mvx-scenario-migration

name	mvx-scenario-migration
description	Migrate legacy .scen.json scenario tests to Rust blackbox tests using `sc-meta scen-blackbox`. Use when a MultiversX smart contract project has existing scenario JSON files that need to be converted to the modern typed Rust test format.

Migrating Scenario JSON Tests to Rust Blackbox Tests

Use sc-meta scen-blackbox to auto-generate Rust blackbox tests from existing .scen.json scenario files. The generated code serves as a starting point that must be reviewed and refined before committing.

Running the Generator

sc-meta scen-blackbox

This reads all .scen.json files in the contract's scenarios/ directory and produces a Rust test file.

Generated Code Structure

The generator produces a Rust file with this structure:

use multiversx_sc_scenario::imports::*;

use my_contract::*;

const CODE_PATH: MxscPath = MxscPath::new("output/my-contract.mxsc.json");
const SOME_ADDRESS: TestAddress = TestAddress::new("some-address");
const SOME_SC: TestSCAddress = TestSCAddress::new("some-sc");
const MY_TOKEN: TestTokenId = TestTokenId::new("MYTOKEN-123456");

fn world() -> ScenarioWorld { ... }

#[test]
fn my_scenario_scen() {
    let mut world = world();
    my_scenario_scen_steps(&mut world);
}

pub fn my_scenario_scen_steps(world: &mut ScenarioWorld) {
    // Accounts are set up inline; contracts with pre-existing code skip deploy tx
    world.account(SOME_ADDRESS).nonce(0u64).balance(1_000u64);
    world.account(SOME_SC).nonce(0u64).balance(0u64).code(CODE_PATH);

    world
        .tx()
        .id("my-tx")
        .from(SOME_ADDRESS)
        .to(SOME_SC)
        .typed(my_contract_proxy::MyContractProxy)
        .my_endpoint(arg1, arg2)
        .payment(Payment::try_new(TestTokenId::EGLD_000000, 0, 1_000u64).unwrap())
        // Generator placeholder – replace with a typed value, e.g.:
        // .returns(ExpectValue(42u64))
        .run();
}

Key Observations

• Each scenario file produces one *_scen() test and one pub fn *_scen_steps() function. This separation allows hand-written tests to compose generated step functions for more complex scenarios.
• Accounts with pre-loaded code (i.e., not deployed by the test) are set up via world.account(...).code(CODE_PATH) directly, skipping a deploy transaction.
• All token constants use TestTokenId.
• Payments use Payment::try_new(token_id, nonce, amount).unwrap().
• When the generator cannot infer the return type it emits ScenarioValueRaw as a placeholder. Always replace these with properly typed Rust values before committing the test.
• Transaction IDs exactly mirror the IDs in the .scen.json file; empty IDs ("") are allowed.

Reusing Auto-Generated Steps in Hand-Written Tests

#[test]
fn complex_scenario() {
    let mut world = world();
    // Reuse generated setup
    generated::fund_egld_scen_steps(&mut world);
    // Then add more steps
    world.tx()...run();
}

Required Post-Generation Cleanup

Replace ScenarioValueRaw Placeholders

ScenarioValueRaw is emitted by the auto-generator when it cannot infer the correct Rust return type. It is a placeholder that must be replaced before the test is considered complete:

// ❌ Generator placeholder – needs replacement
// .returns(ExpectValue(ScenarioValueRaw::new("nested:str:EGLD-000000|u64:0|biguint:1000")))

// ✅ After replacement – use a typed value
.returns(ExpectValue(Payment::try_new(TOKEN_ID, 0, 1000u32).unwrap()))

// ✅ Or use a query-based assertion instead
let deposit = world
    .query()
    .to(SC_ADDRESS)
    .typed(my_proxy::MyProxy)
    .get_deposit(&key)
    .returns(ReturnsResultUnmanaged)
    .run();
assert_eq!(deposit.amount, 1000u64);

Auto-Generator Conventions Reference

When reading or writing generated files, these conventions apply:

Element	Convention
Token type	TestTokenId
Per-test function	fn {name}_scen() → calls {name}_scen_steps()
Steps function	pub fn {name}_scen_steps(world: &mut ScenarioWorld)
Account setup	world.account(ADDR).nonce(0u64).balance(100u64)
Payment	Payment::try_new(TOKEN, nonce, amount).unwrap()
Expected return value	ExpectValue(ScenarioValueRaw::new(...)) – placeholder, must be replaced
Error expectation	.with_result(ExpectError(4, "message"))
Transaction ID	mirrors .scen.json step "id" field verbatim (may be "")
Pre-existing SC	world.account(SC_ADDRESS).nonce(0u64).code(CODE_PATH) – no deploy tx