test(metrics): add regression test for invalid file path

Added TestZerologMetricsInvalidFileDoesNotPanic to ensure that if
the metrics log file cannot be opened, it gracefully degrades
instead of causing a nil pointer dereference.

Signed-off-by: abhaygoudannavar <abhaysgoudnvr@gmail.com>

Author: abhaygoudannavar

internal/metrics/metrics_test.go

@@ -20,6 +20,7 @@ import (
 	"testing"
 
 	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/require"
 )
 
 func TestZerologMetricsMetadata(t *testing.T) {
@@ -52,3 +53,18 @@ func TestZerologMetricsMetadata(t *testing.T) {
 		t.Errorf("timestampOrder = %v, want 0", got)
 	}
 }
+
+func TestZerologMetricsInvalidFileDoesNotPanic(t *testing.T) {
+	// Provide a path to a directory that definitely does not exist
+	invalidPath := "/does/not/exist/timestamps.log"
+	
+	// Create the metrics writer with timestamps enabled but an invalid path
+	writer := NewZerologMetrics(true, invalidPath, "container-test")
+	
+	// Before the fix, writer would be nil here.
+	require.NotNil(t, writer, "Expected NewZerologMetrics to return a fallback writer, got nil")
+
+	// This call would panic with a nil pointer dereference without the fix.
+	// With the fix, it will safely execute the mockWriter's no-op Capture().
+	writer.Capture(TS00)
+}