Testing

This document provides an outline of different kinds of tests used by the cxx project.

Errors from proc macro

We want to verify that the #[cxx::bridge] macro reports expected error messages when invoked by rustc on certain inputs.

Such verification is handled by test cases underneath tests/ui directory and driven by tests/compiletest.rs. The test cases consist of a pair of files:

• foo.rs is the input
• foo.stderr is the expected Rust compiler diagnostic

Errors from C++ compiler

We want to verify that cxx's generated C++ code triggers expected C++ compiler diagnostics on certain inputs.

Such verification is covered by tests/cpp_ui_tests.rs.

End-to-end functionality

End-to-end functional tests are structured as follows:

• The code under test is contained underneath tests/ffi directory which contains:
  • Rust code under test &emdash; the cxx-test-suite crate (lib.rs and module.rs) with:
    • A few #[cxx::bridge] invocations
    • Rust types (e.g. struct R)
    • Rust functions and methods (e.g. fn r_return_primitive)
  • C/C++ code under test (tests.h and tests.cc)
    • C++ types (e.g. class C)
    • C++ functions and methods (e.g. c_return_primitive)
• The testcases can be found in:
  • Rust calling into C++: tests/test.rs.
  • C++ calling into Rust: tests/ffi/test.cc. These tests are manually dispatched from the cxx_run_test function in tests/ffi/test.cc.