shared/streams_app/public/components/data_management/stream_detail_routing/get_help_text.test.ts

@@ -0,0 +1,31 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { getHelpText } from './stream_name_form_row';
+
+const prefix = 'logs.';
+
+describe('getHelpText', () => {
+  it('should return empty error help text when stream name is shorter than the prefix', () => {
+    const streamNameWithEmptyChildName = 'logs.';
+    const result = getHelpText(prefix, streamNameWithEmptyChildName, false);
+    expect(result).toBe('Stream name must not be empty.');
+  });
+
+  it('should return name too long error help text when stream name is longer than 200 characters', () => {
+    const streamNameLongerThan200Chars =
+      'logs.xwdaqmsegtkamcrofcfcomnlkkkrkqtlkbqizvjvtrbwereqygqaaxmodzccqipzpwymyowrtvljtxevczoohrbpgijilsdptszgssmrkpwhvkukkgiqhvmcuzygmolyyadbxwngbkqjkretmzhgntkjkhrmltgyurufizwlelvmaqtngwhwqhxpfsuxiivxspvtwfcem';
+    const result = getHelpText(prefix, streamNameLongerThan200Chars, false);
+    expect(result).toBe('Stream name cannot be longer than 200 characters.');
+  });
+
+  it('should return undefined help text when input is valid', () => {
+    const validStreamName = 'logs.multiplayer';
+    const result = getHelpText(prefix, validStreamName, false);
+    expect(result).toBeUndefined();
+  });
+});

x-pack/platform/plugins/shared/streams_app/public/components/data_management/stream_detail_routing/stream_name_form_row.tsx

@@ -30,8 +30,11 @@ const MIN_NAME_LENGTH = 1;
 const MAX_NAME_LENGTH = 200;
 const PREFIX_MAX_VISIBLE_CHARACTERS = 25;
 
-// TODO: write a unit test for this function
-const getHelpText = (prefix: string, value: string, readOnly: boolean): string | undefined => {
+export const getHelpText = (
+  prefix: string,
+  value: string,
+  readOnly: boolean
+): string | undefined => {
   if (value.length <= prefix.length && !readOnly) {
     return i18n.translate('xpack.streams.streamDetailRouting.emptyNameErrorHelpText', {
       defaultMessage: 'Stream name must not be empty.',