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How to Test a Vara Program


Vara uses the standard testing mechanism for Rust programs: building and running testing executables using cargo.

Following the basic concepts and testing methods described in the Rustbook, tests can be organized into two main categories: unit tests and integration tests.

Unit tests enable testing of each unit of code in isolation from the rest of the code. This helps quickly identify where the code works as expected and where it does not. Unit tests should be placed in the src directory in each file containing the code they test.

Even when code units work correctly, it is crucial to test if several library parts work together correctly. For integration tests, a separate tests directory is required at the top level of the project directory, next to src. Multiple test files can be created in this directory, and cargo will compile each file as an individual crate.

How to Test a Program

There are at least two ways to test and debug Vara programs.

The first is off-chain testing using the low-level gtest crate. This approach is recommended for unit and integration tests.

The second is on-chain testing with the higher-level gclient crate, which is well-suited for end-to-end testing.

Although gclient is oriented towards end-to-end testing, tests can be written as unit or integration tests in Rust. It is recommended to use an integration-like approach with separate test files in the tests directory when utilizing the gclient crate.

Building a Program in Test Mode

First, ensure a compiled Wasm file of the program to be tested. Refer to Getting Started for additional details.

  1. Usually, the following command is used for the regular compilation of Vara programs:

    cd ~/gear/contracts/first-gear-app/
    cargo build --release

    The nightly compiler is required if some unstable features have been used:

    cargo +nightly build --release
  2. The minimal command for running tests is:

    cargo test

    The nightly compiler is required if the program uses unstable Rust features, and the compiler will prompt to enable nightly if necessary:

    cargo +nightly test

    Build tests in release mode to run faster:

    cargo test --release

Dig Deeper

The following sections outline testing a Vara program using both the gtest and gclient crates.