Check additional return values in some test cases
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 620c368..239f8a9 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -101,6 +101,7 @@
     mpi_init( &X );
 
     file = fopen( input_file, "r" );
+    TEST_ASSERT( file != NULL );
     TEST_ASSERT( mpi_read_file( &X, radix_X, file ) == result );
     fclose(file);