Add unit test

x-pack/plugins/security_solution/public/detections/components/rules/step_about_rule/field_validators.test.ts

@@ -0,0 +1,37 @@
+/*
+ * 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 { ValidationFuncArg } from 'src/plugins/es_ui_shared/static/forms/hook_form_lib';
+
+import { emptyArrayItem } from './field_validators';
+
+describe('emptyArrayItem', () => {
+  const MESSAGE = 'error message';
+  const defaultArgs: ValidationFuncArg<FormData, unknown> = {
+    path: '',
+    form: {
+      getFormData: jest.fn(),
+      getFields: jest.fn(),
+    },
+    formData: {} as FormData,
+    errors: [],
+    value: undefined,
+  };
+
+  test('should return an error when value is an empty string', () => {
+    expect(emptyArrayItem(MESSAGE)({ ...defaultArgs, value: '    ' })).toEqual({
+      code: 'ERR_INVALID_CHARS',
+      message: MESSAGE,
+    });
+  });
+  test('should return undefined when value is not a string', () => {
+    expect(emptyArrayItem(MESSAGE)({ ...defaultArgs, value: 9999 })).toBe(undefined);
+  });
+  test('should return undefined when value is not an empty string', () => {
+    expect(emptyArrayItem(MESSAGE)({ ...defaultArgs, value: 'non-empty string' })).toBe(undefined);
+  });
+});