diff --git a/tests/test-trusted.py b/tests/test-trusted.py
--- a/tests/test-trusted.py
+++ b/tests/test-trusted.py
@@ -9,7 +9,7 @@ from mercurial import ui, util
 hgrc = os.environ['HGRCPATH']
 
 def testui(user='foo', group='bar', tusers=(), tgroups=(),
-           cuser='foo', cgroup='bar', debug=False):
+           cuser='foo', cgroup='bar', debug=False, silent=False):
     # user, group => owners of the file
     # tusers, tgroups => trusted users/groups
     # cuser, cgroup => user/group of the current process
@@ -56,8 +56,18 @@ def testui(user='foo', group='bar', tuse
     parentui.updateopts(debug=debug)
     u = ui.ui(parentui=parentui)
     u.readconfig('.hg/hgrc')
+    if silent:
+        return u
+    print 'trusted'
     for name, path in u.configitems('paths'):
         print '   ', name, '=', path
+    print 'untrusted'
+    for name, path in u.configitems('paths', untrusted=True):
+        print '.',
+        u.config('paths', name) # warning with debug=True
+        print '.',
+        u.config('paths', name, untrusted=True) # no warnings
+        print name, '=', path
     print
 
     return u
@@ -68,6 +78,7 @@ os.mkdir('.hg')
 f = open('.hg/hgrc', 'w')
 f.write('[paths]\n')
 f.write('local = /another/path\n\n')
+f.write('interpolated = %(global)s%(local)s\n\n')
 f.close()
 
 #print '# Everything is run by user foo, group bar\n'
@@ -111,3 +122,83 @@ testui(user='abc', group='def', tusers=[
 
 print "# Can't figure out the name of the user running this process"
 testui(user='abc', group='def', cuser=None)
+
+print "# prints debug warnings"
+u = testui(user='abc', group='def', cuser='foo', debug=True)
+
+print "# ui.readsections"
+filename = 'foobar'
+f = open(filename, 'w')
+f.write('[foobar]\n')
+f.write('baz = quux\n')
+f.close()
+u.readsections(filename, 'foobar')
+print u.config('foobar', 'baz')
+
+print
+print "# read trusted, untrusted, new ui, trusted"
+u = ui.ui()
+u.updateopts(debug=True)
+u.readconfig(filename)
+u2 = ui.ui(parentui=u)
+def username(uid=None):
+    return 'foo'
+util.username = username
+u2.readconfig('.hg/hgrc')
+print 'trusted:'
+print u2.config('foobar', 'baz')
+print u2.config('paths', 'interpolated')
+print 'untrusted:'
+print u2.config('foobar', 'baz', untrusted=True)
+print u2.config('paths', 'interpolated', untrusted=True)
+
+print 
+print "# error handling"
+
+def assertraises(f, exc=util.Abort):
+    try:
+        f()
+    except exc, inst:
+        print 'raised', inst.__class__.__name__
+    else:
+        print 'no exception?!'
+
+print "# file doesn't exist"
+os.unlink('.hg/hgrc')
+assert not os.path.exists('.hg/hgrc')
+testui(debug=True, silent=True)
+testui(user='abc', group='def', debug=True, silent=True)
+
+print
+print "# parse error"
+f = open('.hg/hgrc', 'w')
+f.write('foo = bar')
+f.close()
+testui(user='abc', group='def', silent=True)
+assertraises(lambda: testui(debug=True, silent=True))
+
+print
+print "# interpolation error"
+f = open('.hg/hgrc', 'w')
+f.write('[foo]\n')
+f.write('bar = %(')
+f.close()
+u = testui(debug=True, silent=True)
+print '# regular config:'
+print '  trusted',
+assertraises(lambda: u.config('foo', 'bar'))
+print 'untrusted',
+assertraises(lambda: u.config('foo', 'bar', untrusted=True))
+
+u = testui(user='abc', group='def', debug=True, silent=True)
+print '  trusted ',
+print u.config('foo', 'bar')
+print 'untrusted',
+assertraises(lambda: u.config('foo', 'bar', untrusted=True))
+
+print '# configitems:'
+print '  trusted ',
+print u.configitems('foo')
+print 'untrusted',
+assertraises(lambda: u.configitems('foo', untrusted=True))
+