test: add p2 unit test

internal/2015/DayTwo/code_test.go

@@ -21,3 +21,23 @@ func TestPartOne(t *testing.T) {
 		})
 	}
 }
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"2x3x4", "2x3x4", 34},
+		{"1x1x10", "1x1x10", 14},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartTwo(%q) = %d, want %d", tt.input, got, tt.expected)
+			}
+		})
+	}
+}