docs: Coverage check section in DEVELOPMENT.md

.gitignore

@@ -16,4 +16,9 @@ devenv.local.nix
 
 # direnv
 .direnv
-.pre-commit-config.yaml
+.pre-commit-config.yaml
+
+# Coverage reports
+.coverage
+coverage.xml
+lcov.info

DEVELOPMENT.md

@@ -95,6 +95,24 @@ We also check for clippy warnings, which are a set of linting rules for rust. To
 cargo clippy --all-targets
 ```
 
+## 📈 Code Coverage
+
+We run coverage checks on the CI. Once you submit a PR, you can review the
+line-by-line coverage report on
+[codecov](https://app.codecov.io/gh/CQCL/tket2/commits?branch=All%20branches).
+
+To run the rust coverage checks locally, install `cargo-llvm-cov`, generate the report with:
+```bash
+cargo llvm-cov --lcov > lcov.info
+```
+and open it with your favourite coverage viewer. In VSCode, you can use
+[`coverage-gutters`](https://marketplace.visualstudio.com/items?itemName=ryanluker.vscode-coverage-gutters).
+
+Similarly, to run the python coverage checks locally, install `pytest-cov` and run:
+```bash
+pytest --cov=./ --cov-report=xml
+```
+
 ## 🌐 Contributing to tket2
 
 We welcome contributions to tket2! Please open [an issue](https://github.com/CQCL/tket2/issues/new) or [pull request](https://github.com/CQCL/tket2/compare) if you have any questions or suggestions.

justfile

@@ -29,4 +29,12 @@ check:
 # Format the code
 format:
     cargo fmt
-    ruff format .
+    ruff format .
+
+# Generate a test coverage report
+coverage:
+    cargo llvm-cov --lcov > lcov.info
+
+# Generate a python test coverage report
+pycoverage: pydevelop
+    pytest --cov=./ --cov-report=html

pyproject.toml

@@ -18,6 +18,7 @@ python = ">=3.10"
 maturin = "^1.3.0"
 pytket = "*"
 pytest = "^7.1.2"
+pytest-cov = "^4.1.0"
 ruff = "^0.1.3"
 
 [build-system]