diff --git a/response.go b/response.go
index 1394ec7..5f3b268 100644
--- a/response.go
+++ b/response.go
@@ -4,8 +4,11 @@ import (
 	"bytes"
 	"encoding/json"
 	"encoding/xml"
+	"errors"
+	"fmt"
 	"io"
 	"net/http"
+	"runtime"
 	"strconv"
 	"strings"
 )
@@ -29,6 +32,68 @@ func NewErrorResponder(err error) Responder {
 	}
 }
 
+// NewNotFoundResponder creates a Responder typically used in
+// conjunction with RegisterNoResponder() function and testing
+// package, to be proactive when a Responder is not found. fn is
+// called with a unique string parameter containing the name of the
+// missing route and the stack trace to localize the origin of the
+// call. If fn returns (= if it does not panic), the responder returns
+// an error of the form: "Responder not found for GET http://foo.bar/path".
+// Note that fn can be nil.
+//
+// It is useful when writing tests to ensure that all routes have been
+// mocked.
+//
+// Example of use:
+//   import "testing"
+//   ...
+//   func TestMyApp(t *testing.T) {
+//   	...
+//   	// Calls testing.Fatal with the name of Responder-less route and
+//   	// the stack trace of the call.
+//   	httpmock.RegisterNoResponder(httpmock.NewNotFoundResponder(t.Fatal))
+//
+// Will abort the current test and print something like:
+//   response:69: Responder not found for: GET http://foo.bar/path
+//       Called from goroutine 20 [running]:
+//         github.com/jarcoal/httpmock.NewNotFoundResponder.func1(0xc00011f000, 0x0, 0x42dfb1, 0x77ece8)
+//           /go/src/github.com/jarcoal/httpmock/response.go:67 +0x1c1
+//         github.com/jarcoal/httpmock.runCancelable(0xc00004bfc0, 0xc00011f000, 0x7692f8, 0xc, 0xc0001208b0)
+//           /go/src/github.com/jarcoal/httpmock/transport.go:146 +0x7e
+//         github.com/jarcoal/httpmock.(*MockTransport).RoundTrip(0xc00005c980, 0xc00011f000, 0xc00005c980, 0x0, 0x0)
+//           /go/src/github.com/jarcoal/httpmock/transport.go:140 +0x19d
+//         net/http.send(0xc00011f000, 0x7d3440, 0xc00005c980, 0x0, 0x0, 0x0, 0xc000010400, 0xc000047bd8, 0x1, 0x0)
+//           /usr/local/go/src/net/http/client.go:250 +0x461
+//         net/http.(*Client).send(0x9f6e20, 0xc00011f000, 0x0, 0x0, 0x0, 0xc000010400, 0x0, 0x1, 0x9f7ac0)
+//         	 /usr/local/go/src/net/http/client.go:174 +0xfb
+//         net/http.(*Client).do(0x9f6e20, 0xc00011f000, 0x0, 0x0, 0x0)
+//         	 /usr/local/go/src/net/http/client.go:641 +0x279
+//         net/http.(*Client).Do(...)
+//         	 /usr/local/go/src/net/http/client.go:509
+//         net/http.(*Client).Get(0x9f6e20, 0xc00001e420, 0x23, 0xc00012c000, 0xb, 0x600)
+//         	 /usr/local/go/src/net/http/client.go:398 +0x9e
+//         net/http.Get(...)
+//         	 /usr/local/go/src/net/http/client.go:370
+//         foo.bar/foobar/foobar.TestMyApp(0xc00011e000)
+//         	 /go/src/foo.bar/foobar/foobar/my_app_test.go:272 +0xdbb
+//         testing.tRunner(0xc00011e000, 0x77e3a8)
+//         	 /usr/local/go/src/testing/testing.go:865 +0xc0
+//         created by testing.(*T).Run
+//         	 /usr/local/go/src/testing/testing.go:916 +0x35a
+func NewNotFoundResponder(fn func(...interface{})) Responder {
+	return func(req *http.Request) (*http.Response, error) {
+		mesg := fmt.Sprintf("Responder not found for %s %s", req.Method, req.URL)
+		if fn != nil {
+			buf := make([]byte, 4096)
+			n := runtime.Stack(buf, false)
+			buf = buf[:n]
+			fn(mesg + "\nCalled from " +
+				strings.Replace(strings.TrimSuffix(string(buf), "\n"), "\n", "\n  ", -1))
+		}
+		return nil, errors.New(mesg)
+	}
+}
+
 // NewStringResponse creates an *http.Response with a body based on the given string.  Also accepts
 // an http status code.
 func NewStringResponse(status int, body string) *http.Response {
diff --git a/response_test.go b/response_test.go
index f0835ef..a99480a 100644
--- a/response_test.go
+++ b/response_test.go
@@ -4,8 +4,10 @@ import (
 	"encoding/json"
 	"encoding/xml"
 	"errors"
+	"fmt"
 	"io/ioutil"
 	"net/http"
+	"strings"
 	"testing"
 )
 
@@ -48,6 +50,54 @@ func TestResponderFromResponse(t *testing.T) {
 	}
 }
 
+func TestNewNotFoundResponder(t *testing.T) {
+	var mesg string
+	responder := NewNotFoundResponder(func(args ...interface{}) {
+		mesg = fmt.Sprint(args[0])
+	})
+
+	req, err := http.NewRequest("GET", "http://foo.bar/path", nil)
+	if err != nil {
+		t.Fatal("Error creating request")
+	}
+
+	const title = "Responder not found for GET http://foo.bar/path"
+
+	resp, err := responder(req)
+	if resp != nil {
+		t.Error("resp should be nil")
+	}
+	if err == nil {
+		t.Error("err should be not nil")
+	} else if err.Error() != title {
+		t.Errorf(`err mismatch, got: "%s", expected: "%s"`,
+			err.Error(),
+			"Responder not found for: GET http://foo.bar/path")
+	}
+
+	if !strings.HasPrefix(mesg, title+"\nCalled from ") {
+		t.Error(`mesg should begin with "` + title + `\nCalled from ", but it is: "` + mesg + `"`)
+	}
+	if strings.HasSuffix(mesg, "\n") {
+		t.Error(`mesg should not end with \n, but it is: "` + mesg + `"`)
+	}
+
+	// nil fn
+	responder = NewNotFoundResponder(nil)
+
+	resp, err = responder(req)
+	if resp != nil {
+		t.Error("resp should be nil")
+	}
+	if err == nil {
+		t.Error("err should be not nil")
+	} else if err.Error() != title {
+		t.Errorf(`err mismatch, got: "%s", expected: "%s"`,
+			err.Error(),
+			"Responder not found for: GET http://foo.bar/path")
+	}
+}
+
 func TestNewStringResponse(t *testing.T) {
 	body := "hello world"
 	status := 200