ipn: tag and test for grinder log lines (#711)

Signed-off-by: Wendi <wendi.yu@yahoo.ca>

tstest/log.go

@@ -7,7 +7,10 @@ package tstest
 import (
 	"log"
 	"os"
+	"sync"
 	"testing"
+
+	"tailscale.com/types/logger"
 )
 
 type testLogWriter struct {
@@ -41,3 +44,48 @@ func (panicLogWriter) Write(b []byte) (int, error) {
 func PanicOnLog() {
 	log.SetOutput(panicLogWriter{})
 }
+
+// ListenFor produces a LogListener wrapping a given logf with the given logStrings
+func ListenFor(logf logger.Logf, logStrings []string) *LogListener {
+	ret := LogListener{
+		logf:      logf,
+		listenFor: logStrings,
+		seen:      make(map[string]bool),
+	}
+	for _, line := range logStrings {
+		ret.seen[line] = false
+	}
+	return &ret
+}
+
+// LogListener takes a list of log lines to listen for
+type LogListener struct {
+	logf      logger.Logf
+	listenFor []string
+
+	mu   sync.Mutex
+	seen map[string]bool
+}
+
+// Logf records and logs a given line
+func (ll *LogListener) Logf(format string, args ...interface{}) {
+	ll.mu.Lock()
+	if _, ok := ll.seen[format]; ok {
+		ll.seen[format] = true
+	}
+	ll.mu.Unlock()
+	ll.logf(format, args)
+}
+
+// Check returns which lines haven't been logged yet
+func (ll *LogListener) Check() []string {
+	ll.mu.Lock()
+	defer ll.mu.Unlock()
+	var notSeen []string
+	for _, line := range ll.listenFor {
+		if !ll.seen[line] {
+			notSeen = append(notSeen, line)
+		}
+	}
+	return notSeen
+}

tstest/log_test.go

@@ -0,0 +1,46 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tstest
+
+import "testing"
+
+func TestLogListener(t *testing.T) {
+	var (
+		l1 = "line 1: %s"
+		l2 = "line 2: %s"
+		l3 = "line 3: %s"
+
+		lineList = []string{l1, l2}
+	)
+
+	ll := ListenFor(t.Logf, lineList)
+
+	if len(ll.Check()) != len(lineList) {
+		t.Errorf("expected %v, got %v", lineList, ll.Check())
+	}
+
+	ll.Logf(l3, "hi")
+
+	if len(ll.Check()) != len(lineList) {
+		t.Errorf("expected %v, got %v", lineList, ll.Check())
+	}
+
+	ll.Logf(l1, "hi")
+
+	if len(ll.Check()) != len(lineList)-1 {
+		t.Errorf("expected %v, got %v", lineList, ll.Check())
+	}
+
+	ll.Logf(l1, "bye")
+
+	if len(ll.Check()) != len(lineList)-1 {
+		t.Errorf("expected %v, got %v", lineList, ll.Check())
+	}
+
+	ll.Logf(l2, "hi")
+	if ll.Check() != nil {
+		t.Errorf("expected empty list, got ll.Check()")
+	}
+}