Add tests

Author: kalleep

internal/component/loki/source/file/internal/tail/block.go

@@ -101,13 +101,12 @@ func blockUntilEvent(ctx context.Context, f *os.File, prevSize int64, cfg *Confi
 		}
 
 		// File got bigger?
-		if prevSize > 0 && prevSize < currentSize {
+		if prevSize < currentSize {
 			return eventModified, nil
 		}
 
 		// File was appended to (changed)?
-		modTime := fi.ModTime()
-		if modTime != prevModTime {
+		if fi.ModTime() != prevModTime {
 			return eventModified, nil
 		}
 

internal/component/loki/source/file/internal/tail/block_test.go

@@ -0,0 +1,106 @@
+package tail
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBlockUntilEvent(t *testing.T) {
+	watcherConfig := WatcherConfig{
+		MinPollFrequency: 5 * time.Millisecond,
+		MaxPollFrequency: 5 * time.Millisecond,
+	}
+
+	t.Run("should return modified event when file is written to", func(t *testing.T) {
+		f := createEmptyFile(t, "startempty")
+		defer f.Close()
+
+		go func() {
+			time.Sleep(50 * time.Millisecond)
+			_, err := f.WriteString("updated")
+			require.NoError(t, err)
+		}()
+
+		event, err := blockUntilEvent(context.Background(), f, 0, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+		require.Equal(t, eventModified, event)
+	})
+
+	t.Run("should return modified event if mod time is updated", func(t *testing.T) {
+		f := createEmptyFile(t, "startempty")
+		defer f.Close()
+
+		go func() {
+			time.Sleep(50 * time.Millisecond)
+			require.NoError(t, os.Chtimes(f.Name(), time.Now(), time.Now()))
+		}()
+
+		event, err := blockUntilEvent(context.Background(), f, 0, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+		require.Equal(t, eventModified, event)
+	})
+
+	t.Run("should return deleted event if file is deleted", func(t *testing.T) {
+		f := createEmptyFile(t, "startempty")
+		defer f.Close()
+
+		go func() {
+			time.Sleep(50 * time.Millisecond)
+			removeFile(t, f.Name())
+		}()
+
+		event, err := blockUntilEvent(context.Background(), f, 0, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+		require.Equal(t, eventDeleted, event)
+	})
+
+	t.Run("should return deleted event if file is deleted before", func(t *testing.T) {
+		f := createEmptyFile(t, "startempty")
+		defer f.Close()
+
+		removeFile(t, f.Name())
+
+		event, err := blockUntilEvent(context.Background(), f, 0, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+		require.Equal(t, eventDeleted, event)
+	})
+
+	t.Run("should return truncated event", func(t *testing.T) {
+		f := createFileWithContent(t, "truncate", "content")
+		defer f.Close()
+
+		offset, err := f.Seek(0, io.SeekEnd)
+		require.NoError(t, err)
+
+		go func() {
+			time.Sleep(50 * time.Millisecond)
+			err := f.Truncate(0)
+			fmt.Println(err)
+		}()
+
+		event, err := blockUntilEvent(context.Background(), f, offset, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+		require.Equal(t, eventTruncated, event)
+	})
+}

internal/component/loki/source/file/internal/tail/file_test.go

@@ -238,8 +238,18 @@ func createFile(t *testing.T, name, content string) string {
 	return path
 }
 
-func recreateFile(t *testing.T, path, content string) {
-	require.NoError(t, os.WriteFile(path, []byte(content), 0600))
+func createEmptyFile(t *testing.T, name string) *os.File {
+	path := t.TempDir() + "/" + name
+	f, err := os.Create(path)
+	require.NoError(t, err)
+	return f
+}
+
+func createFileWithContent(t *testing.T, name, content string) *os.File {
+	path := createFile(t, name, content)
+	f, err := os.OpenFile(path, os.O_RDWR, 0)
+	require.NoError(t, err)
+	return f
 }
 
 func appendToFile(t *testing.T, name, content string) {