fix: pytest promote_or_fail implementation

The assertion `status == "Leader"` was in the first place, and
`raft_timeout_now` call was unreachable.

test/int/conftest.py

@@ -283,11 +283,20 @@ class Instance:
         assert status.is_ready()
         self.raft_id = status.id
 
-    @funcy.retry(tries=20, timeout=0.1)
+    @funcy.retry(tries=4, timeout=0.1, errors=AssertionError)
     def promote_or_fail(self):
-        self.assert_raft_status("Leader")
+        eprint(f"{self} is trying to become a leader")
+
+        # 1. Force the node to campaign.
         self.call("picolib.raft_timeout_now")
 
+        # 2. Wait until the miracle occurs.
+        @funcy.retry(tries=4, timeout=0.1, errors=AssertionError)
+        def wait_promoted():
+            assert self.__raft_status() == "Leader"
+
+        wait_promoted()
+
 
 @dataclass
 class Cluster:

test/int/test_couple.py

@@ -25,6 +25,19 @@ def test_follower_proposal(cluster2: Cluster):
     assert i2.eval("return check") == i2.listen
 
 
+def test_switchover(cluster2: Cluster):
+    i1, i2 = cluster2.instances
+
+    i1.promote_or_fail()
+    i1.assert_raft_status("Leader")
+
+    i2.promote_or_fail()
+    i2.assert_raft_status("Leader")
+
+    # Check idempotency
+    i2.promote_or_fail()
+
+
 def test_failover(cluster2: Cluster):
     i1, i2 = cluster2.instances
     i1.promote_or_fail()