Split the value and pointer edit tests off unit-json_view_edit.cpp

The MinGW linker of the Windows clang jobs cannot link object files with more
than 32767 sections ("relocation truncated to fit: IMAGE_REL_AMD64_REL32
against `.rdata'"). unit-json_view_edit.cpp has 35409 sections since the fast
dump instantiates more code for editable documents, so its test cases "views
and values", "deeply nested values", "pointers below a null value", and
"strings of other documents are checked" move into
unit-json_view_edit_values.cpp. The helper exception_of_call() that both
files use moves into json_view_test_helpers.hpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/src/json_view_test_helpers.hpp

@@ -15,6 +15,7 @@
 #include <nlohmann/json_view.hpp>
 
 #include <algorithm> // any_of
+#include <functional> // function
 #include <random> // mt19937
 #include <string> // string
 
@@ -86,4 +87,20 @@ inline bool has_duplicate_keys(const nlohmann::ordered_json_view& v)
         return e.is_structured() && has_duplicate_keys(e);
     });
 }
+
+#if !defined(JSON_NOEXCEPTION)
+// the exception a call throws, or "" if it throws none
+inline std::string exception_of_call(const std::function<void()>& f)
+{
+    try
+    {
+        f();
+    }
+    catch (const nlohmann::json::exception& e)
+    {
+        return e.what();
+    }
+    return "";
+}
+#endif
 } // namespace json_view_test