test: add test coverage to the healthcheck route

.emdaer/docs/notes.md

@@ -17,3 +17,4 @@ just meant to save ideas for documentation to process some other time._
 - Filter requests that the CMS should not be bothered with using the resource lists.
 - Make sure to mention that the _Contenta Redis_ module needs to be enabled.
 - Make sure to mention that the /healthckeck is for auto-scaling policies.
+- Create @contentacms/… submodules for logging interfaces like Splunk.

src/routes/healthcheck.test.js

@@ -0,0 +1,22 @@
+// @flow
+
+const healthcheck = require('./healthcheck');
+
+describe('The healthcheck route', () => {
+  test('It responds', () => {
+    const res = {
+      set: jest.fn(),
+      json: jest.fn(),
+    };
+    healthcheck(null, res);
+    expect(res.set).toHaveBeenCalledWith(
+      'Cache-Control',
+      'private, max-age=0, no-cache'
+    );
+    expect(res.json).toHaveBeenCalledWith({
+      meta: {
+        healthcheck: 'good',
+      },
+    });
+  });
+});