Improve test logger (#24235)

Before, there was a `log/buffer.go`, but that design is not general, and
it introduces a lot of irrelevant `Content() (string, error) ` and
`return "", fmt.Errorf("not supported")` .


And the old `log/buffer.go` is difficult to use, developers have to
write a lot of `Contains` and `Sleep` code.


The new `LogChecker` is designed to be a general approach to help to
assert some messages appearing or not appearing in logs.

modules/test/logchecker_test.go

@@ -0,0 +1,47 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package test
+
+import (
+	"testing"
+	"time"
+
+	"code.gitea.io/gitea/modules/log"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLogChecker(t *testing.T) {
+	_ = log.NewLogger(1000, "console", "console", `{"level":"info","stacktracelevel":"NONE","stderr":true}`)
+
+	lc, cleanup := NewLogChecker(log.DEFAULT)
+	defer cleanup()
+
+	lc.Filter("First", "Third").StopMark("End")
+	log.Info("test")
+
+	filtered, stopped := lc.Check(100 * time.Millisecond)
+	assert.EqualValues(t, []bool{false, false}, filtered)
+	assert.EqualValues(t, false, stopped)
+
+	log.Info("First")
+	filtered, stopped = lc.Check(100 * time.Millisecond)
+	assert.EqualValues(t, []bool{true, false}, filtered)
+	assert.EqualValues(t, false, stopped)
+
+	log.Info("Second")
+	filtered, stopped = lc.Check(100 * time.Millisecond)
+	assert.EqualValues(t, []bool{true, false}, filtered)
+	assert.EqualValues(t, false, stopped)
+
+	log.Info("Third")
+	filtered, stopped = lc.Check(100 * time.Millisecond)
+	assert.EqualValues(t, []bool{true, true}, filtered)
+	assert.EqualValues(t, false, stopped)
+
+	log.Info("End")
+	filtered, stopped = lc.Check(100 * time.Millisecond)
+	assert.EqualValues(t, []bool{true, true}, filtered)
+	assert.EqualValues(t, true, stopped)
+}