Add lock to fake handler to avoid races.

pkg/util/fake_handler.go

@@ -21,12 +21,14 @@ import (
 	"net/http"
 	"net/url"
 	"reflect"
+	"sync"
 )
 
 // TestInterface is a simple interface providing Errorf, to make injection for
 // testing easier (insert 'yo dawg' meme here).
 type TestInterface interface {
 	Errorf(format string, args ...interface{})
+	Logf(format string, args ...interface{})
 }
 
 // LogInterface is a simple interface to allow injection of Logf to report serving errors.
@@ -45,9 +47,21 @@ type FakeHandler struct {
 	// For logging - you can use a *testing.T
 	// This will keep log messages associated with the test.
 	T LogInterface
+
+	// Enforce "only one use" constraint.
+	lock           sync.Mutex
+	requestCount   int
+	hasBeenChecked bool
 }
 
 func (f *FakeHandler) ServeHTTP(response http.ResponseWriter, request *http.Request) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.requestCount++
+	if f.hasBeenChecked {
+		panic("got request after having been validated")
+	}
+
 	f.RequestReceived = request
 	response.WriteHeader(f.StatusCode)
 	response.Write([]byte(f.ResponseBody))
@@ -60,7 +74,14 @@ func (f *FakeHandler) ServeHTTP(response http.ResponseWriter, request *http.Requ
 }
 
 // ValidateRequest verifies that FakeHandler received a request with expected path, method, and body.
-func (f FakeHandler) ValidateRequest(t TestInterface, expectedPath, expectedMethod string, body *string) {
+func (f *FakeHandler) ValidateRequest(t TestInterface, expectedPath, expectedMethod string, body *string) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	if f.requestCount != 1 {
+		t.Logf("Expected 1 call, but got %v. Only the last call is recorded and checked.", f.requestCount)
+	}
+	f.hasBeenChecked = true
+
 	expectURL, err := url.Parse(expectedPath)
 	if err != nil {
 		t.Errorf("Couldn't parse %v as a URL.", expectedPath)

pkg/util/fake_handler_test.go

@@ -72,6 +72,8 @@ func (f *fakeError) Errorf(format string, args ...interface{}) {
 	f.errors = append(f.errors, format)
 }
 
+func (f *fakeError) Logf(format string, args ...interface{}) {}
+
 func TestFakeHandlerWrongPath(t *testing.T) {
 	handler := FakeHandler{}
 	server := httptest.NewServer(&handler)