Add tests for WithFileOutput

logp/core_test.go

@@ -18,8 +18,12 @@
 package logp
 
 import (
+	"encoding/json"
 	"io/ioutil"
 	golog "log"
+	"os"
+	"path/filepath"
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -212,3 +216,117 @@ func TestLoggingECSFields(t *testing.T) {
 		}
 	}
 }
+
+func TestWithFileOutput(t *testing.T) {
+	var tempDir1, tempDir2 string
+	// Because of the way logp and zap work, when the test finishes, the log
+	// file is still open, this creates a problem on Windows because the
+	// temporary directory cannot be removed if a file inside it is still
+	// open.
+	//
+	// To circumvent this problem on Windows we use os.MkdirTemp
+	// leaving it behind and delegating to the OS the responsibility
+	// of cleaning it up (usually on restart).
+	if runtime.GOOS == "windows" {
+		var err error
+		tempDir1, err = os.MkdirTemp("", t.Name()+"-*")
+		if err != nil {
+			t.Fatalf("could not create temporary directory: %s", err)
+		}
+		tempDir2, err = os.MkdirTemp("", t.Name()+"-*")
+		if err != nil {
+			t.Fatalf("could not create temporary directory: %s", err)
+		}
+	} else {
+		// We have no problems on Linux and Darwin, so we can rely on t.TempDir
+		// that will remove the files once the tests finishes.
+		tempDir1 = t.TempDir()
+		tempDir2 = t.TempDir()
+	}
+
+	expectedLogMessage := "this is a log message"
+	expectedLogLogger := t.Name() + "-second"
+
+	// We follow the same approach as on a Beat, first the logger
+	// (always global) is configured and used, then we instantiate
+	// a new one, secondLogger, and perform the tests on it.
+	loggerCfg := DefaultConfig(DefaultEnvironment)
+	loggerCfg.Beat = t.Name() + "-first"
+	loggerCfg.ToFiles = true
+	loggerCfg.ToStderr = false
+	loggerCfg.Files.Name = "test-log-file-first"
+	// We want a separate directory for this logger
+	// and we don't need to inspect it.
+	loggerCfg.Files.Path = tempDir1
+
+	// Configures the global logger with the "default" log configuration.
+	if err := Configure(loggerCfg); err != nil {
+		t.Errorf("could not initialise logger: %s", err)
+	}
+	logger := L()
+
+	// Create a log entry just to "test" the logger
+	logger.Info("not the message we want")
+	if err := logger.Sync(); err != nil {
+		t.Fatalf("could not sync log file from fist logger: %s", err)
+	}
+
+	// Actually clones the logger and use the "WithFileOutput" function
+	secondCfg := DefaultConfig(DefaultEnvironment)
+	secondCfg.ToFiles = true
+	secondCfg.ToStderr = false
+	secondCfg.Files.Name = "test-log-file"
+	secondCfg.Files.Path = tempDir2
+
+	// We do not call Configure here as we do not want to affect
+	// the global logger configuration
+	secondLogger := NewLogger(t.Name() + "-second")
+	secondLogger = secondLogger.WithOptions(zap.WrapCore(WithFileOutput(secondCfg)))
+	secondLogger.Info(expectedLogMessage)
+	if err := secondLogger.Sync(); err != nil {
+		t.Fatalf("could not sync log file from second logger: %s", err)
+	}
+
+	// Writes again with the first logger to ensure it has not been affected
+	// by the new configuration on the second logger.
+	logger.Info("not the message we want")
+	if err := logger.Sync(); err != nil {
+		t.Fatalf("could not sync log file from fist logger: %s", err)
+	}
+
+	// Find the log file. The file name gets the date added, so we list the
+	// directory and ensure there is only one file there.
+	files, err := os.ReadDir(tempDir2)
+	if err != nil {
+		t.Fatalf("could not read temporary directory '%s': %s", tempDir2, err)
+	}
+
+	// If there is more than one file, list all files
+	// and fail the test.
+	if len(files) != 1 {
+		t.Errorf("found %d files in '%s', there must be only one", len(files), tempDir2)
+		t.Errorf("Files in '%s':", tempDir2)
+		for _, f := range files {
+			t.Error(f.Name())
+		}
+		t.FailNow()
+	}
+
+	logData, err := os.ReadFile(filepath.Join(tempDir2, files[0].Name()))
+	if err != nil {
+		t.Fatalf("could not read log file: %s", err)
+	}
+
+	logEntry := map[string]any{}
+	if err := json.Unmarshal(logData, &logEntry); err != nil {
+		t.Fatalf("could not read log entry as JSON. Log entry: '%s'", string(logData))
+	}
+
+	// Ensure a couple of fields exist
+	if logEntry["log.logger"] != expectedLogLogger {
+		t.Fatalf("expecting 'log.logger' to be '%s', got '%s' instead", expectedLogLogger, logEntry["log.logger"])
+	}
+	if logEntry["message"] != expectedLogMessage {
+		t.Fatalf("expecting 'message' to be '%s, got '%s' instead", expectedLogMessage, logEntry["message"])
+	}
+}