Tests: added tests with abstract UNIX sockets.

test/unit/check/unix_abstract.py

@@ -0,0 +1,25 @@
+import json
+
+from unit.http import TestHTTP
+from unit.option import option
+
+http = TestHTTP()
+
+
+def check_unix_abstract():
+    available = option.available
+
+    resp = http.put(
+        url='/config',
+        sock_type='unix',
+        addr=option.temp_dir + '/control.unit.sock',
+        body=json.dumps(
+            {
+                "listeners": {"unix:@sock": {"pass": "routes"}},
+                "routes": [],
+            }
+        ),
+    )
+
+    if 'success' in resp['body']:
+        available['features']['unix_abstract'] = True