Testing

The Cosmos SDK contains different types of tests. These tests have different goals and are used at different stages of the development cycle. We advice, as a general rule, to use tests at all stages of the development cycle. It is advised, as a chain developer, to test your application and modules in a similar way than the SDK.

The rationale behind testing can be found in ADR-59.

Unit Tests

Unit tests are the lowest test category of the test pyramid. All packages and modules should have unit test coverage. Modules should have their dependencies mocked: this means mocking keepers.

The SDK uses mockgen to generate mocks for keepers:

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/scripts/mockgen.sh#L3-L6

You can read more about mockgen here.

Example

As an example, we will walkthrough the keeper tests of the x/gov module.

The x/gov module has a Keeper type, which requires a few external dependencies (ie. imports outside x/gov to work properly).

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/gov/keeper/keeper.go#L22-L24

In order to only test x/gov, we mock the expected keepers and instantiate the Keeper with the mocked dependencies. Note that we may need to configure the mocked dependencies to return the expected values:

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/gov/keeper/common_test.go#L67-L81

This allows us to test the x/gov module without having to import other modules.

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/gov/keeper/keeper_test.go#L3-L42

We can test then create unit tests using the newly created Keeper instance.

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/x/gov/keeper/keeper_test.go#L83-L107

Integration Tests

Integration tests are at the second level of the test pyramid. In the SDK, we locate our integration tests under /tests/integrations.

The goal of these integration tests is to test how a component interacts with other dependencies. Compared to unit tests, integration tests do not mock dependencies. Instead, they use the direct dependencies of the component. This differs as well from end-to-end tests, which test the component with a full application.

Integration tests interact with the tested module via the defined Msg and Query services. The result of the test can be verified by checking the state of the application, by checking the emitted events or the response. It is advised to combine two of these methods to verify the result of the test.

The SDK provides small helpers for quickly setting up an integration tests. These helpers can be found at https://github.com/cosmos/cosmos-sdk/blob/main/testutil/integration.

Example

https://github.com/cosmos/cosmos-sdk/blob/a2f73a7dd37bea0ab303792c55fa1e4e1db3b898/testutil/integration/example_test.go#L30-L116

Deterministic and Regression tests

Tests are written for queries in the Cosmos SDK which have module_query_safe Protobuf annotation.

Each query is tested using 2 methods:

• Use property-based testing with the rapid library. The property that is tested is that the query response and gas consumption are the same upon 1000 query calls.
• Regression tests are written with hardcoded responses and gas, and verify they don't change upon 1000 calls and between SDK patch versions.

Here's an example of regression tests:

https://github.com/cosmos/cosmos-sdk/blob/v0.50.0-alpha.0/tests/integration/bank/keeper/deterministic_test.go#L134-L151

Simulations

Simulations fuzz tests for deterministic message execution. They use a minimal application, built with depinject:

note

Simulations have been refactored to message factories

An example for x/bank/ simulations:

https://github.com/cosmos/cosmos-sdk/blob/release/v0.52.x/x/bank/simulation/msg_factory.go#L13-L20

System Tests

System tests are at the top of the test pyramid. They test the whole application flow as black box, from the user perspective. They are located under /tests/systemtests.

For that, the SDK is using the simapp binary, but you should use your own binary. More details about system test can be found in building-apps

Learn More

Learn more about testing scope in ADR-59.