Initial MPI unit tests implementation (#418)

Initial MPI unit tests implementation
diff --git a/examples/mpi/main.cpp b/examples/mpi/main.cpp
new file mode 100644
index 0000000..22db024
--- /dev/null
+++ b/examples/mpi/main.cpp
@@ -0,0 +1,19 @@
+#define DOCTEST_CONFIG_IMPLEMENT
+
+#include <doctest/extensions/doctest_mpi.h>
+
+int main(int argc, char** argv) {
+  MPI_Init(&argc, &argv);
+
+  doctest::Context ctx;
+  ctx.setOption("reporters", "MpiConsoleReporter");
+  ctx.setOption("reporters", "MpiFileReporter");
+  ctx.setOption("force-colors", true);
+  ctx.applyCommandLine(argc, argv);
+
+  int test_result = ctx.run();
+
+  MPI_Finalize();
+
+  return test_result;
+}