diff --git a/test/e2e/CMakeLists.txt b/test/e2e/CMakeLists.txt
index 5fc3bd09..52b059f1 100644
--- a/test/e2e/CMakeLists.txt
+++ b/test/e2e/CMakeLists.txt
@@ -4,6 +4,8 @@ target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::core::json
 target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::jsonbinpack::compiler)
 target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::jsonbinpack::runtime)
 target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::core::jsonschema)
+target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::core::io)
+target_link_libraries(jsonbinpack_e2e_test_runner PRIVATE sourcemeta::core::options)
 set_target_properties(jsonbinpack_e2e_test_runner
   PROPERTIES FOLDER "JSON BinPack/E2E")
 
diff --git a/test/e2e/runner.cc b/test/e2e/runner.cc
index 3bb45cfc..28a31f7e 100644
--- a/test/e2e/runner.cc
+++ b/test/e2e/runner.cc
@@ -1,31 +1,152 @@
 #include <sourcemeta/jsonbinpack/compiler.h>
 #include <sourcemeta/jsonbinpack/runtime.h>
 
+#include <sourcemeta/core/io.h>
 #include <sourcemeta/core/json.h>
 #include <sourcemeta/core/jsonschema.h>
+#include <sourcemeta/core/options.h>
 
-#include <cassert>    // assert
-#include <cstdlib>    // EXIT_SUCCESS, EXIT_FAILURE
-#include <filesystem> // std::filesystem
-#include <fstream>    // std::ifstream, std::ofstream
-#include <ios>        // std::ios_base, std::ios::binary
-#include <iostream>   // std::cerr
-#include <string>     // std::to_string
+#include <algorithm>    // std::min
+#include <cassert>      // assert
+#include <charconv>     // std::from_chars
+#include <cstdint>      // std::int64_t
+#include <cstdlib>      // EXIT_SUCCESS, EXIT_FAILURE
+#include <filesystem>   // std::filesystem
+#include <iostream>     // std::cerr
+#include <optional>     // std::optional, std::nullopt
+#include <sstream>      // std::istringstream, std::ostringstream
+#include <string>       // std::string, std::to_string
+#include <string_view>  // std::string_view
+#include <system_error> // std::errc
 
 constexpr auto DEFAULT_METASCHEMA =
     "https://json-schema.org/draft/2020-12/schema";
 
+namespace {
+
+auto prettify_to_string(const sourcemeta::core::JSON &document) -> std::string {
+  std::ostringstream stream;
+  sourcemeta::core::prettify(document, stream);
+  stream << "\n";
+  return stream.str();
+}
+
+auto report_missing_artifact(const std::filesystem::path &path) -> void {
+  std::cerr << "The artifact does not exist: " << path.string() << "\n";
+}
+
+auto report_artifact_mismatch(const std::filesystem::path &path) -> void {
+  std::cerr << "The artifact does not match: " << path.string() << "\n";
+}
+
+auto first_difference(const std::string_view left, const std::string_view right)
+    -> std::string_view::size_type {
+  const auto bound{std::min(left.size(), right.size())};
+  for (std::string_view::size_type index{0}; index < bound; index++) {
+    if (left[index] != right[index]) {
+      return index;
+    }
+  }
+
+  return bound;
+}
+
+auto check_text_artifact(const std::filesystem::path &path,
+                         const std::string_view actual) -> bool {
+  if (!std::filesystem::is_regular_file(path)) {
+    report_missing_artifact(path);
+    return false;
+  }
+
+  const auto expected{sourcemeta::core::read_file_to_string(path)};
+  if (expected == actual) {
+    return true;
+  }
+
+  report_artifact_mismatch(path);
+  std::cerr << "GOT:\n" << actual << "EXPECTED:\n" << expected;
+  return false;
+}
+
+auto check_binary_artifact(const std::filesystem::path &path,
+                           const std::string_view actual) -> bool {
+  if (!std::filesystem::is_regular_file(path)) {
+    report_missing_artifact(path);
+    return false;
+  }
+
+  const auto expected{sourcemeta::core::read_file_to_string(path)};
+  if (expected == actual) {
+    return true;
+  }
+
+  report_artifact_mismatch(path);
+  std::cerr << "GOT: " << actual.size() << " bytes\n"
+            << "EXPECTED: " << expected.size() << " bytes\n"
+            << "FIRST DIFFERENCE AT BYTE: "
+            << first_difference(actual, expected) << "\n";
+  return false;
+}
+
+auto parse_size_artifact(const std::string_view contents)
+    -> std::optional<std::string::size_type> {
+  std::string::size_type result{0};
+  const auto *const end{contents.data() + contents.size()};
+  const auto outcome{std::from_chars(contents.data(), end, result)};
+  if (outcome.ec != std::errc{} || std::string_view{outcome.ptr, end} != "\n") {
+    return std::nullopt;
+  }
+
+  return result;
+}
+
+auto check_size_artifact(const std::filesystem::path &path,
+                         const std::string::size_type actual) -> bool {
+  if (!std::filesystem::is_regular_file(path)) {
+    report_missing_artifact(path);
+    return false;
+  }
+
+  const auto contents{std::to_string(actual) + "\n"};
+  const auto expected{sourcemeta::core::read_file_to_string(path)};
+  if (expected == contents) {
+    return true;
+  }
+
+  report_artifact_mismatch(path);
+  const auto previous{parse_size_artifact(expected)};
+  if (previous.has_value()) {
+    const auto difference{static_cast<std::int64_t>(actual) -
+                          static_cast<std::int64_t>(previous.value())};
+    std::cerr << "GOT: " << actual << " bytes\n"
+              << "EXPECTED: " << previous.value() << " bytes\n"
+              << "DIFFERENCE: " << (difference > 0 ? "+" : "") << difference
+              << " bytes\n";
+  } else {
+    std::cerr << "GOT:\n" << contents << "EXPECTED:\n" << expected;
+  }
+
+  return false;
+}
+
+} // namespace
+
 auto main(int argc, char *argv[]) -> int {
-  if (argc <= 2) {
-    std::cerr << "Usage: " << argv[0] << " <instance.json> <directory>\n";
+  sourcemeta::core::Options application;
+  application.flag("write", {"w"});
+  application.parse(argc, argv);
+
+  if (application.positional().size() < 2) {
+    std::cerr << "Usage: " << argv[0]
+              << " <instance.json> <directory> [--write]\n";
     return EXIT_FAILURE;
   }
 
-  const std::filesystem::path instance_path{argv[1]};
+  const std::filesystem::path instance_path{application.positional().at(0)};
   assert(std::filesystem::is_regular_file(instance_path));
   const sourcemeta::core::JSON instance =
       sourcemeta::core::read_json(instance_path);
-  const std::filesystem::path directory{argv[2]};
+  const std::filesystem::path directory{application.positional().at(1)};
   assert(std::filesystem::is_directory(directory));
 
   // Schema
@@ -38,59 +159,34 @@ auto main(int argc, char *argv[]) -> int {
                                         sourcemeta::core::schema_resolver,
                                         DEFAULT_METASCHEMA);
 
-  std::ofstream canonical_output_stream(directory / "canonical.json",
-                                        std::ios::binary);
-  canonical_output_stream.exceptions(std::ios_base::badbit);
-
   const sourcemeta::core::SchemaFrame frame{
       sourcemeta::core::SchemaFrame::Mode::Locations, schema,
       sourcemeta::core::schema_walker, sourcemeta::core::schema_resolver,
       DEFAULT_METASCHEMA};
   sourcemeta::core::schema_format(schema, frame);
-  sourcemeta::core::prettify(schema, canonical_output_stream);
-  canonical_output_stream << "\n";
-  canonical_output_stream.flush();
-  canonical_output_stream.close();
+  const auto canonical{prettify_to_string(schema)};
 
   // Compile
   sourcemeta::jsonbinpack::compile(schema, sourcemeta::core::schema_walker,
                                    sourcemeta::core::schema_resolver,
                                    DEFAULT_METASCHEMA);
 
-  std::ofstream encoding_output_stream(directory / "encoding.json",
-                                       std::ios::binary);
-  encoding_output_stream.exceptions(std::ios_base::badbit);
-  sourcemeta::core::prettify(schema, encoding_output_stream);
-  encoding_output_stream << "\n";
-  encoding_output_stream.flush();
-  encoding_output_stream.close();
+  const auto encoding_document{prettify_to_string(schema)};
 
   // Encoder
   const sourcemeta::jsonbinpack::Encoding encoding{
       sourcemeta::jsonbinpack::load(schema)};
-  std::ofstream output_stream(directory / "output.bin", std::ios::binary);
-  output_stream.exceptions(std::ios_base::badbit);
+  std::ostringstream output_stream;
   sourcemeta::jsonbinpack::Encoder encoder{output_stream};
   encoder.write(instance, encoding);
-  output_stream.flush();
-  const auto size{output_stream.tellp()};
-  output_stream.close();
-  std::ofstream size_stream(directory / "size.txt", std::ios::binary);
-  size_stream.exceptions(std::ios_base::badbit);
-  size_stream << std::to_string(size) << "\n";
-  size_stream.flush();
-  size_stream.close();
+  const auto output{output_stream.str()};
 
   // Decoder
-  std::ifstream data_stream{directory / "output.bin", std::ios::binary};
-  data_stream.exceptions(std::ios_base::badbit);
+  std::istringstream data_stream{output};
   sourcemeta::jsonbinpack::Decoder decoder{data_stream};
   const sourcemeta::core::JSON result = decoder.read(encoding);
 
-  // Report results
-  if (result == instance) {
-    return EXIT_SUCCESS;
-  } else {
+  if (result != instance) {
     std::cerr << "GOT:\n";
     sourcemeta::core::prettify(result, std::cerr);
     std::cerr << "\nEXPECTED:\n";
@@ -98,4 +194,33 @@ auto main(int argc, char *argv[]) -> int {
     std::cerr << "\n";
     return EXIT_FAILURE;
   }
+
+  const std::filesystem::path canonical_path{directory / "canonical.json"};
+  const std::filesystem::path encoding_path{directory / "encoding.json"};
+  const std::filesystem::path output_path{directory / "output.bin"};
+  const std::filesystem::path size_path{directory / "size.txt"};
+
+  if (application.contains("write")) {
+    sourcemeta::core::write_file(canonical_path, canonical);
+    sourcemeta::core::write_file(encoding_path, encoding_document);
+    sourcemeta::core::write_file(output_path, output);
+    sourcemeta::core::write_file(size_path,
+                                 std::to_string(output.size()) + "\n");
+    return EXIT_SUCCESS;
+  }
+
+  auto matches{check_text_artifact(canonical_path, canonical)};
+  matches = check_text_artifact(encoding_path, encoding_document) && matches;
+  matches = check_binary_artifact(output_path, output) && matches;
+  matches = check_size_artifact(size_path, output.size()) && matches;
+
+  if (!matches) {
+    std::cerr << "\nIf these changes are expected, re-run as follows to "
+                 "update the artifacts:\n  "
+              << argv[0] << " " << instance_path.string() << " "
+              << directory.string() << " --write\n";
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
 }