Squashed 'third_party/immer/' content from commit ad3e3556d

git-subtree-dir: third_party/immer
git-subtree-split: ad3e3556d38bb75966dd24c61a774970a7c7957e

test/box/generic.ipp

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+//
+// immer: immutable data structures for C++
+// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
+//
+// This software is distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
+//
+
+#ifndef BOX_T
+#error "define the box template to use in BOX_T"
+#endif
+
+#include <catch.hpp>
+
+TEST_CASE("construction and copy")
+{
+    auto x = BOX_T<int>{};
+    CHECK(x == 0);
+
+    auto y = x;
+    CHECK(&x.get() == &y.get());
+
+    auto z = std::move(x);
+    CHECK(&z.get() == &y.get());
+}
+
+TEST_CASE("equality")
+{
+    auto x = BOX_T<int>{};
+    auto y = x;
+    CHECK(x == 0.0f);
+    CHECK(x == y);
+    CHECK(x == BOX_T<int>{});
+    CHECK(x != BOX_T<int>{42});
+}
+
+TEST_CASE("update")
+{
+    auto x = BOX_T<int>{};
+    auto y = x.update([](auto v) { return v + 1; });
+    CHECK(x == 0);
+    CHECK(y == 1);
+}
+
+TEST_CASE("update move")
+{
+    auto x    = BOX_T<int>{};
+    auto addr = &x.get();
+    auto y    = std::move(x).update(
+        [](auto&& v) { return std::forward<decltype(v)>(v) + 1; });
+
+    CHECK(y == 1);
+    if (std::is_empty<typename BOX_T<int>::memory_policy::refcount>::value) {
+        CHECK(&y.get() != addr);
+    } else {
+        CHECK(&y.get() == addr);
+    }
+}