diff --git a/x-pack/plugins/enterprise_search/server/routes/app_search/engines.test.ts b/x-pack/plugins/enterprise_search/server/routes/app_search/engines.test.ts
new file mode 100644
index 0000000000000..608d79f0cdbcf
--- /dev/null
+++ b/x-pack/plugins/enterprise_search/server/routes/app_search/engines.test.ts
@@ -0,0 +1,171 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { RequestHandlerContext } from 'kibana/server';
+import { mockRouter, RouterMock } from 'src/core/server/http/router/router.mock';
+import { httpServerMock } from 'src/core/server/http/http_server.mocks';
+import { RouteValidatorConfig } from 'src/core/server/http/router/validator';
+
+import { registerEnginesRoute } from './engines';
+import { ObjectType } from '@kbn/config-schema';
+
+jest.mock('node-fetch');
+const fetch = jest.requireActual('node-fetch');
+const { Response } = fetch;
+const fetchMock = require('node-fetch') as jest.Mocked<typeof fetch>;
+
+describe('engine routes', () => {
+  describe('GET /api/app_search/engines', () => {
+    const AUTH_HEADER = 'Basic 123';
+    let router: RouterMock;
+    const mockResponseFactory = httpServerMock.createResponseFactory();
+
+    beforeEach(() => {
+      jest.resetAllMocks();
+      router = mockRouter.create();
+      registerEnginesRoute({
+        router,
+        config: {
+          host: 'http://localhost:3002',
+        },
+      });
+    });
+
+    describe('when the underlying App Search API returns a 200', () => {
+      beforeEach(() => {
+        AppSearchAPI.shouldBeCalledWith(
+          `http://localhost:3002/as/engines/collection?type=indexed&page[current]=1&page[size]=10`,
+          {
+            headers: { Authorization: AUTH_HEADER },
+          }
+        ).andReturn({ name: 'engine1' });
+      });
+
+      it('should return 200 with a list of engines from the App Search API', async () => {
+        await callThisRoute();
+
+        expectResponseToBe200With({
+          body: { name: 'engine1' },
+          headers: { 'content-type': 'application/json' },
+        });
+      });
+    });
+
+    describe('when the underlying App Search API redirects to /login', () => {
+      beforeEach(() => {
+        AppSearchAPI.shouldBeCalledWith(
+          `http://localhost:3002/as/engines/collection?type=indexed&page[current]=1&page[size]=10`,
+          {
+            headers: { Authorization: AUTH_HEADER },
+          }
+        ).andReturnRedirect();
+      });
+
+      it('should return 200 with a message', async () => {
+        await callThisRoute();
+
+        expectResponseToBe200With({
+          body: { message: 'no-as-account' },
+          headers: { 'content-type': 'application/json' },
+        });
+      });
+    });
+
+    describe('validation', () => {
+      function itShouldValidate(request: { query: object }) {
+        it('should be validated', async () => {
+          expect(() => executeRouteValidation(request)).not.toThrow();
+        });
+      }
+
+      function itShouldThrow(request: { query: object }) {
+        it('should throw', async () => {
+          expect(() => executeRouteValidation(request)).toThrow();
+        });
+      }
+
+      describe('when query is valid', () => {
+        const request = { query: { type: 'indexed', pageIndex: 1 } };
+        itShouldValidate(request);
+      });
+
+      describe('pageIndex is wrong type', () => {
+        const request = { query: { type: 'indexed', pageIndex: 'indexed' } };
+        itShouldThrow(request);
+      });
+
+      describe('type is wrong type', () => {
+        const request = { query: { type: 1, pageIndex: 1 } };
+        itShouldThrow(request);
+      });
+
+      describe('pageIndex is missing', () => {
+        const request = { query: { type: 'indexed' } };
+        itShouldThrow(request);
+      });
+
+      describe('type is missing', () => {
+        const request = { query: { pageIndex: 1 } };
+        itShouldThrow(request);
+      });
+    });
+
+    const AppSearchAPI = {
+      shouldBeCalledWith(expectedUrl: string, expectedParams: object) {
+        return {
+          andReturnRedirect() {
+            fetchMock.mockImplementation((url: string, params: object) => {
+              expect(url).toEqual(expectedUrl);
+              expect(params).toEqual(expectedParams);
+
+              return Promise.resolve(
+                new Response('{}', {
+                  url: '/login',
+                })
+              );
+            });
+          },
+          andReturn(response: object) {
+            fetchMock.mockImplementation((url: string, params: object) => {
+              expect(url).toEqual(expectedUrl);
+              expect(params).toEqual(expectedParams);
+
+              return Promise.resolve(new Response(JSON.stringify(response)));
+            });
+          },
+        };
+      },
+    };
+
+    const expectResponseToBe200With = (response: object) => {
+      expect(mockResponseFactory.ok).toHaveBeenCalledWith(response);
+    };
+
+    const callThisRoute = async (
+      request = {
+        headers: {
+          authorization: AUTH_HEADER,
+        },
+        query: {
+          type: 'indexed',
+          pageIndex: 1,
+        },
+      }
+    ) => {
+      const [_, handler] = router.get.mock.calls[0];
+
+      const context = {} as jest.Mocked<RequestHandlerContext>;
+      await handler(context, httpServerMock.createKibanaRequest(request), mockResponseFactory);
+    };
+
+    const executeRouteValidation = (data: { query: object }) => {
+      const [config] = router.get.mock.calls[0];
+      const validate = config.validate as RouteValidatorConfig<{}, {}, {}>;
+      const query = validate.query as ObjectType;
+      query.validate(data.query);
+    };
+  });
+});
diff --git a/x-pack/plugins/enterprise_search/server/routes/app_search/engines.ts b/x-pack/plugins/enterprise_search/server/routes/app_search/engines.ts
index da75815628a88..8455b01aa4354 100644
--- a/x-pack/plugins/enterprise_search/server/routes/app_search/engines.ts
+++ b/x-pack/plugins/enterprise_search/server/routes/app_search/engines.ts
@@ -28,8 +28,7 @@ export function registerEnginesRoute({ router, config }) {
       });
 
       if (enginesResponse.url.endsWith('/login')) {
-        return response.custom({
-          statusCode: 200,
+        return response.ok({
           body: { message: 'no-as-account' },
           headers: { 'content-type': 'application/json' },
         });