diff --git a/include/substrait/common/Io.h b/include/substrait/common/Io.h
index a2c18726..a53697d8 100644
--- a/include/substrait/common/Io.h
+++ b/include/substrait/common/Io.h
@@ -20,7 +20,7 @@ enum class PlanFileFormat {
 };
 
 /*
- * \\brief Loads a Substrait plan of any format from the given file.
+ * \brief Loads a Substrait plan of any format from the given file.
  *
  * loadPlan determines which file type the specified file is and then calls
  * the appropriate load/parse method to consume it preserving any error
@@ -29,8 +29,8 @@ enum class PlanFileFormat {
  * This will load the plan into memory and then convert it consuming twice the
  * amount of memory that it consumed on disk.
  *
- * \\param input_filename The filename containing the plan to convert.
- * \\return If loading was successful, returns a plan.  If loading was not
+ * \param input_filename The filename containing the plan to convert.
+ * \return If loading was successful, returns a plan.  If loading was not
  * successful this is a status containing a list of parse errors in the status's
  * message.
  */
@@ -38,7 +38,7 @@ absl::StatusOr<::substrait::proto::Plan> loadPlan(
     std::string_view input_filename);
 
 /*
- * \\brief Writes the provided plan to disk.
+ * \brief Writes the provided plan to disk.
  *
  * savePlan writes the provided plan in the specified format to the specified
  * location.
@@ -47,10 +47,10 @@ absl::StatusOr<::substrait::proto::Plan> loadPlan(
  * format as the original plan as well as the annotated parse tree will need to
  * reside in memory during the process.
  *
- * \\param plan
- * \\param output_filename
- * \\param format
- * \\return
+ * \param plan
+ * \param output_filename
+ * \param format
+ * \return
  */
 absl::Status savePlan(
     const ::substrait::proto::Plan& plan,
diff --git a/src/substrait/common/Io.cpp b/src/substrait/common/Io.cpp
index 4c5b1c24..af06066c 100644
--- a/src/substrait/common/Io.cpp
+++ b/src/substrait/common/Io.cpp
@@ -55,7 +55,6 @@ absl::StatusOr<::substrait::proto::Plan> loadPlan(
     case PlanFileFormat::kText:
       return textplan::loadFromText(*contentOrError);
   }
-  return absl::UnimplementedError("Unexpected encoding requested.");
 }
 
 absl::Status savePlan(
diff --git a/src/substrait/common/tests/IoTest.cpp b/src/substrait/common/tests/IoTest.cpp
index bf8dd00d..09a7283e 100644
--- a/src/substrait/common/tests/IoTest.cpp
+++ b/src/substrait/common/tests/IoTest.cpp
@@ -2,6 +2,8 @@
 
 #include "substrait/common/Io.h"
 
+#include <filesystem>
+
 #include <gmock/gmock-matchers.h>
 #include <gtest/gtest.h>
 #include <protobuf-matchers/protocol-buffer-matchers.h>
@@ -42,23 +44,33 @@ TEST_F(IoTest, LoadMissingFile) {
 
 class SaveAndLoadTestFixture : public ::testing::TestWithParam<PlanFileFormat> {
  public:
-  ~SaveAndLoadTestFixture() override {
-    for (const auto& filename : testFiles_) {
-      unlink(filename.c_str());
+  void SetUp() override {
+    testFileDirectory_ = std::filesystem::temp_directory_path() /
+        std::filesystem::path("my_temp_dir");
+
+    if (!std::filesystem::create_directory(testFileDirectory_)) {
+      std::cerr << "Failed to create temporary directory." << std::endl;
+      testFileDirectory_.clear();
+    }
+  }
+
+  void TearDown() override {
+    if (!testFileDirectory_.empty()) {
+      std::filesystem::remove_all(testFileDirectory_);
     }
   }
 
-  void registerCleanup(const char* filename) {
-    testFiles_.emplace_back(filename);
+  static std::string makeTempFileName() {
+    static int tempFileNum = 0;
+    return "testfile" + std::to_string(++tempFileNum);
   }
 
- private:
-  std::vector<std::string> testFiles_;
+ protected:
+  std::string testFileDirectory_;
 };
 
 TEST_P(SaveAndLoadTestFixture, SaveAndLoad) {
-  auto tempFilename = std::tmpnam(nullptr);
-  registerCleanup(tempFilename);
+  auto tempFilename = testFileDirectory_ + "/" + makeTempFileName();
   PlanFileFormat encoding = GetParam();
 
   ::substrait::proto::Plan plan;
diff --git a/src/substrait/textplan/CMakeLists.txt b/src/substrait/textplan/CMakeLists.txt
index 1e8b7dbb..eda37d58 100644
--- a/src/substrait/textplan/CMakeLists.txt
+++ b/src/substrait/textplan/CMakeLists.txt
@@ -20,10 +20,10 @@ add_library(error_listener SubstraitErrorListener.cpp SubstraitErrorListener.h)
 
 add_library(parse_result ParseResult.cpp ParseResult.h)
 
-add_dependencies(symbol_table substrait_proto substrait_common
+add_dependencies(symbol_table substrait_proto substrait_common absl::strings
                  fmt::fmt-header-only)
 
-target_link_libraries(symbol_table fmt::fmt-header-only
+target_link_libraries(symbol_table fmt::fmt-header-only absl::strings
                       substrait_textplan_converter)
 
 # Provide access to the generated protobuffer headers hierarchy.
diff --git a/src/substrait/textplan/StringManipulation.cpp b/src/substrait/textplan/StringManipulation.cpp
index ce37c9bb..cb11e53a 100644
--- a/src/substrait/textplan/StringManipulation.cpp
+++ b/src/substrait/textplan/StringManipulation.cpp
@@ -19,16 +19,4 @@ bool endsWith(std::string_view haystack, std::string_view needle) {
       haystack.substr(haystack.size() - needle.size(), needle.size()) == needle;
 }
 
-std::string joinLines(
-    std::vector<std::string> lines,
-    std::string_view separator) {
-  auto concatWithSeparator = [separator](std::string a, const std::string& b) {
-    return std::move(a) + std::string(separator) + b;
-  };
-
-  auto result = std::accumulate(
-      std::next(lines.begin()), lines.end(), lines[0], concatWithSeparator);
-  return result;
-}
-
 } // namespace io::substrait::textplan
diff --git a/src/substrait/textplan/StringManipulation.h b/src/substrait/textplan/StringManipulation.h
index d0d602e6..8edf7ea5 100644
--- a/src/substrait/textplan/StringManipulation.h
+++ b/src/substrait/textplan/StringManipulation.h
@@ -14,9 +14,4 @@ bool startsWith(std::string_view haystack, std::string_view needle);
 // Returns true if the string 'haystack' ends with the string 'needle'.
 bool endsWith(std::string_view haystack, std::string_view needle);
 
-// Joins a vector of strings into a single string separated by separator.
-std::string joinLines(
-    std::vector<std::string> lines,
-    std::string_view separator = "\n");
-
 } // namespace io::substrait::textplan
diff --git a/src/substrait/textplan/converter/LoadBinary.cpp b/src/substrait/textplan/converter/LoadBinary.cpp
index 65e5694c..c5d9f4ce 100644
--- a/src/substrait/textplan/converter/LoadBinary.cpp
+++ b/src/substrait/textplan/converter/LoadBinary.cpp
@@ -2,6 +2,7 @@
 
 #include "substrait/textplan/converter/LoadBinary.h"
 
+#include <absl/strings/str_join.h>
 #include <fmt/format.h>
 #include <google/protobuf/io/tokenizer.h>
 #include <google/protobuf/text_format.h>
@@ -83,7 +84,7 @@ absl::StatusOr<::substrait::proto::Plan> loadFromProtoText(
   parser.RecordErrorsTo(&collector);
   if (!parser.ParseFromString(text, &plan)) {
     auto errors = collector.getErrors();
-    return absl::InternalError(joinLines(errors));
+    return absl::InternalError(absl::StrJoin(errors, ""));
   }
   return plan;
 }
diff --git a/src/substrait/textplan/converter/SaveBinary.cpp b/src/substrait/textplan/converter/SaveBinary.cpp
index e7347269..c8dd6c07 100644
--- a/src/substrait/textplan/converter/SaveBinary.cpp
+++ b/src/substrait/textplan/converter/SaveBinary.cpp
@@ -2,6 +2,7 @@
 
 #include "substrait/textplan/converter/SaveBinary.h"
 
+#include <absl/strings/str_join.h>
 #include <fmt/format.h>
 #include <google/protobuf/io/zero_copy_stream_impl.h>
 #include <google/protobuf/text_format.h>
@@ -34,8 +35,10 @@ absl::Status savePlanToBinary(
     return ::absl::UnknownError("Failed to write plan to stream.");
   }
 
+  if (!stream->Close()) {
+    return absl::AbortedError("Failed to close file descriptor.");
+  }
   delete stream;
-  close(outputFileDescriptor);
   return absl::OkStatus();
 }
 
@@ -54,11 +57,10 @@ absl::Status savePlanToJson(
     return absl::UnknownError("Failed to save plan as a JSON protobuf.");
   }
   stream << output;
+  stream.close();
   if (stream.fail()) {
     return absl::UnknownError("Failed to write the plan as a JSON protobuf.");
   }
-
-  stream.close();
   return absl::OkStatus();
 }
 
@@ -74,13 +76,13 @@ absl::Status savePlanToText(
   auto result = parseBinaryPlan(plan);
   auto errors = result.getAllErrors();
   if (!errors.empty()) {
-    return absl::UnknownError(joinLines(errors));
+    return absl::UnknownError(absl::StrJoin(errors, ""));
   }
   stream << SymbolTablePrinter::outputToText(result.getSymbolTable());
+  stream.close();
   if (stream.fail()) {
     return absl::UnknownError("Failed to write the plan as text.");
   }
-  stream.close();
   return absl::OkStatus();
 }
 
@@ -101,8 +103,10 @@ absl::Status savePlanToProtoText(
     return absl::UnknownError("Failed to save plan as a text protobuf.");
   }
 
+  if (!stream->Close()) {
+    return absl::AbortedError("Failed to close file descriptor.");
+  }
   delete stream;
-  close(outputFileDescriptor);
   return absl::OkStatus();
 }
 
diff --git a/src/substrait/textplan/parser/LoadText.cpp b/src/substrait/textplan/parser/LoadText.cpp
index 0850befe..c76a7b31 100644
--- a/src/substrait/textplan/parser/LoadText.cpp
+++ b/src/substrait/textplan/parser/LoadText.cpp
@@ -2,6 +2,8 @@
 
 #include "substrait/textplan/parser/LoadText.h"
 
+#include <absl/strings/str_join.h>
+
 #include "substrait/proto/plan.pb.h"
 #include "substrait/textplan/StringManipulation.h"
 #include "substrait/textplan/SymbolTablePrinter.h"
@@ -14,7 +16,7 @@ absl::StatusOr<::substrait::proto::Plan> loadFromText(const std::string& text) {
   auto parseResult = io::substrait::textplan::parseStream(stream);
   if (!parseResult.successful()) {
     auto errors = parseResult.getAllErrors();
-    return absl::UnknownError(joinLines(errors));
+    return absl::UnknownError(absl::StrJoin(errors, ""));
   }
 
   return SymbolTablePrinter::outputToBinaryPlan(parseResult.getSymbolTable());