add a few more unit tests for functions in utils

unittest/utils/test_utils.cpp

@@ -15,6 +15,9 @@
 #include "gmock/gmock.h"
 #include "utils.h"
 #include <string>
+#include <cerrno>
+#include <cstdio>
+#include <cstdlib>
 
 using namespace LAMMPS_NS;
 using ::testing::Eq;
@@ -223,3 +226,35 @@ TEST(Utils, path_basename) {
     ASSERT_THAT(utils::path_basename("/parent/folder/filename"), Eq("filename"));
 #endif
 }
+
+TEST(Utils, getsyserror) {
+#if defined(__linux__)
+    errno = ENOENT;
+    std::string errmesg = utils::getsyserror();
+    ASSERT_THAT(errmesg, Eq("No such file or directory"));
+#else
+    GTEST_SKIP();
+#endif
+}
+
+TEST(Utils, potential_file) {
+    FILE *fp;
+    fp = fopen("ctest.txt","w");
+    ASSERT_NE(fp,nullptr);
+    fputs("# DATE: 2020-02-20 CONTRIBUTOR: Nessuno\n",fp);
+    fclose(fp);
+
+    EXPECT_TRUE(utils::file_is_readable("ctest.txt"));
+    EXPECT_FALSE(utils::file_is_readable("no_such_file.txt"));
+
+    EXPECT_THAT(utils::get_potential_file_path("ctest.txt"),Eq("ctest.txt"));
+    const char *folder = getenv("LAMMPS_POTENTIALS");
+    if (folder != nullptr) {
+      std::string path=utils::path_join(folder,"Cu_u3.eam");
+      EXPECT_THAT(utils::get_potential_file_path("Cu_u3.eam"),Eq(path));
+    }
+
+    EXPECT_THAT(utils::get_potential_date("ctest.txt","Test"),Eq("2020-02-20"));
+
+    remove("ctest.txt");
+}