cosmos-sdk/CODING_GUIDELINES.md

Coding Guidelines

This document is an extension to CONTRIBUTING and provides more details about the coding guidelines and requirements.

API & Design

• Code must be well structured:
  • packages must have a limited responsibility (different concerns can go to different packages),
  • types must be easy to compose,
  • think about maintainbility and testability.
• "Depend upon abstractions, [not] concretions".
• Try to limit the number of methods you are exposing. It's easier to expose something later than to hide it.
• Take advantage of internal package concept.
• Follow agreed-upon design patterns and naming conventions.
• publicly-exposed functions are named logically, have forward-thinking arguments and return types.
• Avoid global variables and global configurators.
• Favor composable and extensible designs.
• Minimize code duplication.
• Limit third-party dependencies.

Performance:

• Avoid unnecessary operations or memory allocations.

Security:

• Pay proper attention to exploits involving:
  • gas usage
  • transaction verification and signatures
  • malleability
  • code must be always deterministic
• Thread safety. If some functionality is not thread-safe, or uses something that is not thread-safe, then clearly indicate the risk on each level.

Testing

Make sure your code is well tested:

• Provide unit tests for every unit of your code if possible. Unit tests are expected to comprise 70%-80% of your tests.
• Describe the test scenarios you are implementing for integration tests.
• Create integration tests for queries and msgs.
• Use both test cases and property / fuzzy testing. We use the rapid Go library for property-based and fuzzy testing.
• Do not decrease code test coverage. Explain in a PR if test coverage is decreased.

We expect tests to use require or assert rather than t.Skip or t.Fail, unless there is a reason to do otherwise. When testing a function under a variety of different inputs, we prefer to use table driven tests. Table driven test error messages should follow the following format <desc>, tc #<index>, i #<index>. <desc> is an optional short description of whats failing, tc is the index within the test case table that is failing, and i is when there is a loop, exactly which iteration of the loop failed. The idea is you should be able to see the error message and figure out exactly what failed. Here is an example check:

<some table>
for tcIndex, tc := range cases {
  <some code>
  resp, err := doSomething()
  require.NoError(err)
  require.Equal(t, tc.expected, resp, "should correctly perform X")

Quality Assurance

We are forming a QA team that will support the core Cosmos SDK team and collaborators by:

• Improving the Cosmos SDK QA Processes
• Improving automation in QA and testing
• Defining high-quality metrics
• Maintaining and improving testing frameworks (unit tests, integration tests, and functional tests)
• Defining test scenarios.
• Verifying user experience and defining a high quality.
  • We want to have acceptance tests! Document and list acceptance lists that are implemented and identify acceptance tests that are still missing.
  • Acceptance tests should be specified in acceptance-tests directory as Markdown files.
• Supporting other teams with testing frameworks, automation, and User Experience testing.
• Testing chain upgrades for every new breaking change.
  • Defining automated tests that assure data integrity after an update.

Desired outcomes:

• QA team works with Development Team.
• QA is happening in parallel with Core Cosmos SDK development.
• Releases are more predictable.
• QA reports. Goal is to guide with new tasks and be one of the QA measures.

As a developer, you must help the QA team by providing instructions for User Experience (UX) and functional testing.