diff --git a/libs/dnsx/day3_w09_wildcard_test.go b/libs/dnsx/day3_w09_wildcard_test.go
new file mode 100644
index 00000000..b0fb9a7a
--- /dev/null
+++ b/libs/dnsx/day3_w09_wildcard_test.go
@@ -0,0 +1,18 @@
+package dnsx
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOptionsWildcardFilteringValidation(t *testing.T) {
+	opts := DefaultOptions
+	opts.WildcardFilter = true
+	opts.WildcardThreshold = 5
+	opts.Domains = []string{"*.example.com", "api.example.com"}
+
+	assert.True(t, opts.WildcardFilter)
+	assert.Equal(t, 5, opts.WildcardThreshold)
+	assert.Equal(t, 2, len(opts.Domains))
+}