diff --git a/internal/2025/DayEleven/code_test.go b/internal/2025/DayEleven/code_test.go
new file mode 100644
index 0000000..0d44d95
--- /dev/null
+++ b/internal/2025/DayEleven/code_test.go
@@ -0,0 +1,24 @@
+package dayeleven
+
+import "testing"
+
+var testInput = []string{
+	"aaa: you hhh",
+	"you: bbb ccc",
+	"bbb: ddd eee",
+	"ccc: ddd eee fff",
+	"ddd: ggg",
+	"eee: out",
+	"fff: out",
+	"ggg: out",
+	"hhh: ccc fff iii",
+	"iii: out",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 5
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}