Stabilize nightly mutation targets and fault injection

test/distributed_test.exs

@@ -5717,16 +5717,21 @@ defmodule Group.DistributedTest do
       :ok = TestCluster.rpc!(node_a, Group, :disconnect, [name, "tenant/transient"])
       :ok = TestCluster.rpc!(node_a, Group, :connect, [name, "tenant/after-close"])
 
-      {:messages, queued_messages} =
-        TestCluster.rpc!(node_b, Process, :info, [receiver, :messages])
+      queued_controls = fn ->
+        {:messages, queued_messages} =
+          TestCluster.rpc!(node_b, Process, :info, [receiver, :messages])
 
-      queued_controls =
         for {kind, remote_pid, _generation, revision, _epochs} <- queued_messages,
             kind in [:replica_cluster_open, :replica_cluster_close],
             node(remote_pid) == node_a,
             do: {kind, revision}
+      end
+
+      # Local connect completion does not order a separate RPC to the receiver
+      # after delivery of the sender's distribution messages.
+      TestCluster.assert_eventually(fn -> length(queued_controls.()) == 3 end)
 
-      assert queued_controls == [
+      assert queued_controls.() == [
                {:replica_cluster_open, 33},
                {:replica_cluster_close, 34},
                {:replica_cluster_open, 35}

test/mutation/README.md

@@ -35,9 +35,11 @@ and runs the designated real multi-node regression. A compiling mutant is
 `killed` only when the regression fails. Any surviving or non-compiling mutant
 makes the campaign fail.
 Before either listing or running mutants, it also requires every production
-replacement to match exactly once and every test selector to point at the test
-declaration itself. Source edits therefore fail loudly instead of turning a
-stale mutation into a placebo run of an adjacent test.
+replacement to match exactly once. Test selectors pair a file with a literal
+test/property name, resolved to its current declaration line before execution.
+Moving a test requires no selector update; missing or ambiguous names fail
+instead of turning a stale mutation into a placebo run of an adjacent test.
+The local PR gate validates all definitions without running the campaign.
 
 ```bash
 mix run --no-start test/mutation/run.exs

test/mutation/isolation_test.exs

@@ -8,6 +8,7 @@ defmodule Group.MutationIsolationTest do
 
   @repo Path.expand("../..", __DIR__)
   @mutation "drain_oversized_ingress_batch_without_yield"
+  @target "an oversized incoming batch yields to an already queued local write"
 
   setup do
     work = Path.join(@repo, "tmp/mutation-isolation-#{System.unique_integer([:positive])}")
@@ -71,7 +72,7 @@ defmodule Group.MutationIsolationTest do
     assert output =~ "#{@mutation}: SURVIVED"
     refute File.exists?(Path.join(work, "checker-invocations"))
 
-    {output, status} = command(work, ["mix", "test", "test/group_test.exs:34"])
+    {output, status} = command(work, ["mix", "test", "test/group_test.exs"])
     assert status != 0, output
     assert File.read!(Path.join(work, "checker-invocations")) == "invoked\n"
   end
@@ -108,13 +109,49 @@ defmodule Group.MutationIsolationTest do
     refute output =~ "#{@mutation}: killed"
   end
 
+  test "selectors follow a moved declaration without running adjacent tests", %{work: work} do
+    target(work, "assert Isolation.Target.split([1, 2]) == {[1], [2]}")
+    path = Path.join(work, "test/group_test.exs")
+
+    File.write!(
+      path,
+      String.replace(
+        File.read!(path),
+        "  use ExUnit.Case\n",
+        "  use ExUnit.Case\n\n  test \"not the target\", do: flunk(\"must not be selected\")\n\n"
+      )
+    )
+
+    {output, status} = campaign(work)
+    assert status == 0, output
+    assert output =~ "#{@mutation}: killed"
+  end
+
+  test "missing and ambiguous names fail before running a baseline", %{work: work} do
+    for {name, copies, count} <- [{"renamed target", 1, 0}, {@target, 2, 2}] do
+      declarations = String.duplicate("  test #{inspect(name)}, do: assert(true)\n", copies)
+      write(work, "test/group_test.exs", "defmodule TargetTest do\n#{declarations}end\n")
+
+      {output, status} = campaign(work)
+      assert status != 0, output
+      assert output =~ "must match exactly one test/property declaration"
+      assert output =~ "(found #{count})"
+      refute output =~ "baseline "
+    end
+  end
+
   defp target(work, assertion) do
     write(
       work,
       "test/group_test.exs",
-      "defmodule Isolation.TargetTest do\n  use ExUnit.Case\n" <>
-        String.duplicate("\n", 31) <>
-        "  test \"target\" do\n    #{assertion}\n  end\nend\n"
+      """
+      defmodule Isolation.TargetTest do
+        use ExUnit.Case
+        test #{inspect(@target)} do
+          #{assertion}
+        end
+      end
+      """
     )
   end