dbclient obeys $HOME, but dropbear (the server) resolves HOME using getpwnam.
Use sys-libs/nss_wrapper to fake it during tests.

--- a/test/Makefile.in
+++ b/test/Makefile.in
@@ -4,7 +4,15 @@ SHELL=bash
 
 all: test
 
+uid:=$(shell id -u)
+gid:=$(shell id -g)
 test: fakekey
+	mkdir -p ~/.ssh
+	../dropbearkey -t ecdsa -f ~/.ssh/id_dropbear
+	../dropbearkey -y -f ~/.ssh/id_dropbear | grep ^ecdsa > ~/.ssh/authorized_keys
+	echo "$(LOGNAME)::$(uid):$(gid):$(USER):$(HOME):/bin/bash" >> ~/passwd
+	echo "$(LOGNAME)::$(gid):" >> ~/group
+	chmod 0700 ~ ~/.ssh ~/.ssh/authorized_keys ~/passwd ~/group
 	pytest --hostkey=fakekey --dbclient=../dbclient --dropbear=../dropbear $(srcdir)
 
 one: fakekey
--- a/test/test_dropbear.py
+++ b/test/test_dropbear.py
@@ -27,7 +27,11 @@ def dropbear(request):
 		]
 	print("subprocess args: ", args)
 
-	p = subprocess.Popen(args, stderr=subprocess.PIPE, text=True)
+	env = os.environ
+	env['LD_PRELOAD'] = 'libnss_wrapper.so'
+	env['NSS_WRAPPER_PASSWD'] = env['HOME'] + '/passwd'
+	env['NSS_WRAPPER_GROUP'] = env['HOME'] + '/group'
+	p = subprocess.Popen(args, stderr=subprocess.PIPE, text=True, env=env)
 	# Wait until it has started listening
 	for l in p.stderr:
 		if "Not backgrounding" in l: