diff --git a/xCAT-test/unit/rspconfig_per_bmc_argument.t b/xCAT-test/unit/rspconfig_per_bmc_argument.t
new file mode 100644
index 000000000..51b9bc0c0
--- /dev/null
+++ b/xCAT-test/unit/rspconfig_per_bmc_argument.t
@@ -0,0 +1,78 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use File::Spec;
+use Test::More;
+
+my $plugin = File::Spec->catfile( $FindBin::Bin, '..', '..',
+    'xCAT-server', 'lib', 'xcat', 'plugins', 'ipmi.pm' );
+plan skip_all => 'ipmi.pm not found' unless -r $plugin;
+
+open( my $fh, '<', $plugin ) or die "Unable to read $plugin: $!";
+my $source = do { local $/; <$fh> };
+close($fh);
+
+# ipmi.pm cannot be loaded here, so lift out the routine and drive the real
+# code on its own.
+my ($routine) = $source =~ /(sub per_bmc_argument \{.*?\n\}\n)/s;
+my ($gate)    = $source =~ /(my %per_bmc_subcommand = map.*?;)/s;
+BAIL_OUT('could not extract per_bmc_argument from ipmi.pm') unless $routine;
+BAIL_OUT('could not extract the per BMC subcommand set from ipmi.pm') unless $gate;
+eval "package BmcArg; $gate $routine sub gate { return \\%per_bmc_subcommand } 1;"
+  or BAIL_OUT("could not evaluate per_bmc_argument: $@");
+
+sub pick { return BmcArg::per_bmc_argument(@_); }
+my $per_bmc = BmcArg::gate();
+
+# A single value reaches every BMC, which is what a node with one BMC needs
+# and what every existing command line looks like.
+is( pick( '10.0.0.5', 1 ), '10.0.0.5', 'a single value serves the first BMC' );
+is( pick( '10.0.0.5', 2 ), '10.0.0.5', 'a single value serves a later BMC too' );
+
+# A list gives one setting per BMC, in session order.
+is( pick( '10.0.0.5,10.0.0.6', 1 ), '10.0.0.5', 'the first BMC takes the first value' );
+is( pick( '10.0.0.5,10.0.0.6', 2 ), '10.0.0.6', 'the second BMC takes the second value' );
+is( pick( '10.0.0.5,10.0.0.6,10.0.0.7', 3 ), '10.0.0.7', 'the third BMC takes the third value' );
+
+# A list too short reports nothing rather than an empty setting, so the caller
+# can tell the operator instead of writing a blank value into a BMC.
+is( pick( '10.0.0.5,10.0.0.6', 3 ), undef, 'a list shorter than the BMC number yields nothing' );
+
+# An empty element carries no setting, so it reads as missing rather than
+# reaching the address encoders, which reject an empty string outright.
+is( pick( '10.0.0.5,', 2 ), undef, 'an empty element yields nothing' );
+is( pick( ',10.0.0.6', 1 ), undef, 'a leading empty element yields nothing' );
+
+# Defensive input.
+is( pick( undef, 1 ), undef, 'an undefined argument stays undefined' );
+is( pick( '10.0.0.5,10.0.0.6' ), '10.0.0.5', 'a missing BMC number reads as the first' );
+is( pick( '10.0.0.5,10.0.0.6', 0 ), '10.0.0.5', 'a zero BMC number reads as the first' );
+
+# The netmask and gateway settings travel the same path.
+is( pick( '255.255.255.0,255.255.254.0', 2 ), '255.255.254.0', 'a netmask list follows the BMC number' );
+
+# Only the settings the man page advertises take a list. Every other
+# subcommand keeps its argument whole, because a comma can belong to the value,
+# as it does in a free form SNMP community string.
+ok( $per_bmc->{$_},  "$_ takes one value per BMC" )      for qw(ip netmask gateway);
+ok( !$per_bmc->{$_}, "$_ keeps its argument whole" )     for qw(community snmpdest alert garp thermprofile);
+
+like( $source, qr/if \(\$per_bmc_subcommand\{\$subcommand\} and \$argument =~ \/,\/\)/,
+    'the caller splits only the settings that take a list' );
+
+# The follow-up callbacks read the subcommand again, so the session has to hold
+# the value of its own BMC by then.
+like( $source, qr/\$sessdata->\{subcommand\} = "\$subcommand=\$argument";/,
+    'the session keeps the value of its own BMC for the follow-up' );
+
+# The caller reports the mismatch rather than sending an empty setting, and
+# the thermal profile keeps its own argument.
+like( $source,
+    qr/unless \(defined \$bmcvalue\) \{\s*\n\s*\$callback->\(\{ errorcode => \[1\], error => \["The value \$argument does not carry a setting for BMC/,
+    'the caller reports a short list instead of sending it' );
+like( $source, qr/if \(\$subcommand eq "thermprofile"\) \{\n\s*return idpxthermprofile\(\$argument\);/,
+    'the thermal profile is answered before the per BMC split' );
+
+done_testing();