diff --git a/internal/2025/DayTwelve/code_test.go b/internal/2025/DayTwelve/code_test.go
new file mode 100644
index 0000000..df197cd
--- /dev/null
+++ b/internal/2025/DayTwelve/code_test.go
@@ -0,0 +1,47 @@
+package daytwelve
+
+import "testing"
+
+var testInput = []string{
+	"0:",
+	"###",
+	"##.",
+	"##.",
+	"",
+	"1:",
+	"###",
+	"##.",
+	".##",
+	"",
+	"2:",
+	".##",
+	"###",
+	"##.",
+	"",
+	"3:",
+	"##.",
+	"###",
+	"##.",
+	"",
+	"4:",
+	"###",
+	"#..",
+	"###",
+	"",
+	"5:",
+	"###",
+	".#.",
+	"###",
+	"",
+	"4x4: 0 0 0 0 2 0",
+	"12x5: 1 0 1 0 2 2",
+	"12x5: 1 0 1 0 3 2",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 2
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}