Add a small test for DeferredComputation

Author: franzpoeschel

include/openPMD/auxiliary/Future.hpp

@@ -124,7 +124,7 @@ class DeferredComputation
 
     /** Check if the computation is valid
      *
-     * @return true if the computation has not been forgotten
+     * @return true if the computation has not been invalidated
      */
     [[nodiscard]] auto valid() const noexcept -> bool;
 };

src/auxiliary/Future.cpp

@@ -1,4 +1,5 @@
 #include "openPMD/auxiliary/Future.hpp"
+#include "openPMD/Error.hpp"
 #include "openPMD/RecordComponent.hpp"
 
 #include <iostream>
@@ -39,13 +40,13 @@ auto OneTimeTask<T>::operator()() -> T
 {
     if (!members.m_task_valid)
     {
-        throw std::runtime_error(
+        throw error::WrongAPIUsage(
             "[DeferredComputation] No valid state. Probably already "
             "computed.");
     }
     if (!members.m_task)
     {
-        throw std::runtime_error(
+        throw error::WrongAPIUsage(
             "[DeferredComputation] No valid task was specified.");
     }
     members.m_task_valid = false;
@@ -168,6 +169,7 @@ auto DeferredComputation<T>::valid() const noexcept -> bool
 
 template class DeferredComputation<void>;
 template class DeferredComputation<RecordComponent::shared_ptr_dataset_types>;
+template class DeferredComputation<std::string>; // used in tests
 
 // need this for clang-tidy
 #define OPENPMD_ARRAY(type) type[]

test/AuxiliaryTest.cpp

@@ -19,6 +19,8 @@
  * If not, see <http://www.gnu.org/licenses/>.
  */
 // expose private and protected members for invasive testing
+#include "openPMD/Error.hpp"
+#include "openPMD/auxiliary/Future.hpp"
 #if openPMD_USE_INVASIVE_TESTS
 #define OPENPMD_private public:
 #define OPENPMD_protected public:
@@ -538,3 +540,31 @@ TEST_CASE("filesystem_test", "[auxiliary]")
     REQUIRE(!remove_file("./nonexistent_file_in_cmake_bin_directory"));
 #endif
 }
+
+TEST_CASE("future_test", "[auxiliary]")
+{
+    using task_type = auxiliary::DeferredComputation<std::string>;
+    size_t counter = 0;
+
+    auto make_task = [&counter]() {
+        counter = 0;
+        return task_type{[&counter]() {
+            ++counter;
+            return "success";
+        }};
+    };
+
+    auto move_construct = make_task();
+    task_type move_constructed(std::move(move_construct));
+    REQUIRE(counter == 0);
+    REQUIRE(move_constructed() == "success");
+    REQUIRE(counter == 1);
+    REQUIRE_THROWS_AS(move_constructed(), error::WrongAPIUsage);
+
+    auto move_assign = make_task();
+    task_type move_assigned = std::move(move_assign);
+    REQUIRE(counter == 0);
+    REQUIRE(move_assigned() == "success");
+    REQUIRE(counter == 1);
+    REQUIRE_THROWS_AS(move_assigned(), error::WrongAPIUsage);
+}