tests: Add param --bin to specify the binrary path

Default is to use the system installed version, in $PATH.

tests/test.py

@@ -36,12 +36,13 @@ parser.add_argument('-b', '--server-args', type=str, default=None)
 parser.add_argument('--should-fail', action='store_true', default=None)
 parser.add_argument('--url', type=str, default=default_url)
 parser.add_argument('--dns', type=str, default='8.8.8.8')
+parser.add_argument('--bin', type=str, default='')
 
 config = parser.parse_args()
 
-client_args = ['src/ss-local', '-v']
-server_args = ['src/ss-server', '-v', '-u']
-tunnel_args = ['src/ss-tunnel', '-v', '-u', '-l1082', '-L%s:53' % config.dns]
+client_args = ['%s%s' % (config.bin, 'ss-local'), '-v']
+server_args = ['%s%s' % (config.bin, 'ss-server'), '-v', '-u']
+tunnel_args = ['%s%s' % (config.bin, 'ss-tunnel'), '-v', '-u', '-l1082', '-L%s:53' % config.dns]
 
 if config.client_conf:
     client_args.extend(['-c', config.client_conf])