diff --git a/2017/18.cpp b/2017/18.cpp
index f1ef275..fa35066 100644
--- a/2017/18.cpp
+++ b/2017/18.cpp
@@ -238,7 +238,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto program = Parse(aocpp::Startup(argc, argv));
+  auto const program = Parse(*aocpp::Startup(argc, argv));
   std::cout << "Part 1: " << Part1(program) << std::endl;
   std::cout << "Part 2: " << Part2(program) << std::endl;
 }
diff --git a/2019/01.cpp b/2019/01.cpp
index a5c670a..75a33f8 100644
--- a/2019/01.cpp
+++ b/2019/01.cpp
@@ -45,7 +45,8 @@ TEST_CASE("part 2") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto& in = aocpp::Startup(argc, argv);
+  auto in_ptr = aocpp::Startup(argc, argv);
+  auto & in = *in_ptr;
 
   std::int64_t weight;
   std::int64_t part1 = 0;
diff --git a/2019/02.cpp b/2019/02.cpp
index 547e952..14770f6 100644
--- a/2019/02.cpp
+++ b/2019/02.cpp
@@ -37,7 +37,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
 
   std::cout << "Part 1: " << Compute(machine, 12, 2) << std::endl;
 
diff --git a/2019/03.cpp b/2019/03.cpp
index e899191..ae8ffe5 100644
--- a/2019/03.cpp
+++ b/2019/03.cpp
@@ -67,7 +67,8 @@ auto Record (
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto& in = aocpp::Startup(argc, argv);
+  auto in_ptr = aocpp::Startup(argc, argv);
+  auto & in = *in_ptr;
 
   std::string line;
   std::getline(in, line);
diff --git a/2019/04.cpp b/2019/04.cpp
index 9fd24fa..d6ade1a 100644
--- a/2019/04.cpp
+++ b/2019/04.cpp
@@ -44,7 +44,7 @@ auto Valid2(std::string const& str) {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto [lo,hi] = Parse(aocpp::Startup(argc, argv));
+  auto [lo,hi] = Parse(*aocpp::Startup(argc, argv));
 
   std::int64_t part1 = 0;
   std::int64_t part2 = 0;
diff --git a/2019/05.cpp b/2019/05.cpp
index 5dd5c59..62f9b40 100644
--- a/2019/05.cpp
+++ b/2019/05.cpp
@@ -18,7 +18,7 @@ auto Compute(Machine machine, ValueType d) -> ValueType {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   std::cout << "Part 1: " << Compute(machine, 1) << std::endl;
   std::cout << "Part 2: " << Compute(std::move(machine), 5) << std::endl;
 }
diff --git a/2019/06.cpp b/2019/06.cpp
index 5892116..0830e11 100644
--- a/2019/06.cpp
+++ b/2019/06.cpp
@@ -89,7 +89,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto parents = Parse(aocpp::Startup(argc, argv));
+  auto parents = Parse(*aocpp::Startup(argc, argv));
   std::cout << "Part 1: " << Part1(parents) << std::endl;
   std::cout << "Part 2: " << Part2(parents) << std::endl;
 }
diff --git a/2019/07.cpp b/2019/07.cpp
index 810805f..1b5182d 100644
--- a/2019/07.cpp
+++ b/2019/07.cpp
@@ -86,7 +86,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   std::cout << "Part 1: " << Part1(machine) << std::endl;
   std::cout << "Part 2: " << Part2(std::move(machine)) << std::endl;
 }
diff --git a/2019/08.cpp b/2019/08.cpp
index a479f3f..4a8974d 100644
--- a/2019/08.cpp
+++ b/2019/08.cpp
@@ -58,7 +58,7 @@ auto Draw(std::string const& picture) {
 
 auto main(int argc, char** argv) -> int {
   std::string line;
-  std::getline(aocpp::Startup(argc, argv), line);
+  std::getline(*aocpp::Startup(argc, argv), line);
   std::cout << "Part 1: " << Part1(line) << std::endl;
   Draw(Flatten(line));
 }
diff --git a/2019/09.cpp b/2019/09.cpp
index c25f2c7..96c7dcc 100644
--- a/2019/09.cpp
+++ b/2019/09.cpp
@@ -30,7 +30,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   std::cout << "Part 1: " << Compute(machine, 1) << std::endl;
   std::cout << "Part 2: " << Compute(std::move(machine), 2) << std::endl;
 }
diff --git a/2019/10.cpp b/2019/10.cpp
index 6e28f5a..0ca9e25 100644
--- a/2019/10.cpp
+++ b/2019/10.cpp
@@ -209,7 +209,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto grid = Grid::Parse(Startup(argc, argv));
+  auto grid = Grid::Parse(*Startup(argc, argv));
   auto [part1, base] = Part1(grid);
   std::cout << "Part 1: " << part1 << std::endl;
   std::cout << "Part 2: " << Part2(grid, base, 200) << std::endl;
diff --git a/2019/11.cpp b/2019/11.cpp
index 66aefb2..5b8740b 100644
--- a/2019/11.cpp
+++ b/2019/11.cpp
@@ -38,7 +38,7 @@ auto Compute(Machine machine, ValueType start)
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   std::cout << "Part 1: " << Compute(machine, 0).size() << "\nPart 2\n";
   Draw(std::cout, Compute(std::move(machine), 1));
 }
diff --git a/2019/12.cpp b/2019/12.cpp
index fc092eb..685c832 100644
--- a/2019/12.cpp
+++ b/2019/12.cpp
@@ -94,7 +94,7 @@ auto Part2(std::array<std::vector<Particle>, 3> const& ps) {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto ps = Parse(aocpp::Startup(argc, argv));
+  auto ps = Parse(*aocpp::Startup(argc, argv));
   auto part2 = Part2(ps);
   auto part1 = Part1(std::move(ps), 1000);
 
diff --git a/2019/13.cpp b/2019/13.cpp
index 0bd3048..2a3a5b9 100644
--- a/2019/13.cpp
+++ b/2019/13.cpp
@@ -60,7 +60,7 @@ auto Compute2(Machine machine) {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   std::cout << "Part 1: " << Compute1(machine) << std::endl;
   std::cout << "Part 2: " << Compute2(std::move(machine)) << std::endl;
 }
diff --git a/2019/14.cpp b/2019/14.cpp
index 760eb7a..ac450f0 100644
--- a/2019/14.cpp
+++ b/2019/14.cpp
@@ -229,7 +229,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto recipes = Parse(aocpp::Startup(argc, argv));
+  auto recipes = Parse(*aocpp::Startup(argc, argv));
   auto machine = Machine(recipes);
   auto part1 = machine(1);
   auto part2 = ComputeFuel(machine, 1'000'000'000'000);
diff --git a/2019/15.cpp b/2019/15.cpp
index d6cab80..96b541b 100644
--- a/2019/15.cpp
+++ b/2019/15.cpp
@@ -91,7 +91,7 @@ auto Compute(std::map<Coord, ValueType> world) -> std::pair<int, int> {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto [p1,p2] = Compute(Explore(Machine{ParseStream(aocpp::Startup(argc, argv))}));
+  auto [p1,p2] = Compute(Explore(Machine{ParseStream(*aocpp::Startup(argc, argv))}));
   std::cout << "Part 1: " << p1 << std::endl;
   std::cout << "Part 2: " << p2 << std::endl;
 }
diff --git a/2019/16.cpp b/2019/16.cpp
index ceaa856..61e3c6a 100644
--- a/2019/16.cpp
+++ b/2019/16.cpp
@@ -119,7 +119,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto input = Parse(aocpp::Startup(argc, argv));
+  auto input = Parse(*aocpp::Startup(argc, argv));
 
   std::cout << "Part 1: " << Compute(input, 100, 0) << std::endl;
   std::cout << "Part 2: " << Part2(input) << std::endl;
diff --git a/2019/17.cpp b/2019/17.cpp
index aedf05f..d29e0e9 100644
--- a/2019/17.cpp
+++ b/2019/17.cpp
@@ -214,7 +214,7 @@ auto GatherScore(Machine m, std::string const& program) -> ValueType {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto machine = Machine{ParseStream(aocpp::Startup(argc, argv))};
+  auto machine = Machine{ParseStream(*aocpp::Startup(argc, argv))};
   auto grid = GatherOutput(machine);
   auto part1 = ScaffoldAlignments(grid);
   auto path = ComputePath(grid);
diff --git a/2019/18.cpp b/2019/18.cpp
index b0ce910..b11ea30 100644
--- a/2019/18.cpp
+++ b/2019/18.cpp
@@ -160,7 +160,7 @@ auto Part2(Grid & grid, Features & features) {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto grid = Grid::Parse(Startup(argc, argv));
+  auto grid = Grid::Parse(*Startup(argc, argv));
   auto features = FindFeatures(grid);
   auto distances = FindDistances(grid, features);
   std::cout << "Part 1: " << SolveMaze(distances, "@") << std::endl;
diff --git a/2019/19.cpp b/2019/19.cpp
index 63abf22..b5e8f0f 100644
--- a/2019/19.cpp
+++ b/2019/19.cpp
@@ -46,7 +46,7 @@ auto Part2(Scanner const& scanner) {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto scanner = Scanner{Machine{ParseStream(aocpp::Startup(argc, argv))}};
+  auto scanner = Scanner{Machine{ParseStream(*aocpp::Startup(argc, argv))}};
   std::cout << "Part 1: " << Part1(scanner) << std::endl;
   std::cout << "Part 2: " << Part2(scanner) << std::endl;
 }
diff --git a/2019/20.cpp b/2019/20.cpp
index 773d62e..54d6d09 100644
--- a/2019/20.cpp
+++ b/2019/20.cpp
@@ -150,7 +150,7 @@ auto SolveMaze(Distances const& distances, bool const recursive) -> std::int64_t
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto map = Grid::Parse(Startup(argc, argv));
+  auto map = Grid::Parse(*Startup(argc, argv));
   auto portals = FindPortals(map);
   auto distances = FindDistances(map, portals);
 
diff --git a/2019/21.cpp b/2019/21.cpp
index 95c1e0a..af00136 100644
--- a/2019/21.cpp
+++ b/2019/21.cpp
@@ -263,7 +263,7 @@ auto Compute(
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  Machine machine {ParseStream(aocpp::Startup(argc, argv))};
+  Machine machine {ParseStream(*aocpp::Startup(argc, argv))};
 
   Compute(machine, 4,
   { "#####.###########",
diff --git a/2019/22.cpp b/2019/22.cpp
index de4f07a..f0a1f94 100644
--- a/2019/22.cpp
+++ b/2019/22.cpp
@@ -115,7 +115,7 @@ auto Many(Shuffle<Cards> shuffle, unsigned long n) -> Shuffle<Cards> {
 } // namespace
 
 auto main(int argc, char** argv) -> int {
-  auto instructions = Parse(Startup(argc, argv));
+  auto instructions = Parse(*Startup(argc, argv));
 
   auto shuffle1 = FollowInstructions<10007>(instructions);
   std::cout << "Part 1: " << shuffle1(2019) << std::endl;
diff --git a/2019/23.cpp b/2019/23.cpp
index 3f378dd..e4e272d 100644
--- a/2019/23.cpp
+++ b/2019/23.cpp
@@ -56,7 +56,7 @@ auto Interact(Ethernet & ethernet, Machine & m, std::optional<Payload> p) -> voi
 } // namespace
 
 auto main(int const argc, char** const argv) -> int {
-  auto machines = BuildNetwork(Machine{ParseStream(aocpp::Startup(argc, argv))});
+  auto machines = BuildNetwork(Machine{ParseStream(*aocpp::Startup(argc, argv))});
   auto ethernet = Ethernet{};
 
   std::optional<ValueType> part1;
diff --git a/2019/24.cpp b/2019/24.cpp
index 2640b7d..72e6620 100644
--- a/2019/24.cpp
+++ b/2019/24.cpp
@@ -84,8 +84,8 @@ auto Step(std::vector<C> const& bugs, F with_neighbors = F{})
     case 2:
       if (!std::binary_search(bugs.begin(), bugs.end(), k)) {
         result.push_back(k);
-        break;
       }
+      break;
     }
   }
 
@@ -136,7 +136,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto const bugs = FindBugs(Grid::Parse(Startup(argc, argv)));
+  auto const bugs = FindBugs(Grid::Parse(*Startup(argc, argv)));
   std::cout << "Part 1: " << Part1(bugs) << std::endl;
   std::cout << "Part 2: " << Part2(std::move(bugs), 200) << std::endl;
 }
diff --git a/2019/25.cpp b/2019/25.cpp
index f75d163..e18cacd 100644
--- a/2019/25.cpp
+++ b/2019/25.cpp
@@ -76,5 +76,5 @@ auto main(int argc, char** argv) -> int {
 
   Search(script);
 
-  RunWithIO(Machine{ParseStream(aocpp::Startup(argc, argv))}, script);
+  RunWithIO(Machine{ParseStream(*aocpp::Startup(argc, argv))}, script);
 }
diff --git a/2020/02.cpp b/2020/02.cpp
index a2d5c75..d25aa90 100644
--- a/2020/02.cpp
+++ b/2020/02.cpp
@@ -57,7 +57,9 @@ TEST_CASE("part 2") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto & in = aocpp::Startup(argc, argv);
+  auto const in_ptr = aocpp::Startup(argc, argv);
+  auto & in = *in_ptr;
+
   std::uint64_t part1{}, part2{};
   
   std::string line;
diff --git a/2020/03.cpp b/2020/03.cpp
index d283873..a06e007 100644
--- a/2020/03.cpp
+++ b/2020/03.cpp
@@ -76,7 +76,7 @@ TEST_CASE("part 2") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto grid = Grid::Parse(Startup(argc, argv));
+  auto grid = Grid::Parse(*Startup(argc, argv));
   std::cout << "Part 1: " << Part1(grid) << std::endl;
   std::cout << "Part 2: " << Part2(grid) << std::endl;
 }
diff --git a/2020/10.cpp b/2020/10.cpp
index 813b70c..05e85f7 100644
--- a/2020/10.cpp
+++ b/2020/10.cpp
@@ -76,7 +76,7 @@ TEST_CASE("part 2") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto adapters = Parse(aocpp::Startup(argc, argv));
+  auto adapters = Parse(*aocpp::Startup(argc, argv));
   std::cout << "Part 1: " << Part1(adapters) << std::endl;
   std::cout << "Part 2: " << Part2(adapters) << std::endl;
 }
diff --git a/2020/16.cpp b/2020/16.cpp
index 3ce075f..7839184 100644
--- a/2020/16.cpp
+++ b/2020/16.cpp
@@ -185,7 +185,7 @@ TEST_SUITE("documented examples") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto input = Parse(aocpp::Startup(argc, argv));
+  auto input = Parse(*aocpp::Startup(argc, argv));
   std::cout << "Part 1: " << Part1(input) << std::endl;
   std::cout << "Part 2: " << Part2(input) << std::endl;
 }
diff --git a/2020/18.cpp b/2020/18.cpp
index 804e06a..98b94f2 100644
--- a/2020/18.cpp
+++ b/2020/18.cpp
@@ -141,7 +141,8 @@ TEST_CASE("errors") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto & in = aocpp::Startup(argc, argv);
+  auto const in_ptr = aocpp::Startup(argc, argv);
+  auto & in = *in_ptr;
 
   std::int64_t part1 = 0;
   std::int64_t part2 = 0;
diff --git a/2020/21.cpp b/2020/21.cpp
index 0dd56e6..79edc15 100644
--- a/2020/21.cpp
+++ b/2020/21.cpp
@@ -179,7 +179,7 @@ TEST_CASE("part 2") {
 }
 
 auto main(int argc, char** argv) -> int {
-  auto input = Parse(Startup(argc, argv));
+  auto const input = Parse(*Startup(argc, argv));
   std::cout << "Part 1: " << Part1(input) << std::endl;
   std::cout << "Part 2: " << Part2(input) << std::endl;
 }
diff --git a/lib/include/aocpp/Startup.hpp b/lib/include/aocpp/Startup.hpp
index 3b007d8..01c612f 100644
--- a/lib/include/aocpp/Startup.hpp
+++ b/lib/include/aocpp/Startup.hpp
@@ -3,11 +3,23 @@
 
 #include <fstream>
 #include <iostream>
+#include <memory>
 #include <optional>
 
 namespace aocpp {
 
-auto Startup(int argc, char ** argv) -> std::istream&;
+class ConditionalDeleter {
+  bool should_delete_;
+
+public:
+  ConditionalDeleter(bool should_delete) : should_delete_ {should_delete} {}
+  
+  template <typename T>
+  auto operator()(T * pointer) -> void { if (should_delete_) { delete pointer; }}
+};
+
+auto Startup(int argc, char ** argv) -> std::unique_ptr<std::istream, ConditionalDeleter>;
+
 }
 
 #endif
diff --git a/lib/src/Startup.cpp b/lib/src/Startup.cpp
index b8f725f..8b63eea 100644
--- a/lib/src/Startup.cpp
+++ b/lib/src/Startup.cpp
@@ -12,19 +12,25 @@
 
 namespace aocpp {
 
-auto Startup(int argc, char ** argv) -> std::istream& {
-  if (std::getenv("DOCTEST")) {
-    exit(doctest::Context{argc, argv}.run());
-  }
+auto Startup(int argc, char ** argv) -> std::unique_ptr<std::istream, ConditionalDeleter> {
+  bool should_delete;
+  std::istream* result_ptr;
 
-  static std::ifstream fin;
   switch (argc) {
-  case 2: fin = std::ifstream{argv[1]}; return fin;
-  case 1: return std::cin;
-  default:
-    std::cerr << "bad arguments\n";
-    exit(EXIT_FAILURE);
+    case 2:
+      should_delete = true;
+      result_ptr = new std::ifstream{argv[1]};
+      break;
+    case 1:
+      should_delete = false;
+      result_ptr = &std::cin;
+      break;
+    default:
+      std::cerr << "bad arguments\n";
+      exit(EXIT_FAILURE);
   }
+
+  return {result_ptr, should_delete};
 }
 
 }