How I can get coverage for cargo test?

Question

When I want to test C++ coverage, I can build my program with -fprofile-arcs -ftest-coverage, run all tests, and run gcov to get coverages.

However, when it comes to Rust, I get totally lost. What I want to do is run the following tests(on my Mac), and get coverage of all Rust codes in path components/raftstore

cargo test --package tests --test failpoints cases::test_normal
cargo test --package tests --test failpoints cases::test_bootstrap
cargo test --package tests --test failpoints cases::test_compact_log

From this post, it says firstly run cargo test --no-run, then run kcov. However, when I actually do that, kcov blocks forever.

Then I find something called cargo kcov, who provides --test. However when I run cargo kcov --test failpoints cases::test_normal like what I do in cargo test, I get error

error: cargo subcommand failure
note: cargo test exited with code exit status: 101
error: no test target named `failpoints`

I have tried many ways to figure this out, however, none of them works, so I wonder if I can get some help here.

I know there are other coverage tools like tarpaulin and grcov, I am currently trying those. It is also acceptable if there are neat solutions with those coverage tools. However, I still want to know what is wrong with kcov and cargo-kcov.

Thanks for pointing it out @Astariul. Please refer to the answer below which I've just posted. It also contains the link the corresponding section in the rustc book. — mori, Nov 04 '22 at 12:17

score 4 · Answer 1 · answered Mar 20 '23 at 15:38

4

I like to use tarpaulin with the HTML output.

cargo tarpaulin --out Html

This should create an output file named tarpaulin-report.html. Open this file in the browser to view the code coverage report.

answered Mar 20 '23 at 15:38

Jim

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mori · Answer 2 · 2022-11-04T15:15:23.473

According to rustc docs, it's now possible to obtain instrumentation-based code coverage.

The following command generates coverage results. Note that it requires the Rust profiler runtime, which is included by default in nightly.

RUSTFLAGS="-C instrument-coverage" \
    cargo test --tests

These results may include mangled symbol names, which can be worked around with rustfilt:

cargo install rustfilt

After running tests with this setup there should be one or more .profraw files. If there are multiple, they can be merged with:

$ llvm-profdata merge -sparse default_*.profraw -o your_crate.profdata

Coverage information can then be shown with llvm-cov, for instance like described in this section (substitute the names of your crate and test binaries).

There might be issues if the LLVM versions of rustc and llvm-profdata resp. llvm-cov don't match, as noted here.

This answer is based on this section of the rustc book, which offers much more information on code coverage.

Saurabh · Answer 3 · 2023-04-30T01:28:57.680

You can generate source-based coverage for your project by:

Enable coverage profile in Cargo.toml:
```
...
[build]
profiler = true
...
```
Install demangler
```
cargo install rustfilt
```

Add instrument coverage

export RUSTFLAGS="-C instrument-coverage=all"

Install dependencies openssl-devel, libssl-devel, llvm, and genhtml, based on your OS
Install Mozilla's grcov and link the profiler with the rust compiler
```
cargo install grcov
rustup component add llvm-tools-preview
```
Run tests
```
cargo test --verbose
```

Generate code coverage information

grcov . -s . --binary-path ./target/debug/ -t lcov --branch --ignore-not-existing -o ./target/debug/

Create HTML report from coverage data

genhtml -o ./target/debug/coverage/ --show-details --highlight --ignore-errors source --legend ./target/debug/lcov

And finally view the HTML report at ./target/debug/coverage/index.html

How I can get coverage for cargo test?

3 Answers3