test: Add tests for GetArg methods / settings.json type coercion

Just add tests. No changes to application behavior. Tests will be
updated in the next commit changing & improving current behavior.

Include a Qt test for GUI startup crash reported by Rspigler in
https://github.com/bitcoin/bitcoin/issues/24457 caused by GetArg
behavior that happens if settings.json contains an integer value for any
of the configuration options which GUI settings can currently clash with
(-dbcache, -par, -spendzeroconfchange, -signer, -upnp, -natpmp, -listen,
-server, -proxy, -proxy, -onion, -onion, -lang, and -prune).

1 files changed, 31 insertions, 0 deletions

diff --git a/src/qt/test/optiontests.cpp b/src/qt/test/optiontests.cpp
new file mode 100644
index 0000000000..80d8d77984
--- /dev/null
+++ b/src/qt/test/optiontests.cpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <qt/bitcoin.h>
+#include <qt/test/optiontests.h>
+#include <test/util/setup_common.h>
+#include <util/system.h>
+
+#include <QSettings>
+#include <QTest>
+
+#include <univalue.h>
+
+//! Entry point for BitcoinApplication tests.
+void OptionTests::optionTests()
+{
+    // Test regression https://github.com/bitcoin/bitcoin/issues/24457. Check
+    // if setting an integer prune value causes an exception to be thrown in
+    // the OptionsModel constructor.
+    gArgs.LockSettings([&](util::Settings& settings) {
+        settings.forced_settings.erase("prune");
+        settings.rw_settings["prune"] = 3814;
+    });
+    gArgs.WriteSettingsFile();
+    QVERIFY_EXCEPTION_THROWN(OptionsModel{}, std::runtime_error);
+    gArgs.LockSettings([&](util::Settings& settings) {
+        settings.rw_settings.erase("prune");
+    });
+    gArgs.WriteSettingsFile();
+}