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Testing with gtest

gtest simulates a real network by providing mockups of the user, program, balances, mailbox, etc. Since it does not include parts of the actual blockchain, it is fast and lightweight. However, as a model of the blockchain network, gtest cannot be a complete reflection of the actual network.

gtest is excellent for unit and integration testing and is also helpful for debugging Vara program logic. Running tests based on gtest only requires the Rust compiler, making its use in continuous integration predictable and robust.

Import gtest Library

To use the gtest library, import it into the Cargo.toml file in the [dev-dependencies] block to fetch and compile it for tests only:

name = "first-gear-app"
version = "0.1.0"
authors = ["Your Name"]
edition = "2021"

gstd = { git = "", tag = "v1.1.1" }

gear-wasm-builder = { git = "", tag = "v1.1.1" }

gtest = { git = "", tag = "v1.1.1" }

gtest Capabilities

  • Initialization of the common environment for running programs:
// This emulates node's and chain's behavior.
// By default, sets:
// - current block equals 0
// - current timestamp equals UNIX timestamp of your system.
// - minimal message id equal 0x010000..
// - minimal program id equal 0x010000..
let sys = System::new();
  • Program initialization:
// Initialization of program structure from file.
// Takes as arguments reference to the related `System` and the path to wasm binary relative to the root of the crate where the test was written.
// Sets free program id from the related `System` to this program. For this case it equals 0x010000..
// Next program initialized without id specification will have id 0x020000.. and so on.
let _ = Program::from_file(

// Also, use the `Program::current()` function to load the current program.
let _ = Program::current(&sys);

// Check the id of the program by calling `id()` function.
// It returns `ProgramId` type value.
let ping_pong_id =;

// Manually specify the id of the program using `from_file_with_id` constructor.
let _ = ProgramBuilder::from_file("./target/wasm32-unknown-unknown/release/demo_ping.wasm")
  • Getting the program from the system:
// Retrieve the object from the system by id.
let _ = sys.get_program(105);
  • Initialization of styled env_logger:
// Initialization of styled `env_logger` to print logs (only from `gwasm` by default) into stdout.
// To specify printed logs, set the env variable `RUST_LOG`:
// `RUST_LOG="target_1=logging_level,target_2=logging_level" cargo test`
// Vara programs use `gwasm` target with `debug` logging level
  • Sending messages:
// To send a message to the program, call `send()` or `send_bytes()` (or `send_with_value` and `send_bytes_with_value` if you need to send a message with attached funds).
// Both methods require the sender id as the first argument and the payload as the second.
// The first method requires payload to be CODEC Encodable, while the second requires payload to implement `AsRef<[u8]>`.
// First message to the initialized program structure is always the init message.
let res = program.send_bytes(100001, "INIT MESSAGE");
  • Processing the result of the program execution:
// Sending functions return `RunResult` structure containing the final result of the processing message and others created during execution.
// It has 4 main functions:

// Returns the reference to the Vec produced to users messages.

// Returns bool indicating if there was panic during the execution of the main message.

// Returns bool indicating if there was panic during the execution of the created messages during the main execution.

// Returns bool indicating if logs contain a given log.

// Build a log for assertion using `Log` structure with its builders.
// All fields are optional. Assertions with Logs from core are made on the Some(..) fields.
// Constructor for success log.
let _ = Log::builder();

// Constructor for error reply log. Note that error reply never contains payload.
let _ = Log::error_builder();

// Send a new message after the program has been initialized.
let res = ping_pong.send_bytes(100001, "PING");

// Other fields are set optionally by `dest()`, `source()`, `payload()`, `payload_bytes()`.
// The logic for `payload()` and `payload_bytes()` is the same as for `send()` and `send_bytes()`.
let log = Log::builder()


let wrong_log = Log::builder().source(100001);


// Log also has `From` implementations from (ID, T) and from (ID, ID, T),
// where ID: Into<ProgramIdWrapper>, T: AsRef<[u8]>.
// Examples:
let x = Log::builder().dest(5).payload_bytes("A");
let x_from: Log = (5, "A").into();
assert_eq!(x, x_from);

let y = Log::builder().dest(5).source(15).payload_bytes("A");
let y_from: Log = (15, 5, "A").into();
assert_eq!(y, y_from);

assert!(!res.contains(&(ping_pong_id, ping_pong_id, "PONG")));
assert!(res.contains(&(1, 100001, "PONG")));
  • Spending blocks:
// Control time in the system by spending blocks.
// It adds the amount of blocks passed as arguments to the current block of the system.
// Note that 1 block in Vara network is 1 sec duration.
  • Balance:
// To send a message with value, mint balance for the message sender:
let user_id = 42;
sys.mint_to(user_id, 5000);
assert_eq!(sys.balance_of(user_id), 5000);

// To give the balance to the program, use the `mint` method:
let prog = Program::current(&sys);;
assert_eq!(prog.balance(), 1000);