fix flap test: wait for closing execQuery stream from server (#243)

Author: KirillKurdyukov

src/Ydb.Sdk/tests/Ado/YdbCommandTests.cs

@@ -280,6 +280,10 @@ public void ExecuteDbDataReader_WhenPreviousIsNotClosed_ThrowException()
 
         Assert.Equal("A command is already in progress: SELECT 1; SELECT 1;",
             Assert.Throws<YdbOperationInProgressException>(() => dbCommand.ExecuteReader()).Message);
+        Assert.True(ydbDataReader.NextResult());
+        Assert.True(ydbDataReader.NextResult());
+        Assert.False(ydbDataReader.NextResult());
+
         ydbDataReader.Close();
         Assert.True(ydbDataReader.IsClosed);
     }
@@ -331,6 +335,7 @@ public void GetChars_WhenSelectText_MoveCharsToBuffer()
         Assert.Equal(checkBuffer, bufferChars);
 
         Assert.Equal('a', ydbDataReader.GetChar(0));
+        Assert.False(ydbDataReader.Read());
     }
 
     [Fact]
@@ -377,6 +382,7 @@ public void GetBytes_WhenSelectBytes_MoveBytesToBuffer()
         checkBuffer[6] = (byte)'b';
         checkBuffer[7] = (byte)'a';
         Assert.Equal(checkBuffer, bufferChars);
+        Assert.False(ydbDataReader.Read());
     }
 
     [Fact]

src/Ydb.Sdk/tests/Ado/YdbTransactionTests.cs

@@ -137,6 +137,11 @@ public void CommitAndRollback_WhenStreamIsOpened_ThrowException()
         Assert.Equal("A command is already in progress: SELECT 1; SELECT 2; SELECT 3",
             Assert.Throws<YdbOperationInProgressException>(() => ydbTransaction.Rollback()).Message);
 
+        Assert.True(dbDataReader.NextResult());
+        Assert.True(dbDataReader.NextResult());
+        Assert.True(dbDataReader.NextResult());
+        Assert.False(dbDataReader.NextResult());
+
         dbDataReader.Close(); // Close stream
         ydbTransaction.Commit();
         Assert.Equal("This YdbTransaction has completed; it is no longer usable",