Add better error handling of test

lib/resdata/tests/rd_grid_dx_dy_dz.cpp

@@ -4,21 +4,33 @@
 #include <math.h>
 
 #include <string>
+#include <filesystem>
+#include <iostream>
 
 #include <ert/util/test_util.hpp>
 #include <ert/util/util.h>
 
 #include <resdata/rd_grid.hpp>
 #include <resdata/rd_file.hpp>
 
+namespace fs = std::filesystem;
+
 double err(double a, double b) { return (a - b) / a; }
 
 void test_dxdydz(const std::string &grid_fname, const std::string &init_fname) {
     double eps_x = 1e-4;
     double eps_y = 1e-4;
     double eps_z = 1e-3;
     rd_grid_type *grid = rd_grid_alloc(grid_fname.c_str());
+    if (grid == NULL) {
+        std::cerr << "Could not open " << grid_fname << std::endl;
+        exit(-1);
+    }
     rd_file_type *init_file = rd_file_open(init_fname.c_str(), 0);
+    if (init_file == NULL) {
+        std::cerr << "Could not open " << init_fname << std::endl;
+        exit(-1);
+    }
     rd_kw_type *dx = rd_file_iget_named_kw(init_file, "DX", 0);
     rd_kw_type *dy = rd_file_iget_named_kw(init_file, "DY", 0);
     rd_kw_type *dz = rd_file_iget_named_kw(init_file, "DZ", 0);
@@ -46,9 +58,19 @@ void test_dxdydz(const std::string &grid_fname, const std::string &init_fname) {
 }
 
 int main(int argc, char **argv) {
+    if (argc < 2) {
+        std::cerr << "Must give case as input" << std::endl;
+        exit(-1);
+    }
     const std::string rd_case = argv[1];
-    std::string grid_file = rd_case + ".EGRID";
-    std::string init_file = rd_case + ".INIT";
+    fs::path grid_file = rd_case + ".EGRID";
+    fs::path init_file = rd_case + ".INIT";
+
+    if (!fs::exists(grid_file) || !fs::exists(init_file)) {
+        std::cerr << "Given case " << rd_case << " without grid or init"
+                  << std::endl;
+        exit(-1);
+    }
 
     test_dxdydz(grid_file, init_file);