Stop relying on byteme::temp_file_path for tests.

It's simple enough to write ourselves so there's no need to incur a dependency
on byteme's semi-internal testing functions.

tests/src/load_matrix.cpp

@@ -1,11 +1,11 @@
 #include <gtest/gtest.h>
 
 #include "byteme/byteme.hpp"
-#include "byteme/temp_file_path.hpp"
 #include "eminem/eminem.hpp"
 #include "tatami_test/tatami_test.hpp"
 
 #include "tatami_mtx/tatami_mtx.hpp"
+#include "temp_file_path.h"
 
 #include <limits>
 #include <fstream>
@@ -142,7 +142,7 @@ TEST_F(LoadMatrixInputTest, SimpleBuffer) {
 TEST_F(LoadMatrixInputTest, SimpleText) {
     initialize(100, 99, 59);
 
-    auto path = byteme::temp_file_path("tatami-tests-ext-MatrixMarket", ".mtx");
+    auto path = temp_file_path("tatami-tests-ext-MatrixMarket");
     byteme::RawFileWriter writer(path.c_str());
     write_coordinate(writer);
 
@@ -201,7 +201,7 @@ TEST_F(LoadMatrixInputTest, ZlibBuffer) {
 TEST_F(LoadMatrixInputTest, GzipFile) {
     initialize(102, 200, 100);
 
-    auto path = byteme::temp_file_path("tatami-tests-ext-MatrixMarket", ".mtx.gz");
+    auto path = temp_file_path("tatami-tests-ext-MatrixMarket");
     byteme::GzipFileWriter writer(path.c_str());
     write_coordinate(writer);
 

tests/src/temp_file_path.h

@@ -0,0 +1,23 @@
+#ifndef TEMP_FILE_PATH_H
+#define TEMP_FILE_PATH_H
+
+#include <filesystem>
+#include <random>
+#include <string>
+
+inline std::string temp_file_path(const std::string& prefix) {
+    auto path = std::filesystem::temp_directory_path();
+    path.append(prefix);
+
+    std::random_device rd;
+    std::mt19937_64 rng(rd());
+    std::filesystem::path full;
+    do {
+        full = path;
+        full += std::to_string(rng());
+    } while (std::filesystem::exists(full));
+
+    return full;
+}
+
+#endif