func ExampleLogger() {
var buf bytes.Buffer
logger := log.New(&buf, "logger: ", log.Lshortfile)
logger.Print("Hello, log file!")
fmt.Print(&buf)
// Output:
// logger: example_test.go:17: Hello, log file!
}
func TestWriteToWithLog(t *testing.T) {
defer remove(t, "log.txt")
os.Remove("log.txt")
l := log.New(nil, "", 0)
defer WriteToWithLog("log.txt", l).Close()
want := "some log\n"
l.Println("some log")
fmt.Fprintln(os.Stdout, "This is from stdout")
fmt.Fprintln(os.Stderr, "This is from stderr")
got := readFile(t, "log.txt")
if got != want {
t.Errorf("\nwant: '%s'\n got: '%s'", want, got)
}
}
func TestRotateWithLog(t *testing.T) {
os.Remove("log.txt")
os.Remove("log.txt.old")
l := log.New(nil, "", 0)
stdout := os.Stdout
stderr := os.Stderr
defer remove(t, "log.txt", "log.txt.old")
rl := WriteToWithLog("log.txt", l)
defer rl.Close()
l.Println("some log")
err := os.Rename("log.txt", "log.txt.old")
if err != nil {
os.Stdout = stdout
os.Stderr = stderr
t.Fatalf("TestRotate(): %v\n", err)
}
l.Println("new filename")
got := readFile(t, "log.txt.old")
want := "some log\nnew filename\n"
if got != want {
t.Errorf("log file renamed failed\nwant: '%s'\n got: '%v'", want, got)
}
rl.rotate()
want = "This is after rotation\n"
l.Printf(want)
os.Stdout = stdout
os.Stderr = stderr
got = readFile(t, "log.txt")
if got != want {
t.Errorf("rotate() failed\nwant: '%s'\n got: '%v'", want, got)
}
}