According to Vedomosti, closed testing of the Telegram blockchain has started 
12.04.19
A limited number of teams of professionals received from Telegram access to the test version of the TON blockchain. This is what Vedomosti reports with reference to the statements of the leaders of two companies participating in the testing. 

Commands that have access to the TON testnet can already set up a network node. According to sources, it’s still premature to talk about concrete results. They refused to disclose other details. Another interviewee said that "testing will allow you to study the properties and network readiness, which transactions and at what speed it will be able to conduct." 

Alexander Filatov, Managing Director of the developer tools company TON.labs, chose not to comment on TON testing. 

The possibility of a quick launch of the TON test network became known in early February. According to the development documents, the overall project readiness at that time was estimated by its creators to be 90%. The TON virtual machine was 95% ready, while the work on “basic smart contracts and their samples” was completed only by 20%. As the developers themselves explain in the submitted documents, their current priority is to launch a test network with the support of the simplest smart contracts. 

In the same month, information was leaked to the network indicating that the agreements for the purchase of TON Gram’s own tokens could be canceled if the project is not launched before October 31, 2019.