Ghttp

ghttp: testing HTTP clients

ghttp spins up a real test HTTP server so you can exercise code that makes outbound HTTP requests (clients, SDKs, anything calling net/http). You register handlers that assert on the incoming request and return a canned response; the server records every request it receives. It wraps net/http/httptest.

import (
	. "github.com/onsi/gomega"
	"github.com/onsi/gomega/ghttp"
	"net/http"
)

This skill assumes a dot-import of gomega. Docs: https://onsi.github.io/gomega/#ghttp-testing-http-clients. See gomega:matchers for the matchers used in assertions and gomega:async if the client is non-blocking.

Lifecycle

server := ghttp.NewServer()          // or ghttp.NewTLSServer()
defer server.Close()                 // ALWAYS defer Close

client := myapi.NewClient(server.URL())   // URL is random per run — inject it

The server URL is auto-generated and varies between runs, so you must inject server.URL() into the code under test rather than hard-coding it. With Ginkgo, server = ghttp.NewServer() in BeforeEach and server.Close() in AfterEach.

The handler model

server.AppendHandlers(handlers...) registers an ordered list of handlers, one per expected request. The first request is matched against the first handler, the second against the second, and so on. A handler is just an http.HandlerFunc.

server.AppendHandlers(
	ghttp.VerifyRequest("GET", "/sprockets"),
)

Gotchas (the core mental model):

• AppendHandlers is strictly ordered. Requests must arrive in exactly the registered order.
• Each handler handles exactly one request. To run several checks against a single request, combine them with ghttp.CombineHandlers (below).
• The request count is asserted by default. If the client sends more requests than there are handlers (or hits an unregistered route), the test fails. Guard the trivial false-positive (client made no request) with Expect(server.ReceivedRequests()).To(HaveLen(1)).

Verifying the incoming request

These return handlers that fail the test if the request doesn't match:

ghttp.VerifyRequest("GET", "/sprockets")                       // method + path
ghttp.VerifyRequest("GET", "/sprockets", "category=encabulators") // + RawQuery
ghttp.VerifyHeader(http.Header{"X-API-Version": []string{"1.0"}})
ghttp.VerifyHeaderKV("X-API-Version", "1.0")                   // convenience for one key
ghttp.VerifyContentType("application/json")
ghttp.VerifyBasicAuth("gopher", "tacoshell")
ghttp.VerifyBody([]byte("raw body"))
ghttp.VerifyJSON(`{"name":"foo"}`)                             // semantic JSON compare
ghttp.VerifyJSONRepresenting(Sprocket{Name: "foo"})           // marshal obj, then compare
ghttp.VerifyForm(url.Values{"q": []string{"x"}})              // parsed form values
ghttp.VerifyFormKV("q", "x")                                  // convenience for one key

The path argument to VerifyRequest accepts a string or a *regexp.Regexp. You can write your own verify handler — pass any http.HandlerFunc that makes assertions against the *http.Request.

Combining handlers for one request

ghttp.CombineHandlers(...) wraps several handlers into one handler so they all run against a single request. Pass that one wrapper to AppendHandlers. This is how you assert on a request and respond:

server.AppendHandlers(
	ghttp.CombineHandlers(
		ghttp.VerifyRequest("GET", "/sprockets", "category=encabulators"),
		ghttp.VerifyBasicAuth(username, password),
		ghttp.VerifyHeaderKV("X-API-Version", "1.0"),
		ghttp.RespondWithJSONEncoded(http.StatusOK, sprockets),
	),
)

Providing responses

ghttp.RespondWith(http.StatusOK, `[{"name":"foo"}]`)          // status + body (+ optional http.Header)
ghttp.RespondWith(http.StatusOK, body, http.Header{"X-Foo": []string{"bar"}})
ghttp.RespondWithJSONEncoded(http.StatusOK, anyObject)        // JSON-encodes the object for you
ghttp.RespondWithJSONEncodedPtr(&statusCode, &object)         // reads through pointers at request time
ghttp.RespondWithPtr(&statusCode, &body)

End-to-end example

var server *ghttp.Server
var client *sprockets.Client

BeforeEach(func() {
	server = ghttp.NewServer()
	client = sprockets.NewClient(server.URL())
})
AfterEach(func() { server.Close() })

It("fetches sprockets", func() {
	returned := []Sprocket{{Name: "entropic decoupler", Color: "red"}}
	server.AppendHandlers(
		ghttp.CombineHandlers(
			ghttp.VerifyRequest("GET", "/sprockets", "category=encabulators"),
			ghttp.VerifyHeaderKV("X-API-Version", "1.0"),
			ghttp.RespondWithJSONEncoded(http.StatusOK, returned),
		),
	)

	sprockets, err := client.FetchSprockets("encabulators")
	Expect(err).NotTo(HaveOccurred())
	Expect(sprockets).To(Equal(returned))
	Expect(server.ReceivedRequests()).To(HaveLen(1))
})

Testing different response scenarios

To exercise 200/401/404 against the same handler setup, capture a status (and/or body) variable in a closure via the *Ptr responders and mutate it per sub-context. The pointer is dereferenced when the request arrives:

var statusCode int
var returned []Sprocket

BeforeEach(func() {
	server.AppendHandlers(ghttp.CombineHandlers(
		ghttp.VerifyRequest("GET", "/sprockets"),
		ghttp.RespondWithJSONEncodedPtr(&statusCode, &returned),
	))
})

Context("when unauthorized", func() {
	BeforeEach(func() { statusCode = http.StatusUnauthorized })
	It("errors", func() {
		_, err := client.FetchSprockets("")
		Expect(err).To(MatchError(SprocketsErrorUnauthorized))
	})
})

Handling multiple requests

Pass multiple handlers to AppendHandlers for clients that make several requests (e.g. pagination). They're consumed in order:

server.AppendHandlers(
	ghttp.CombineHandlers(
		ghttp.VerifyRequest("GET", "/sprockets", "category=encabulators"),
		ghttp.RespondWithJSONEncoded(http.StatusOK, firstPage),
	),
	ghttp.CombineHandlers(
		ghttp.VerifyRequest("GET", "/sprockets", "category=encabulators&pagination-token=next"),
		ghttp.RespondWithJSONEncoded(http.StatusOK, secondPage),
	),
)

Because the server fails when requests exceed handlers, this also asserts the client stops after the last page.

Mutating registered handlers by index

server.SetHandler(0, newHandler)            // replace handler at index
h := server.GetHandler(0)                   // read it back
server.WrapHandler(0, extraVerifyHandler)   // run an extra handler around the existing one

MUXing unordered routes

AppendHandlers is for ordered assertions. When requests can arrive in any order or any number of times, use server.RouteToHandler(method, path, handler) instead. The path is a string or a *regexp.Regexp.

server.RouteToHandler("POST", "/login", ghttp.CombineHandlers(
	ghttp.VerifyRequest("POST", "/login", "user=bob&password=password"),
	ghttp.RespondWith(http.StatusOK, "your-auth-token"),
))

Routing precedence: on each request the server first checks RouteToHandler routes; if none match it pops the next AppendHandlers handler; if that stack is empty it consults the unhandled-request policy below. You can mix both: ordered assertions via AppendHandlers for the requests you care about, MUXed routes for incidental traffic (auth, health checks) that interleaves.

Allowing unhandled requests

By default an unhandled request fails the test. To return a fixed status instead:

server.SetAllowUnhandledRequests(true)
server.SetUnhandledRequestStatusCode(http.StatusOK) // default would be 500

Unhandled requests are still recorded in server.ReceivedRequests(), so you can assert on them after the fact.

Escape hatches

• server.HTTPTestServer is the underlying *httptest.Server — use it for custom listeners (via ghttp.NewUnstartedServer() + server.Start()), TLS config, or anything ghttp doesn't wrap.
• server.RoundTripper(rt) returns an http.RoundTripper that redirects requests to the test server. Use it when you must hand a configured *http.Client to the code under test rather than a URL. Pass nil to use http.DefaultTransport:

httpClient := &http.Client{Transport: server.RoundTripper(nil)}