diff --git a/xCAT-test/unit/nodediscover_default_netboot.t b/xCAT-test/unit/nodediscover_default_netboot.t
new file mode 100644
index 000000000..39641171d
--- /dev/null
+++ b/xCAT-test/unit/nodediscover_default_netboot.t
@@ -0,0 +1,86 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+## no critic (Modules::RequireFilenameMatchesPackage)
+
+use FindBin;
+use File::Spec;
+use Test::More;
+
+# nodediscover sets noderes.netboot for a freshly discovered node when the
+# admin did not pick a method that fits the reported architecture. The ladder
+# lives in _default_netboot() so it can be checked without a database: stub
+# the modules the plugin loads at compile time and call the helper directly.
+
+BEGIN {
+    package xCAT::Table;
+    $INC{'xCAT/Table.pm'} = __FILE__;
+
+    package xCAT::Utils;
+    $INC{'xCAT/Utils.pm'} = __FILE__;
+
+    package XML::Simple;
+    sub import { }
+    $INC{'XML/Simple.pm'} = __FILE__;
+
+    package xCAT::data::switchinfo;
+    our %global_mac_identity;
+    $INC{'xCAT/data/switchinfo.pm'} = __FILE__;
+
+    package xCAT::DiscoveryUtils;
+    $INC{'xCAT/DiscoveryUtils.pm'} = __FILE__;
+}
+
+my $repo_root = File::Spec->catdir( $FindBin::Bin, '..', '..' );
+my $plugin = File::Spec->catfile( $repo_root, 'xCAT-server', 'lib', 'xcat', 'plugins', 'nodediscover.pm' );
+plan skip_all => "$plugin not found" unless -r $plugin;
+
+require $plugin;
+
+my $warnings = 0;
+local $SIG{__WARN__} = sub { $warnings++; diag(@_) };
+
+sub default_netboot {
+    return xCAT_plugin::nodediscover::_default_netboot(@_);
+}
+
+# riscv64: UEFI + grub2 only
+is( default_netboot( 'riscv64', '', '' ),           'grub2', 'riscv64 nodes default to grub2' );
+is( default_netboot( 'riscv64', undef, undef ),     'grub2', 'riscv64 defaults to grub2 when no platform or netboot was reported' );
+is( default_netboot( 'riscv64', '', 'xnba' ),       'grub2', 'a riscv64 node with an x86 method is corrected to grub2' );
+is( default_netboot( 'riscv64', '', 'grub2' ),      undef,   'riscv64 keeps an explicit grub2 method' );
+is( default_netboot( 'riscv64', '', 'grub2-http' ), undef,   'riscv64 keeps grub2-http' );
+is( default_netboot( 'riscv64', '', 'grub2-tftp' ), undef,   'riscv64 keeps grub2-tftp' );
+is( default_netboot( 'riscv32', '', '' ),           undef,   'riscv32 is not treated as riscv64' );
+
+# existing architectures keep their behavior
+is( default_netboot( 'x86_64', '', '' ),       'xnba',      'x86_64 nodes default to xnba' );
+is( default_netboot( 'x86_64', '', 'pxe' ),    undef,       'x86_64 keeps pxe' );
+is( default_netboot( 'x86_64', '', 'xnba' ),   undef,       'x86_64 keeps xnba' );
+is( default_netboot( 'x86', '', 'grub2' ),     'xnba',      'x86 with a non-x86 method is corrected to xnba' );
+is( default_netboot( 'ppc64le', 'PowerNV', '' ),          'petitboot', 'PowerNV nodes default to petitboot' );
+is( default_netboot( 'ppc64le', 'PowerNV', 'petitboot' ), 'petitboot', 'PowerNV nodes are always set to petitboot' );
+is( default_netboot( 'ppc64', 'pSeries', '' ),        'yaboot', 'non-PowerNV ppc nodes default to yaboot' );
+is( default_netboot( 'ppc64', 'pSeries', 'yaboot' ),  undef,    'ppc nodes keep yaboot' );
+is( default_netboot( 'armv7l', '', '' ),      'onie', 'armv7l switches default to onie' );
+is( default_netboot( 'armv7l', '', 'onie' ),  undef,  'armv7l keeps onie' );
+is( default_netboot( 'aarch64', '', '' ),     undef,  'aarch64 is left untouched, as before' );
+is( default_netboot( undef, undef, undef ),   undef,  'a missing arch sets nothing' );
+
+is( $warnings, 0, 'no warnings were emitted for undefined inputs' );
+
+# The discovery request is stored as discovery data key by key, so reading the platform
+# of a node that never reported one must not add the key to the request.
+my $source = do { open( my $fh, '<', $plugin ) or die "Unable to read $plugin: $!"; local $/; <$fh> };
+like(
+    $source,
+    qr/my \$platform = exists \$request->\{platform\} \? \$request->\{platform\}->\[0\] : undef;/,
+    'the netboot ladder only reads the platform of a request that carries one',
+);
+unlike(
+    $source,
+    qr/_default_netboot\(\s*\$request->\{arch\}->\[0\],\s*\$request->\{platform\}->\[0\]/,
+    'the netboot ladder does not autovivify the platform key of the discovery request',
+);
+
+done_testing();