catch2/docs/migrate-v2-to-v3.md

Migrating from v2 to v3

If you want to migrate to v3, there are two basic approaches to do so.

1. Use catch_amalgamated.hpp and catch_amalgamated.cpp.
2. Build Catch2 as a proper (static) library, and move to piecewise headers

Doing 1 means downloading the amalgamated header and the amalgamated sources from extras, dropping them into your test project, and rewriting your includes from <catch2/catch.hpp> to "catch_amalgamated.hpp" (or something similar, based on how you set up your paths).

The disadvantage of using this approach are increased compilation times, at least compared to the second approach, but it does let you avoid dealing with consuming libraries in your build system of choice.

However, we recommend doing 2, and taking extra time to migrate to v3 properly. This lets you reap the benefits of significantly improved compilation times in the v3 version. The basic steps to do se are:

1. Change your CMakeLists.txt to link against Catch2WithMain target if you use Catch2's default main. (If you do not, keep linking against the Catch2 target.)
2. Delete TU with CATCH_CONFIG_RUNNER or CATCH_CONFIG_MAIN defined, as it is no longer needed.
3. Change #include <catch2/catch.hpp> to #include <catch2/catch_all.hpp>
4. Check that everything compiles. You might have to modify namespaces, or perform some other changes (see the Things that can break during porting section for the most common things).
5. Start migrating your test TUs from including <catch2/catch_all.hpp> to piecemeal includes. You will likely want to start by including <catch2/catch_test_macros.hpp>, and then go from there. (see other notes for further ideas)

Other notes

• The main test include is now <catch2/catch_test_macros.hpp>
• Big "subparts" like Matchers, or Generators, have their own folder, and also their own "big header", so if you just want to include all matchers, you can include <catch2/matchers/catch_matchers_all.hpp>, or <catch2/generators/catch_generators_all.hpp>

Things that can break during porting

• The namespace on Matchers were cleaned up, they are no longer first declared deep within an internal namespace and then brought up. All Matchers now live in Catch::Matchers.
• The reporter interfaces changed in a breaking manner. If you wrote custom reporter or listener, you might need to modify them a bit.

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