Add tests

Author: maltoe

test/bitcrowd_ecto/repo_test.exs

@@ -102,13 +102,16 @@ defmodule BitcrowdEcto.RepoTest do
       assert TestRepo.fetch_by(query, []) == {:ok, resource}
     end
 
-    # The actual lock is non-trivial to test, I tried.
     test "can lock for :update", %{resource: %{id: id} = resource} do
-      assert TestRepo.fetch_by(TestSchema, [id: id], lock: :update) == {:ok, resource}
+      assert_lock_granted("relation = 'test_schema_pkey'::regclass::oid", fn ->
+        assert TestRepo.fetch_by(TestSchema, [id: id], lock: :update) == {:ok, resource}
+      end)
     end
 
     test "can lock for :no_key_update", %{resource: %{id: id} = resource} do
-      assert TestRepo.fetch_by(TestSchema, [id: id], lock: :no_key_update) == {:ok, resource}
+      assert_lock_granted("relation = 'test_schema_pkey'::regclass::oid", fn ->
+        assert TestRepo.fetch_by(TestSchema, [id: id], lock: :no_key_update) == {:ok, resource}
+      end)
     end
 
     test "converts CastErrors for binary_id columns to not_found errors" do
@@ -161,4 +164,41 @@ defmodule BitcrowdEcto.RepoTest do
       assert TestRepo.fetch_by(TestSchema, [id: resource.id], prefix: prefix) == {:ok, resource}
     end
   end
+
+  describe "advisory_xact_lock/1" do
+    test "acquires an advisory lock" do
+      assert_lock_granted("locktype = 'advisory'", fn ->
+        TestRepo.advisory_xact_lock("foo")
+      end)
+    end
+
+    test "accepts atoms" do
+      assert_lock_granted("locktype = 'advisory'", fn ->
+        TestRepo.advisory_xact_lock(:foo)
+      end)
+    end
+  end
+
+  defp assert_lock_granted(where, fun) do
+    assert locks_granted(where) == 0
+    result = fun.()
+    assert locks_granted(where) == 1
+    result
+  end
+
+  defp locks_granted(where) do
+    %{rows: [[vxid]]} =
+      TestRepo.query!("""
+      SELECT virtualtransaction FROM pg_locks
+      WHERE transactionid::text = (txid_current() % (2^32)::bigint)::text;
+      """)
+
+    %{rows: [[count]]} =
+      TestRepo.query!("""
+      SELECT COUNT(*) FROM pg_locks
+      WHERE virtualtransaction = '#{vxid}' AND granted IS TRUE AND #{where};
+      """)
+
+    count
+  end
 end