test: add unit test for part one

internal/2016/DayTwo/code_test.go

@@ -0,0 +1,15 @@
+package daytwo
+
+import (
+	"testing"
+)
+
+var testInput = []string{"ULL", "RRDDD", "LURDL", "UUUUD"}
+
+func TestPartOne(t *testing.T) {
+	expected := 1985
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}