Writing tests

Compiling the counter smart contract

Having the counter smart contract set up, let's first check if the project compiles:

TERMINAL

cargo build

OUTPUT

 Updating crates.io index
  Locking 112 packages to latest compatible versions
    ⋮
Compiling cosmwasm-crypto v2.1.3
Compiling cosmwasm-std v2.1.3
Compiling cw-storage-plus v2.0.0
Compiling counter v0.1.0 (/home/user/my-contracts/counter)
 Finished `dev` profile [unoptimized + debuginfo] target(s) in 3.27s

If the output is similar to the one shown above, it looks like the counter smart contract has been built successfully.

It is a very good habit to run Rust linter (opens in a new tab) after each code change, so let's run it before we move forward.

TERMINAL

cargo clippy

OUTPUT

    ⋮
Checking cosmwasm-crypto v2.1.3
Checking cosmwasm-std v2.1.3
Checking cw-storage-plus v2.0.0
Checking counter v0.1.0 (/home/user/mt-test-examples/mte-counter)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 17.28s

Luckily, clippy reports no issues for the counter smart contract.

Preparing the directory structure for tests

Before we start writing tests, we need to set up the directories and files for the test cases. The final directory and file structure is shown below.

counter (directory)

.
├── Cargo.toml
├── src
│   ├── contract.rs
│   ├── lib.rs
│   └── msg.rs
└── tests
    ├── mod.rs
    └── multitest
        ├── mod.rs
        └── test_counter.rs

💡

There are several configurations possible for placing tests in Rust. For the purpose of this example, we have chosen to place all test cases outside src directory, in a new directory named tests.

💡

Note, that both directories src and tests are placed at the root of the project (in the counter directory).

Let's begin by creating the tests directory:

TERMINAL

mkdir tests

Then create an empty mod.rs file inside the tests directory:

TERMINAL

touch tests/mod.rs

Now, copy and paste the following content to tests/mod.rs file:

tests/mod.rs

mod multitest;

By convention, we place all MultiTest test cases under the multitest directory, so let's create it:

TERMINAL

mkdir tests/multitest

Inside the tests/multitest directory we should also create an empty file named mod.rs:

TERMINAL

touch tests/multitest/mod.rs

And populate it with the following content (just copy and paste it):

tests/multitest/mod.rs

mod test_counter;

Finally, inside the tests/multitest directory, we create a file named test_counter.rs:

TERMINAL

touch tests/multitest/test_counter.rs

For now, we will leave this file empty, but later, we will place all our test cases there.

Now that the directory structure for tests is ready, it's time to run all tests.

Running all tests for counter

Once the directories and files are set up for tests, let's execute them:

TERMINAL

cargo test

The expected output should be similar to the one shown below:

OUTPUT

    Finished `test` profile [unoptimized + debuginfo] target(s) in 17.96s
     Running unittests src/lib.rs (target/debug/deps/counter-f350df45a1cd1c74)
 
running 0 tests
 
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
 
     Running tests/mod.rs (target/debug/deps/mod-54761c1d31e6d0fe)
 
running 0 tests
 
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
 
   Doc-tests counter
 
running 0 tests
 
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Rust testing framework searches for several types of tests in the project, counts all test cases and executes them. In our example - while we haven't written any single test yet - there is nothing to execute. The reported number of executed tests is 0 for unit tests (line 2), 0 for integration tests (line 12) and 0 for documentation tests (line 16).

Similarly, to execute all tests using cargo-nextest (opens in a new tab), type:

TERMINAL

cargo nextest run

The expected output is:

OUTPUT

    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.06s
    Starting 0 tests across 2 binaries (run ID: 3e0cbabb-3ef9-4b2f-98a8-d375bc510845, nextest profile: default)
------------
     Summary [   0.000s] 0 tests run: 0 passed, 0 skipped

cargo-nextest (opens in a new tab) reports in a user-friendly manner that there were no tests to run (line 4).

Now, you have almost everything you need to start testing the counter smart contract. What’s left is to prepare the tools for measuring code coverage, which is a handy way to track progress in writing tests.

Preparing the code coverage script

Typing the entire command for Tarpaulin every time you want to measure current code coverage can be quite tedious, so let's prepare a short script to automate this task.

Create an empty file named coverage.sh in the counter directory:

TERMINAL

touch coverage.sh

Populate it with the following content:

coverage.sh

#!/usr/bin/env bash
 
# generate coverage report
cargo tarpaulin --force-clean --out Html --engine llvm --output-dir "$(pwd)/target/coverage-report"
 
# display link to coverage report
echo "Report: file://$(pwd)/target/coverage-report/tarpaulin-report.html"

Finally, make this file executable:

TERMINAL

chmod +x coverage.sh

The complete file structure of the counter smart contract project, with the code coverage script should now look like this:

TERMINAL

tree

counter (directory)

.
├── Cargo.toml
├── coverage.sh
├── src
│   ├── contract.rs
│   ├── lib.rs
│   └── msg.rs
└── tests
    ├── mod.rs
    └── multitest
        ├── mod.rs
        └── test_counter.rs

Measuring code coverage

With the code coverage script at hand, measuring code coverage is now as simple as typing:

TERMINAL

./coverage.sh

The result should be similar to this (only the last few lines are shown):

OUTPUT

⋮
|| Tested/Total Lines:
|| src/contract.rs: 0/18
||
0.00% coverage, 0/18 lines covered
Report: file:///home/user/counter/target/coverage-report/tarpaulin-report.html

Additionally, Tarpaulin generates a coverage report in HTML format, that can be viewed directly in a browser. As expected, the current code coverage for the counter smart contract is 0.00% since we haven't written any tests yet. Follow the next chapters, and make the code coverage report shine green.

CODE COVERAGE REPORT (CosmWasm version)

 #[cfg(not(feature = "library"))]
 use cosmwasm_std::entry_point;
 
 use crate::msg::{CounterExecMsg, CounterInitMsg, CounterQueryMsg, CounterResponse};
 use cosmwasm_std::{to_json_binary, Binary, Deps, DepsMut, Env, MessageInfo, Response, StdError};
 use cw_storage_plus::Item;
 
 const COUNTER: Item<u8> = Item::new("value");
 
 #[cfg_attr(not(feature = "library"), entry_point)]
 pub fn instantiate(
     deps: DepsMut,
     _env: Env,
     _info: MessageInfo,
     msg: CounterInitMsg,
 ) -> Result<Response, StdError> {
     COUNTER.save(
         deps.storage,
         &match msg {
             CounterInitMsg::Zero => 0,
             CounterInitMsg::Set(new_value) => new_value,
         },
     )?;
     Ok(Response::default())
 }
 
 #[cfg_attr(not(feature = "library"), entry_point)]
 pub fn execute(
     deps: DepsMut,
     _env: Env,
     _info: MessageInfo,
     msg: CounterExecMsg,
 ) -> Result<Response, StdError> {
     COUNTER.update::<_, StdError>(deps.storage, |old_value| {
         Ok(match msg {
             CounterExecMsg::Inc => old_value.saturating_add(1),
             CounterExecMsg::Dec => old_value.saturating_sub(1),
             CounterExecMsg::Set(new_value) => new_value,
         })
     })?;
     Ok(Response::default())
 }
 
 #[cfg_attr(not(feature = "library"), entry_point)]
 pub fn query(deps: Deps, _env: Env, msg: CounterQueryMsg) -> Result<Binary, StdError> {
     match msg {
         CounterQueryMsg::Value => Ok(to_json_binary(&CounterResponse {
             value: COUNTER.may_load(deps.storage)?.unwrap(),
         })?),
     }
 }

CODE COVERAGE REPORT (Sylvia version)

 use crate::msg::{CounterInitMsg, CounterResponse};
 use cosmwasm_std::{Response, StdResult};
 use cw_storage_plus::Item;
 use sylvia::contract;
 use sylvia::ctx::{ExecCtx, InstantiateCtx, QueryCtx};
 
 pub struct CounterContract {
     pub count: Item<u8>,
 }
 
 #[cfg_attr(not(feature = "library"), sylvia::entry_points)]
 #[contract]
 impl CounterContract {
     pub const fn new() -> Self {
         Self {
             count: Item::new("count"),
         }
     }
 
     #[sv::msg(instantiate)]
     fn init(&self, ctx: InstantiateCtx, msg: CounterInitMsg) -> StdResult<Response> {
         match msg {
             CounterInitMsg::Zero => self.count.save(ctx.deps.storage, &0)?,
             CounterInitMsg::Set(value) => self.count.save(ctx.deps.storage, &value)?,
         }
         Ok(Response::new())
     }
 
     #[sv::msg(exec)]
     fn inc(&self, ctx: ExecCtx) -> StdResult<Response> {
         self.count
             .update(ctx.deps.storage, |count| -> StdResult<u8> {
                 Ok(count.saturating_add(1))
             })?;
         Ok(Response::new())
     }
 
     #[sv::msg(exec)]
     fn dec(&self, ctx: ExecCtx) -> StdResult<Response> {
         self.count
             .update(ctx.deps.storage, |count| -> StdResult<u8> {
                 Ok(count.saturating_sub(1))
             })?;
         Ok(Response::new())
     }
 
     #[sv::msg(exec)]
     fn set(&self, ctx: ExecCtx, value: u8) -> StdResult<Response> {
         self.count.save(ctx.deps.storage, &value)?;
         Ok(Response::new())
     }
 
     #[sv::msg(query)]
     fn value(&self, ctx: QueryCtx) -> StdResult<CounterResponse> {
         let value = self.count.load(ctx.deps.storage)?;
         Ok(CounterResponse { value })
     }
 }

Writing tests for smart contracts

Choose the card below to start testing the counter smart contract written using pure CosmWasm libraries or the Sylvia framework.

Writing tests for counter smart contract written using pure CosmWasm libraries Writing tests for counter smart contract written using the Sylvia framework

Sylvia CosmWasm