Add first tests.

test/CMakeLists.txt

@@ -22,6 +22,7 @@ add_executable(
   unit_tests/container/generic_data_handle.cpp
   unit_tests/container/mechanism.cpp
   unit_tests/container/node.cpp
+  unit_tests/utils/enumerate.cpp
   unit_tests/oc/hoc_interpreter.cpp)
 set(catch2_targets testneuron)
 if(NRN_ENABLE_THREADS)

test/unit_tests/utils/enumerate.cpp

@@ -0,0 +1,39 @@
+// Must appear before `enumerate.h` otherwise, std::begin and std::rbegin are
+// undefined. This should be fixed by including the correct headers in
+// `utils/enumerate.h`.
+#include <vector>
+
+#include "utils/enumerate.h"
+
+#include <catch2/catch.hpp>
+
+
+
+TEST_CASE("reverse", "[Neuron]") {
+  std::vector<double> x{1.0, 2.0, 3.0};
+
+  // test/unit_tests/utils/enumerate.cpp:15:26: error: cannot bind non-const
+  // lvalue reference of type ‘double&’ to an rvalue of type ‘double’
+  // 15 |   for(auto& i : reverse(x)) {
+  //    |                          ^
+
+  // for(auto& i : reverse(x)) {
+  //     i *= -1.0;
+  // }
+
+}
+
+TEST_CASE("reverse; no-copy", "[Neuron]") {
+  std::vector<double> x{1.0, 2.0, 3.0};
+
+  auto reverse_iterable = reverse(x);
+
+  for(auto& xx : x) {
+    xx *= -1.0;
+  }
+
+  size_t i = 0;
+  for(const auto& xx : reverse_iterable) {
+      REQUIRE(xx < 0.0);
+  }
+}