eliquious · January 27, 2018 00:41 · Feb 11, 2014
diff --git a/mock.go b/mock.go
@@ -0,0 +1,69 @@
+package httpmock
+
+import (
+	"errors"
+	"net/http"
+)
+
+// Responders are callbacks that receive and http request and return a mocked response.
+type Responder func(*http.Request) (*http.Response, error)
+
+// NoResponderFound is returned when no responders are found for a given HTTP method and URL.
+var NoResponderFound = errors.New("no responder found")
+
+// MockTransport implements http.RoundTripper, which fulfills single http requests issued by
+// an http.Client.  This implementation doesn't actually make the call, instead defering to
+// the registered list of responders.
+type MockTransport struct {
+	FailNoResponder bool
+	responders      map[string]Responder
+}
+
+// RoundTrip is required to implement http.MockTransport.  Instead of fulfilling the given request,
+// the internal list of responders is consulted to handle the request.  If no responder is found
+// an error is returned, which is the equivalent of a network error.
+func (m *MockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	key := req.Method + " " + req.URL.String()
+
+	// scan through the responders and find one that matches our key
+	for k, r := range m.responders {
+		if k != key {
+			continue
+		}
+		return r(req)
+	}
+
+	// if we've been told to error when no match was found
+	if m.FailNoResponder {
+		return nil, NoResponderFound
+	}
+
+	// fallback to the default roundtripper
+	return http.DefaultTransport.RoundTrip(req)
+}
+
+// RegisterResponder adds a new responder, associated with a given HTTP method and URL.  When a
+// request comes in that matches, the responder will be called and the response returned to the client.
+func (m *MockTransport) RegisterResponder(method, url string, responder Responder) {
+	m.responders[method+" "+url] = responder
+}
+
+// DefaultMockTransport allows users to easily and globally alter the default RoundTripper for
+// all http requests.
+var DefaultMockTransport = &MockTransport{}
+
+// Activate replaces the `Transport` on the `http.DefaultClient` with our `DefaultMockTransport`.
+func Activate(failNoResponder bool) {
+	DefaultMockTransport.FailNoResponder = failNoResponder
+	http.DefaultClient.Transport = DefaultMockTransport
+}
+
+// Deactivate replaces our `DefaultMockTransport` with the `http.DefaultTransport`.
+func Deactivate() {
+	http.DefaultClient.Transport = http.DefaultTransport
+}
+
+// RegisterResponder adds a responder to the `DefaultMockTransport` responder table.
+func RegisterResponder(method, url string, responder Responder) {
+	DefaultMockTransport.RegisterResponder(method, url, responder)
+}