add tests for blockUntilExists

Author: kalleep

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

@@ -25,7 +25,6 @@ func blockUntilExists(ctx context.Context, cfg *Config) error {
 		} else if !os.IsNotExist(err) {
 			return err
 		}
-
 		backoff.Wait()
 	}
 

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

@@ -2,15 +2,51 @@ package tail
 
 import (
 	"context"
-	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
 )
 
+func TestBlockUntilExists(t *testing.T) {
+	watcherConfig := WatcherConfig{
+		MinPollFrequency: 5 * time.Millisecond,
+		MaxPollFrequency: 5 * time.Millisecond,
+	}
+
+	t.Run("should block until file exists", func(t *testing.T) {
+		filename := filepath.Join(t.TempDir(), "eventually")
+
+		go func() {
+			time.Sleep(10 * time.Millisecond)
+			createFileWithPath(t, filename, "")
+		}()
+
+		err := blockUntilExists(context.Background(), &Config{
+			Filename:      filename,
+			WatcherConfig: watcherConfig,
+		})
+		require.NoError(t, err)
+	})
+
+	t.Run("should exit when context is canceled", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		go func() {
+			time.Sleep(10 * time.Millisecond)
+			cancel()
+		}()
+
+		err := blockUntilExists(ctx, &Config{
+			Filename:      filepath.Join(t.TempDir(), "never"),
+			WatcherConfig: watcherConfig,
+		})
+		require.ErrorIs(t, err, context.Canceled)
+	})
+}
+
 func TestBlockUntilEvent(t *testing.T) {
 	watcherConfig := WatcherConfig{
 		MinPollFrequency: 5 * time.Millisecond,
@@ -22,7 +58,7 @@ func TestBlockUntilEvent(t *testing.T) {
 		defer f.Close()
 
 		go func() {
-			time.Sleep(50 * time.Millisecond)
+			time.Sleep(10 * time.Millisecond)
 			_, err := f.WriteString("updated")
 			require.NoError(t, err)
 		}()
@@ -40,7 +76,7 @@ func TestBlockUntilEvent(t *testing.T) {
 		defer f.Close()
 
 		go func() {
-			time.Sleep(50 * time.Millisecond)
+			time.Sleep(10 * time.Millisecond)
 			require.NoError(t, os.Chtimes(f.Name(), time.Now(), time.Now()))
 		}()
 
@@ -57,7 +93,7 @@ func TestBlockUntilEvent(t *testing.T) {
 		defer f.Close()
 
 		go func() {
-			time.Sleep(50 * time.Millisecond)
+			time.Sleep(10 * time.Millisecond)
 			removeFile(t, f.Name())
 		}()
 
@@ -91,9 +127,8 @@ func TestBlockUntilEvent(t *testing.T) {
 		require.NoError(t, err)
 
 		go func() {
-			time.Sleep(50 * time.Millisecond)
-			err := f.Truncate(0)
-			fmt.Println(err)
+			time.Sleep(10 * time.Millisecond)
+			require.NoError(t, f.Truncate(0))
 		}()
 
 		event, err := blockUntilEvent(context.Background(), f, offset, &Config{
@@ -103,4 +138,40 @@ func TestBlockUntilEvent(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, eventTruncated, event)
 	})
+
+	t.Run("should exit when context is canceled", func(t *testing.T) {
+		f := createEmptyFile(t, "startempty")
+		defer f.Close()
+
+		ctx, cancel := context.WithCancel(context.Background())
+		go func() {
+			time.Sleep(10 * time.Millisecond)
+			cancel()
+		}()
+
+		event, err := blockUntilEvent(ctx, f, 0, &Config{
+			Filename:      f.Name(),
+			WatcherConfig: watcherConfig,
+		})
+		require.ErrorIs(t, err, context.Canceled)
+		require.Equal(t, eventNone, event)
+	})
+}
+
+func createEmptyFile(t *testing.T, name string) *os.File {
+	path := filepath.Join(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 createFileWithPath(t *testing.T, path, content string) {
+	require.NoError(t, os.WriteFile(path, []byte(content), 0600))
 }

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

@@ -238,20 +238,6 @@ func createFile(t *testing.T, name, content string) string {
 	return path
 }
 
-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) {
 	f, err := os.OpenFile(name, os.O_APPEND|os.O_WRONLY, 0600)
 	require.NoError(t, err)