diff --git a/xCAT-test/unit/genesis_dhcp_client.t b/xCAT-test/unit/genesis_dhcp_client.t
new file mode 100644
index 000000000..e50ccae40
--- /dev/null
+++ b/xCAT-test/unit/genesis_dhcp_client.t
@@ -0,0 +1,163 @@
+#!/usr/bin/env perl
+# Drive the DHCP client selection out of doxcat.
+#
+# doxcat cannot be sourced: it restarts rsyslogd, reads /proc/cmdline and ends in a loop that
+# waits for an address. Extract the two routines and run them with the clients shadowed by
+# stubs that record their own argv.
+use strict;
+use warnings;
+
+use File::Path qw(make_path);
+use File::Slurper qw(read_text write_text);
+use File::Temp qw(tempdir);
+use FindBin;
+use lib "$FindBin::Bin/../lib";
+use Test::More;
+
+use XCAT::Test::File qw(repo_path);
+
+my $DOXCAT = 'xCAT-genesis-scripts/usr/bin/doxcat';
+my $ISC4   = 'dhclient -cf /etc/dhclient.conf -pf /var/run/dhclient.eth0.pid eth0';
+my $ISC6   = 'dhclient -6 -pf /var/run/dhclient6.eth0.pid eth0 -lf /var/lib/dhclient/dhclient6.leases';
+
+my $source = read_text( repo_path($DOXCAT) );
+my $tmpdir = tempdir( CLEANUP => 1 );
+
+# The failure this captures: doxcat named dhclient at six call sites, so on a release that
+# packages no ISC client Genesis reported "dhclient: command not found" and no node ever got
+# an address.
+ok( $source !~ qr/^\s*dhclient\s/m,
+    'doxcat starts no command line with dhclient' );
+ok( $source !~ qr/;\s*dhclient\s/,
+    'doxcat chains no command line into dhclient' );
+
+# The build root has to carry a client, or the image installs none. EL8 and EL9 package the
+# ISC client; AlmaLinux 10 baseos packages dhcpcd.
+my $spec = read_text( repo_path('xCAT-genesis-builder/xCAT-genesis-base.spec') );
+like( $spec, qr/^%if 0%\{\?rhel\} >= 10\nBuildRequires: dhcpcd$/m,
+    'the spec build-requires dhcpcd on the releases that drop the ISC client' );
+
+# The payload check has to name the client the release ships, or the build passes with no
+# client in the image again.
+like( $spec, qr{^%if 0%\{\?rhel\} >= 10\nGENESIS_REQUIRED="usr/sbin/dhcpcd"$}m,
+    'the payload check requires dhcpcd on the releases that drop the ISC client' );
+
+# dracut_install reports a missing binary and returns, so naming dhclient alone shipped an
+# image with no client at all.
+my $module = read_text( repo_path('xCAT-genesis-builder/dracut_105/el/module-setup.sh') );
+ok( $module !~ qr/^\s*dracut_install dhclient lldpad$/m,
+    'the dracut module no longer installs dhclient unconditionally' );
+like( $module, qr/^\s*dracut_install dhcpcd$/m,
+    'the dracut module installs dhcpcd when the build root carries it' );
+like( $module, qr{^\s*dracut_install /usr/libexec/dhcpcd-run-hooks$}m,
+    'the dracut module installs the hooks dhcpcd runs on every lease' );
+
+my $selector = extract_function( $source, 'genesis_dhcp_command' );
+my $runner   = extract_function( $source, 'genesis_start_dhcp' );
+
+if ( !defined $selector || !defined $runner ) {
+    fail('doxcat carries genesis_dhcp_command() to choose the client');
+    fail('doxcat carries genesis_start_dhcp() to run the chosen client');
+    done_testing();
+    exit 0;
+}
+
+# EL8 and EL9 package the ISC client, and it stays the one Genesis uses there.
+is( selected( 4, ['dhclient'] ), $ISC4, 'the ISC client keeps its IPv4 command line' );
+is( selected( 6, ['dhclient'] ), $ISC6, 'the ISC client keeps its IPv6 command line' );
+is( selected( 4, [ 'dhclient', 'dhcpcd' ] ), $ISC4,
+    'the ISC client is preferred when the image carries both' );
+
+# RHEL 10 packages no ISC client. AlmaLinux 10 baseos packages dhcpcd, which carries its own
+# resolv.conf, hostname and ntp hooks, so it needs no dhclient-script.
+is( selected( 4, ['dhcpcd'] ), 'dhcpcd -4 -b -p -t 0 eth0',
+    'dhcpcd stands in for dhclient on IPv4' );
+is( selected( 6, ['dhcpcd'] ), 'dhcpcd -6 -b -p -t 0 eth0',
+    'dhcpcd stands in for dhclient on IPv6' );
+
+# dhcpcd on a single interface exits when its timeout expires, and the default is 30 seconds.
+# doxcat waits for the lease for as long as it takes, so the client must not give up first.
+like( selected( 4, ['dhcpcd'] ), qr/(?:^|\s)-t 0(?:\s|$)/,
+    'dhcpcd is asked to wait for a lease instead of timing out' );
+
+# dhcpcd de-configures the interface when it exits unless it is persistent. Genesis keeps the
+# address it was given.
+like( selected( 4, ['dhcpcd'] ), qr/(?:^|\s)-p(?:\s|$)/,
+    'dhcpcd is asked to leave the address in place' );
+
+# An image with no client at all has to say so rather than run an empty command line.
+is( selected( 4, [] ), '', 'nothing is chosen when the image carries no client' );
+
+# The runner is what the call sites use, so it has to actually execute the chosen client.
+is( started( 4, ['dhcpcd'] ), 'dhcpcd -4 -b -p -t 0 eth0',
+    'genesis_start_dhcp runs dhcpcd when it is the only client' );
+is( started( 4, ['dhclient'] ), $ISC4,
+    'genesis_start_dhcp runs the ISC client when it is there' );
+is( started( 4, [] ), '',
+    'genesis_start_dhcp runs no client when the image carries none' );
+isnt( start_status( 4, [] ), 0,
+    'genesis_start_dhcp reports failure when the image carries no client' );
+
+done_testing();
+
+#---
+# extract_function: lift one shell function out of a script that cannot be sourced.
+# Returns undef when the function is absent, so the caller fails the assertion instead of
+# bailing out of a suite that has already found the defect.
+#---
+sub extract_function {
+    my ( $text, $name ) = @_;
+    my ($body) = $text =~ /^($name\(\)\s*\{.*?^\})$/ms;
+    return $body;
+}
+
+#---
+# probe: run the extracted routines with only the named clients on PATH.
+# Returns the standard output, the recorded argv of whatever ran, and the exit status.
+#---
+sub probe {
+    my ( $call, $clients ) = @_;
+    my $dir = tempdir( DIR => $tmpdir, CLEANUP => 1 );
+    my $bin = "$dir/bin";
+    make_path($bin);
+
+    # PATH holds the stubs alone, so each one names itself rather than calling basename.
+    my $record = "$dir/record";
+    foreach my $client ( @{$clients} ) {
+        write_text( "$bin/$client",
+            qq{#!/bin/sh\necho "$client \$*" >> "$record"\nexit 0\n} );
+        chmod 0755, "$bin/$client";
+    }
+
+    # logger writes to the console in the image and is not what these assertions measure.
+    write_text( "$bin/logger", "#!/bin/sh\nexit 0\n" );
+    chmod 0755, "$bin/logger";
+
+    write_text( "$dir/probe.sh", "log_label=test\n$selector\n$runner\n$call\n" );
+    my $out = `PATH="$bin" /bin/bash "$dir/probe.sh" 2>/dev/null`;
+    my $status = $? >> 8;
+    chomp $out;
+
+    my $ran = -e $record ? read_text($record) : '';
+    chomp $ran;
+
+    return ( $out, $ran, $status );
+}
+
+sub selected {
+    my ( $family, $clients ) = @_;
+    my ( $out, undef, undef ) = probe( qq{genesis_dhcp_command $family eth0}, $clients );
+    return $out;
+}
+
+sub started {
+    my ( $family, $clients ) = @_;
+    my ( undef, $ran, undef ) = probe( qq{genesis_start_dhcp $family eth0}, $clients );
+    return $ran;
+}
+
+sub start_status {
+    my ( $family, $clients ) = @_;
+    my ( undef, undef, $status ) = probe( qq{genesis_start_dhcp $family eth0}, $clients );
+    return $status;
+}