implemented the first version of statement_cache

test/orm/sql/StatementCacheTest.cpp

@@ -0,0 +1,36 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include <matador/query/query.hpp>
+
+#include "matador/sql/connection_pool.hpp"
+#include "matador/sql/statement_cache.hpp"
+
+#include "../backend/test_backend_service.hpp"
+
+#include "ConnectionPoolFixture.hpp"
+
+using namespace matador::test;
+using namespace matador::sql;
+using namespace matador::query;
+
+TEST_CASE("Test statement cache", "[statement][cache]") {
+  backend_provider::instance().register_backend("noop", std::make_unique<orm::test_backend_service>());
+
+  connection_pool pool("noop://noop.db", 4);
+  statement_cache cache(pool, 4);
+
+  query_context ctx;
+  ctx.sql = "SELECT * FROM person";
+
+  REQUIRE(cache.capacity() == 4);
+  REQUIRE(cache.empty());
+
+  auto result = cache.acquire(ctx);
+  REQUIRE(result);
+
+  REQUIRE(cache.size() == 1);
+  REQUIRE(!cache.empty());
+  REQUIRE(cache.capacity() == 4);
+
+  const auto stmt = result.value();
+}