test: validate implicit session disallows transactions but supports non-transactional commands

Author: LiamHamsters

src/Ydb.Sdk/test/Ydb.Sdk.Ado.Tests/YdbCommandTests.cs

@@ -249,7 +249,7 @@ public void ImplicitSession_ConcurrentCommand_IsStillBlockedByBusyCheck()
     }
 
     [Fact]
-    public async Task ImplicitSession_WithExplicitTransaction_UsesExplicitSessionAndCommits()
+    public async Task ImplicitSession_DisallowsTransactions_And_AllowsNonTransactionalCommands()
     {
         var table = $"Implicit_{Guid.NewGuid():N}";
 
@@ -271,23 +271,27 @@ PRIMARY KEY (Id)
                 await create.ExecuteNonQueryAsync();
             }
 
-            var tx = connection.BeginTransaction();
             await using (var insert = connection.CreateCommand())
             {
-                insert.Transaction = tx;
                 insert.CommandText = $"INSERT INTO {table} (Id, Name) VALUES (1, 'A');";
                 await insert.ExecuteNonQueryAsync();
-                insert.CommandText = $"INSERT INTO {table} (Id, Name) VALUES (2, 'B');";
-                await insert.ExecuteNonQueryAsync();
             }
 
-            await tx.CommitAsync();
+            var tx = connection.BeginTransaction();
+            await using (var insertTx = connection.CreateCommand())
+            {
+                insertTx.Transaction = tx;
+                insertTx.CommandText = $"INSERT INTO {table} (Id, Name) VALUES (2, 'B');";
+                var ex = await Assert.ThrowsAsync<YdbException>(async () => await insertTx.ExecuteNonQueryAsync());
+                Assert.Contains("Transactions are not supported in implicit sessions", ex.Message);
+            }
+            await tx.RollbackAsync();
 
             await using (var check = connection.CreateCommand())
             {
                 check.CommandText = $"SELECT COUNT(*) FROM {table};";
                 var count = Convert.ToInt32(await check.ExecuteScalarAsync());
-                Assert.Equal(2, count);
+                Assert.Equal(1, count);
             }
         }
         finally