A very rugged way to do some mock endpoints with routes.

example_test.go

package example

import (
	"testing"
	"net/http/httptest"
	"net/http"
	"fmt"
	"io/ioutil"
)

// mockHandler implements http.Handler and is used to mock 3rd party
// endpoints.
//
// routes is a basic router implementation to make testing a bit easier to implement.
type mockHandler struct {
	routes map[string]func(http.ResponseWriter, *http.Request)
}

// mockRouter is an instance of mockHandler and is used in our tests to add new routes
// to test.
var mockRouter = &mockHandler{
	routes: make(map[string]func(http.ResponseWriter, *http.Request)),
}

// mockServer is an instance of a httpstest.Server and used to stub out the 3rd party endpoints.
var mockServer = httptest.NewServer(mockRouter)

// ServerHTTP implements the requirements for an http.Handler.
func (m mockHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	route := r.URL.String() + ":" + r.Method
	if m.routes[route] != nil {
		m.routes[route](w, r)
	} else {
		fmt.Fprint(w, "unknown route")
	}
}

// Dynamically add new routes to ServeHTTP via the routes map.
func (m *mockHandler) HandleFunc(route, method string, f func(http.ResponseWriter, *http.Request)) {
	m.routes[route + ":" + method] = f
}