Explain Your First Test
  • 10 Apr 2024
  • 4 Minutes to read
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Explain Your First Test

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  • PDF

Article Summary

It's time to focus on testing. Thorough testing is essential to ensuring the proper predictable working of any Scrypto packages we write. You may have noticed an example of this in the Hello template used in several previous sections. It has a test/ directory that holds a lib.rs file containing two test functions. These demonstrate two ways to test the Hello blueprint and the two main ways to test any Scrypto package. Here we'll explain both and show you how to run the tests.

The scrypto package referenced in this section can be found in our official examples here.


Testing Blueprints and Modules

There are two ways to test blueprints and modules, the TestRunner and Scrypto-Test. The TestRunner is better suited for integration testing, while Scrypto-Test is more ideal for unit testing.


The TestRunner is an in-memory ledger simulator. Tests interact with the simulator as a user submitting transactions to the network would. This is great for integration and end-to-end testing.

To test with the TestRunner, we import scrypto::this_package and the currently poorly named (and soon to be renamed) scrypto_unit at the top of our test file:

use scrypto::this_package;
use scrypto_unit::*;

To make this import work, we need to add scrypto_unit to the Cargo.toml file:

# --snip--
scrypto-unit = { git = "https://github.com/radixdlt/radixdlt-scrypto", tag = "v1.1.1" }

Where we also need to make sure the test feature is enabled:

default = []
test = []

Then we can create our ledger simulator environment. In our case that's back in
the test/lib.rs file inside the test_hello function:

fn test_hello() {
    // Setup the environment
    let mut test_runner = TestRunnerBuilder::new().build();

In that environment, we create an account:

    // Create an account
    let (public_key, _private_key, account) = test_runner.new_allocated_account();

We then need the package available in the environment:

    // Publish package
    let package_address = test_runner.compile_and_publish(this_package!());

Once we have the package we can test the instantiate function. This is done by:

  1. Building a manifest with the the ManifestBuilder:

        let manifest = ManifestBuilder::new()
  2. Submitting the manifest to the ledger:

        let receipt = test_runner.execute_manifest_ignoring_fee(
  3. Checking the manifest receipt to see if it successfully instantiated a new component, then storing the component address for later use if it did:

        let component = receipt.expect_commit(true).new_component_addresses()[0];

With the component in our test environment and its address, we can now test the free_token method. A similar 3 steps are followed, but with a different manifest:

  1. Build a manifest:

     let manifest = ManifestBuilder::new()
         .call_method(component, "free_token", manifest_args!())
  2. Submit the manifest to the ledger:

     let receipt = test_runner.execute_manifest_ignoring_fee(
  3. Check the manifest receipt to see if it was successful:


We do not need to check the return value of the free_token method as we are testing the ledger interaction, not the logic of the method. If the method returns an error, the test will fail. Testing the logic of the method is more
easily done with Scrypto-Test.


The Scrypto-Test framework is different to the Test Runner. Instead of interacting with the ledger as a user, tests interact as native blueprints. This removes the need for transaction manifests and opens up some extra options unavailable with TestRunner. These differences make it better suited for unit testing the logic of a blueprint.

Testing our Hello blueprint with Scrypto-Test is done with the scrypto::this_package macro, scrypto_test::prelude and hello_test::test_bindings modules:

use scrypto::this_package;
use scrypto_test::prelude::*;
use hello_test::test_bindings::*;

scrypto-test and hello-test also need to be added to the Cargo.toml file's dev-dependencies, hello-test with the test feature enabled:

# --snip--
scrypto-test = { git = "https://github.com/radixdlt/radixdlt-scrypto", tag = "v1.1.1" }
# --snip--
hello-test = { path = ".", features = ["test"] }

Adding hello-test itself allows us to use its auto generated test_bindings
module. Without adding the test feature, the module will not be generated.

The test feature also needs to be enabled for Scrypto-Test, the same way it
was for the TestRunner:

default = []
test = []

We'll use the Scrypto-Test framework to test the free_token method output with
a AAA testing pattern: Arrange, Act, Assert.

In our test/lib.rs file, with the modules imported we create a new environment
and arrange the conditions for our test by publishing our package and
instantiating a new Hello component from it - no manifest required:

// Arrange
    let mut env = TestEnvironment::new();
    let package_address = Package::compile_and_publish(this_package!(), &mut env)?;

    let mut hello = Hello::instantiate_hello(package_address, &mut env)?;

This allows us to then perform the action we want to test by calling the method:

    // Act
    let bucket = hello.free_token(&mut env)?;

The method returns whatever it would on ledger; in this case a bucket. We can
now check the amount of tokens in the bucket is what we expect with an

    // Assert
    let amount = bucket.amount(&mut env)?;
    assert_eq!(amount, dec!("1"));

If the assertion is incorrect the test will panic and the test will fail. If the
assertion is correct we can return an Ok (containing an empty value):


If you're wondering about the new syntax, Scrypto-Test uses
Result return types for error
handling, so we can use the ? operator to propagate errors up the call stack,
and OK to return the function values. In our case we're just returning Ok(()),
with an empty value, to indicate the test passed and propagated errors are
handled by the test framework.

Running the Tests

Running tests on a scrypto package is simple just follow the instructions here in our Official Examples on GitHub

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