Adds push/pull client functionality

These methods rely on an ObjectStore interface, which is meant to
approximate the storage behavior of the docker engine. This is very much
subject to change.

test/test.go

@@ -0,0 +1,97 @@
+package test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+)
+
+// RequestResponseMap is a mapping from Requests to Responses
+type RequestResponseMap []RequestResponseMapping
+
+// RequestResponseMapping defines an ordered list of Responses to be sent in
+// response to a given Request
+type RequestResponseMapping struct {
+	Request   Request
+	Responses []Response
+}
+
+// TODO(bbland): add support for request headers
+
+// Request is a simplified http.Request object
+type Request struct {
+	// Method is the http method of the request, for example GET
+	Method string
+
+	// Route is the http route of this request
+	Route string
+
+	// Body is the byte contents of the http request
+	Body []byte
+}
+
+func (r Request) String() string {
+	return fmt.Sprintf("%s %s\n%s", r.Method, r.Route, r.Body)
+}
+
+// Response is a simplified http.Response object
+type Response struct {
+	// Statuscode is the http status code of the Response
+	StatusCode int
+
+	// Headers are the http headers of this Response
+	Headers http.Header
+
+	// Body is the response body
+	Body []byte
+}
+
+// testHandler is an http.Handler with a defined mapping from Request to an
+// ordered list of Response objects
+type testHandler struct {
+	responseMap map[string][]Response
+}
+
+// NewHandler returns a new test handler that responds to defined requests
+// with specified responses
+// Each time a Request is received, the next Response is returned in the
+// mapping, until no Responses are defined, at which point a 404 is sent back
+func NewHandler(requestResponseMap RequestResponseMap) http.Handler {
+	responseMap := make(map[string][]Response)
+	for _, mapping := range requestResponseMap {
+		responseMap[mapping.Request.String()] = mapping.Responses
+	}
+	return &testHandler{responseMap: responseMap}
+}
+
+func (app *testHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	defer r.Body.Close()
+
+	requestBody, _ := ioutil.ReadAll(r.Body)
+	request := Request{
+		Method: r.Method,
+		Route:  r.URL.Path,
+		Body:   requestBody,
+	}
+
+	responses, ok := app.responseMap[request.String()]
+
+	if !ok || len(responses) == 0 {
+		http.NotFound(w, r)
+		return
+	}
+
+	response := responses[0]
+	app.responseMap[request.String()] = responses[1:]
+
+	responseHeader := w.Header()
+	for k, v := range response.Headers {
+		responseHeader[k] = v
+	}
+
+	w.WriteHeader(response.StatusCode)
+
+	io.Copy(w, bytes.NewReader(response.Body))
+}