Various improvements.

serial/serial_test.go

@@ -2,6 +2,7 @@ package serial_test
 
 import (
 	"errors"
+	"fmt"
 	"testing"
 	"testing/quick"
 
@@ -243,7 +244,30 @@ func TestRandomCodeFailsWhenAllIndicesInUse(t *testing.T) {
 	_, _, err := serial.RandomCode(func(candidate uint32) bool {
 		return true
 	})
-	if !errors.Is(err, serial.ErrRandomGenerationFailed) {
-		t.Fatalf("expected random generation failed error, got: %v", err)
+	if !errors.Is(err, serial.ErrNoAvailableIndex) {
+		t.Fatalf("expected no available index error, got: %v", err)
+	}
+}
+
+func TestRandomCodeWithOptionsMaxAttempts(t *testing.T) {
+	_, _, err := serial.RandomCodeWithOptions(serial.RandomCodeOptions{
+		MaxAttempts: 1,
+		IsInUse: func(candidate uint32) bool {
+			return true
+		},
+	})
+	if !errors.Is(err, serial.ErrNoAvailableIndex) {
+		t.Fatalf("expected no available index error, got: %v", err)
+	}
+}
+
+func TestRandomCodeWithOptionsRandomSourceFailure(t *testing.T) {
+	_, _, err := serial.RandomCodeWithOptions(serial.RandomCodeOptions{
+		RandomIndex: func(max uint32) (uint32, error) {
+			return 0, fmt.Errorf("rng down")
+		},
+	})
+	if !errors.Is(err, serial.ErrRandomSourceFailed) {
+		t.Fatalf("expected random source failed error, got: %v", err)
 	}
 }