Replace platform-specific code with std::filesystem in MBTiles test (#2634)

platform/android/DEVELOPING.md

@@ -45,9 +45,17 @@ To run the instrumentation tests, choose the "Instrumentation Tests" run configu
 
 Your device needs remain unlocked for the duration of the tests.
 
+## C++ Unit Tests
+
+There is a separate Gradle project that contains a test app which runs the C++ Unit Tests. It does not depend on the Android platform implementations.
+
+You can find the project in `test/android.` You can open this project in Android Studio and run the C++ Tests on an Android device or Simulator.
+
+To run a particular set of tests you can modify the `--gtest_filter` flag in `platform/android/src/test/test_runner.cpp`. See the [GoogleTest documentation](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) for details how to use this flag.
+
 ### AWS Device Farm
 
-The instrumentation tests are running on AWS Device Farm. To see the results and the logs, go to:
+The instrumentation tests and C++ unit tests are running on AWS Device Farm. To see the results and the logs, go to:
 
 https://us-west-2.console.aws.amazon.com/devicefarm/home?region=us-east-1#/mobile/projects/20687d72-0e46-403e-8f03-0941850665bc/runs
 

test/storage/mbtiles_file_source.test.cpp

@@ -4,30 +4,16 @@
 #include <mbgl/util/platform.hpp>
 #include <mbgl/util/run_loop.hpp>
 
+#include <filesystem>
+
 #include <climits>
 #include <gtest/gtest.h>
 
-#if defined(WIN32)
-#include <Windows.h>
-#ifndef PATH_MAX
-#define PATH_MAX MAX_PATH
-#endif /* PATH_MAX */
-#else
-#include <unistd.h>
-#endif
-
 namespace {
 
 std::string toAbsoluteURL(const std::string &fileName) {
-    char buff[PATH_MAX + 1];
-#ifdef _MSC_VER
-    char *cwd = _getcwd(buff, PATH_MAX + 1);
-#else
-    char *cwd = getcwd(buff, PATH_MAX + 1);
-#endif
-    std::string url = {"mbtiles://" + std::string(cwd) + "/test/fixtures/storage/mbtiles/" + fileName};
-    assert(url.size() <= PATH_MAX);
-    return url;
+    auto path = std::filesystem::current_path() / "test/fixtures/storage/mbtiles" / fileName;
+    return "mbtiles://" + std::string(path);
 }
 
 } // namespace