Fix another race condition in TestWebhook

There's the potential for a race condition where we try to read the logs
buffer before the logs have been flushed by the webhook process. Kill
the process to flush the logs before testing against the log buffer.

webhook_test.go

@@ -74,6 +74,9 @@ func TestWebhook(t *testing.T) {
 		configPath, cleanupConfigFn := genConfig(t, hookecho, hookTmpl)
 		defer cleanupConfigFn()
 
+		for _, tt := range hookHandlerTests {
+			t.Run(tt.desc, func(t *testing.T) {
+
 				ip, port := serverAddress(t)
 				args := []string{fmt.Sprintf("-hooks=%s", configPath), fmt.Sprintf("-ip=%s", ip), fmt.Sprintf("-port=%s", port), "-verbose"}
 
@@ -91,9 +94,6 @@ func TestWebhook(t *testing.T) {
 
 				waitForServerReady(t, ip, port)
 
-		for _, tt := range hookHandlerTests {
-			t.Run(tt.desc, func(t *testing.T) {
-
 				url := fmt.Sprintf("http://%s:%s/hooks/%s", ip, port, tt.id)
 
 				req, err := http.NewRequest("POST", url, ioutil.NopCloser(strings.NewReader(tt.body)))
@@ -130,15 +130,19 @@ func TestWebhook(t *testing.T) {
 				}
 
 				if tt.logMatch == "" {
-					b.Reset()
 					return
 				}
 
+				// There's the potential for a race condition below where we
+				// try to read the logs buffer b before the logs have been
+				// flushed by the webhook process. Kill the process to flush
+				// the logs.
+				killAndWait(cmd)
+
 				matched, _ := regexp.MatchString(tt.logMatch, b.String())
 				if !matched {
-					t.Fatalf("Unexpected log output:\n%s", b)
+					t.Errorf("failed log match for %q (id: %s):\nmatch pattern: %q\ngot:\n%s", tt.desc, tt.id, tt.logMatch, b)
 				}
-				b.Reset()
 			})
 		}
 	}
@@ -267,6 +271,10 @@ func waitForServer(t *testing.T, url string, status int, timeout time.Duration)
 }
 
 func killAndWait(cmd *exec.Cmd) {
+	if cmd == nil || cmd.ProcessState != nil && cmd.ProcessState.Exited() {
+		return
+	}
+
 	cmd.Process.Kill()
 	cmd.Wait()
 }