diff --git a/internal/2025/DayOne/code_test.go b/internal/2025/DayOne/code_test.go
new file mode 100644
index 0000000..15b0715
--- /dev/null
+++ b/internal/2025/DayOne/code_test.go
@@ -0,0 +1,24 @@
+package dayone
+
+import "testing"
+
+var testInput = []string{
+	"L68",
+	"L30",
+	"R48",
+	"L5",
+	"R60",
+	"L55",
+	"L1",
+	"L99",
+	"R14",
+	"L82",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 3
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}