You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: internal_vm_test.go
    path of file: ./repos/gitkube/vendor/google.golang.org/appengine/internal
    
    the code of the file until where you have to start completion: // Copyright 2014 Google Inc. All rights reserved.
// Use of this source code is governed by the Apache 2.0
// license that can 
    
func TestInstallingHealthChecker(t *testing.T) {
	try := func(desc string, mux *http.ServeMux, wantCode int, wantBody string) {
		installHealthChecker(mux)
		srv := httptest.NewServer(mux)
		defer srv.Close()

		resp, err := http.Get(srv.URL + "/_ah/health")
		if err != nil {
			t.Errorf("%s: http.Get: %v", desc, err)
			return
		}
		defer resp.Body.Close()
		body, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			t.Errorf("%s: reading body: %v", desc, err)
			return
		}

		if resp.StatusCode != wantCode {
			t.Errorf("%s: got HTTP %d, want %d", desc, resp.StatusCode, wantCode)
			return
		}
		if wantBody != "" && string(body) != wantBody {
			t.Errorf("%s: got HTTP body %q, want %q", desc, body, wantBody)
			return
		}
	}

	// If there's no handlers, or only a root handler, a health checker should be installed.
	try("empty mux", http.NewServeMux(), 200, "ok")
	mux := http.NewServeMux()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		io.WriteString(w, "root handler")
	})
	try("mux with root handler", mux, 200, "ok")

	// If there's a custom health check handler, one should not be installed.
	mux = http.NewServeMux()
	mux.HandleFunc("/_ah/health", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(418)
		io.WriteString(w, "I'm short and stout!")
	})
	try("mux with custom health checker", mux, 418, "I'm short and stout!")
}