Catch2 now uses statically compiled library as its distribution model. This also means that to get all of Catch2's functionality in a test file, you have to include multiple headers.

You probably want to look into the migration docs, which were written to help people coming from v2.x.x versions to the v3 releases.

FAQ

• Why is Catch2 moving to separate headers?
  • The short answer is future extensibility and scalability. The long answer is complex and can be found on my blog, but at the most basic level, it is that providing single-header distribution is at odds with providing variety of useful features. When Catch2 was distributed in a single header, adding a new Matcher would cause overhead for everyone, but was useful only to a subset of users. This meant that the barrier to entry for new Matchers/Generators/etc is high in single header model, but much smaller in the new model.
• Will Catch2 again distribute single-header version in the future?
  • No. But we do provide sqlite-style amalgamated distribution option. This means that you can download just 1 .cpp file and 1 header and place them next to your own sources. However, doing this has downsides similar to using the catch_all.hpp header.
• Why the big breaking change caused by replacing catch.hpp with catch_all.hpp?
  • The convenience header catch_all.hpp exists for two reasons. One of them is to provide a way for quick migration from Catch2, the second one is to provide a simple way to test things with Catch2. Using it for migration has one drawback in that it is big. This means that including it will cause significant compile time drag, and so using it to migrate should be a conscious decision by the user, not something they can just stumble into unknowingly.

(Potentially) Breaking changes

• Catch2 now uses statically compiled library as its distribution model
  • Including catch.hpp no longer works
• Catch2 now uses C++14 as the minimum support language version
• ANON_TEST_CASE has been removed, use TEST_CASE with no arguments instead (#1220)
• --list* commands no longer have non-zero return code (#1410)
• --list-test-names-only has been removed (#1190)
  • You should use verbosity-modifiers for --list-tests instead
• --list* commands are now piped through the reporters
  • The top-level reporter interface provides default implementation that works just as the old one
  • XmlReporter outputs a machine-parseable XML
• TEST_CASE description support has been removed
  • If the second argument has text outside tags, the text will be ignored.
• Hidden test cases are no longer included just because they don't match an exclusion tag
  • Previously, a TEST_CASE("A", "[.foo]") would be included by asking for ~[bar].
• PredicateMatcher is no longer type erased.
  • This means that the type of the provided predicate is part of the PredicateMatcher's type
• SectionInfo no longer contains section description as a member (#1319)
  • You can still write SECTION("ShortName", "Long and wordy description"), but the description is thrown away
  • The description type now must be a const char* or be implicitly convertible to it
• The [!hide] tag has been removed.
  • Use [.] or [.foo] instead.
• Lvalues of composed matchers cannot be composed further
• Uses of REGISTER_TEST_CASE macro need to be followed by a semicolon
  • This does not change TEST_CASE and friends in any way
• IStreamingReporter::IsMulti member function was removed
  • This is very unlikely to actually affect anyone, as it was default-implemented in the interface, and only used internally
• Various classes not designed for user-extension have been made final
  • ListeningReporter is now final
  • Concrete Matchers (e.g. UnorderedEquals vector matcher) are now final
  • All Generators are now final
• Matcher namespacing has been redone
  • Matcher types are no longer in deeply nested namespaces
  • Matcher factory functions are no longer brought into Catch namespace
  • This means that all public-facing matcher-related functionality is now in Catch::Matchers namespace
• Defining CATCH_CONFIG_MAIN will no longer create main in that TU.
  • Link with libCatch2Main.a, or the proper CMake/pkg-config target
  • If you want to write custom main, include catch2/catch_session.hpp
• CATCH_CONFIG_EXTERNAL_INTERFACES has been removed.
  • You should instead include the appropriate headers as needed.
• CATCH_CONFIG_IMPL has been removed.
  • The implementation is now compiled into a static library.
• Event Listener interface has changed
  • TestEventListenerBase was renamed to EventListenerBase
  • EventListenerBase now directly derives from IStreamingReporter, instead of deriving from StreamingReporterBase
• GENERATE decays its arguments (#2012, #2040)
  • This means that str in auto str = GENERATE("aa", "bb", "cc"); is inferred to char const* rather than const char[2].
• --list-* flags write their output to file specified by the -o flag
• Many changes to reporter interfaces
  • With the exception of the XmlReporter, the outputs of first party reporters should remain the same
  • New pair of events were added
  • One obsolete event was removed
  • The base class has been renamed
  • The built-in reporter class hierarchy has been redone
• Catch2 generates a random seed if one hasn't been specified by the user
• The short flag for --list-tests, -l, has been removed.
  • This is not a commonly used flag and does not need to use up valuable single-letter space.
• The short flag for --list-tags, -t, has been removed.
  • This is not a commonly used flag and does not need to use up valuable single-letter space.
• The --colour option has been replaced with --colour-mode option

Improvements

• Matchers have been extended with the ability to use different signatures of match (#1307, #1553, #1554, #1843)
  • This includes having templated match member function
  • See the rewritten Matchers documentation for details
  • Catch2 currently provides some generic matchers, but there should be more before final release of v3
    • IsEmpty, SizeIs which check that the range has specific properties
    • Contains, which checks whether a range contains a specific element
    • AllMatch, AnyMatch, NoneMatch range matchers, which apply matchers over a range of elements
• Significant compilation time improvements
  • including catch_test_macros.hpp is 80% cheaper than including catch.hpp
• Some runtime performance optimizations
  • In all tested cases the v3 branch was faster, so the table below shows the speedup of v3 to v2 at the same task

• POSIX platforms use gmtime_r, rather than gmtime when constructing a date string (#2008, #2165)
• --list-* flags write their output to file specified by the -o flag (#2061, #2163)
• Approx::operator() is now properly const
• Catch2's internal helper variables no longer use reserved identifiers (#578)
• --rng-seed now accepts string "random-device" to generate random seed using std::random_device
• Catch2 now supports test sharding (#2257)
  • You can ask for the tests to be split into N groups and only run one of them.
  • This greatly simplifies parallelization of tests in a binary through external runner.
• The embedded CLI parser now supports repeatedly callable lambdas
  • A lambda-based option parser can opt into being repeatedly specifiable.
• Added STATIC_CHECK macro, similar to STATIC_REQUIRE (#2318)
  • When deferred tu runtime, it behaves like CHECK, and not like REQUIRE.
• You can have multiple tests with the same name, as long as other parts of the test identity differ (#1915, #1999, #2175)
  • Test identity includes test's name, test's tags and and test's class name if applicable.
• Added new warning, UnmatchedTestSpec, to error on test specs with no matching tests
• The -w, --warn warning flags can now be provided multiple times to enable multiple warnings
• The case-insensitive handling of tags is now more reliable and takes up less memory
• Test case and assertion counting can no longer reasonably overflow on 32 bit systems
  • The count is now kept in uint64_t on all platforms, instead of using size_t type.
• The -o, --out output destination specifiers recognize - as stdout
  • You have to provide it as --out=- to avoid CLI error about missing option
  • The new reporter specification also recognizes - as stdout
• Multiple reporters can now run at the same time and write to different files (#1712, #2183)
  • To support this, the -r, --reporter flag now also accepts optional output destination
  • For full overview of the semantics of using multiple reporters, look into the reporter documentation
  • To enable the new syntax, reporter names can no longer contain ::.
• Console colour support has been rewritten and significantly improved
  • The colour implementation based on ANSI colour codes is always available
  • Colour implementations respect their associated stream
    • previously e.g. Win32 impl would change console colour even if Catch2 was writing to a file
  • The colour API is resilient against changing evaluation order of expressions
  • The associated CLI flag and compile-time configuration options have changed
    • For details see the docs for command-line and compile-time Catch2 configuration
• Added a support for Bazel integration with XML_OUTPUT_FILE env var (#2399)
  • This has to be enabled during compilation.
• Added --skip-benchmarks flag to run tests without any BENCHMARKs (#2392, #2408)
• Added option to list all listeners in the binary via --list-listeners

Fixes

• The INFO macro no longer contains superfluous semicolon (#1456)
• The --list* family of command line flags now return 0 on success (#1410, #1146)
• Various ways of failing a benchmark are now counted and reporter properly
• The ULP matcher now handles comparing numbers with different signs properly (#2152)
• Universal ADL-found operators should no longer break decomposition (#2121)
• Reporter selection is properly case-insensitive
  • Previously it forced lower cased name, which would fail for reporters with upper case characters in name
• The cumulative reporter base stores benchmark results alongside assertion results
• Catch2's SE handling should no longer interferes with ASan on Windows (#2334)
• Fixed Windows console colour handling for tests that redirect stdout (#2345)
• Fixed issue with the random generators returning the same value over and over again

Other changes

• CATCH_CONFIG_DISABLE_MATCHERS no longer exists.
  • If you do not want to use Matchers in a TU, do not include their header.
• CATCH_CONFIG_ENABLE_CHRONO_STRINGMAKER no longer exists.
  • StringMaker specializations for <chrono> are always provided
• Catch2's CMake now provides 2 targets, Catch2 and Catch2WithMain.
  • Catch2 is the statically compiled implementation by itself
  • Catch2WithMain also links in the default main
• Catch2's pkg-config integration also provides 2 packages
  • catch2 is the statically compiled implementation by itself
  • catch2-with-main also links in the default main
• Passing invalid test specifications passed to Catch2 are now reported before tests are run, and are a hard error.
• Running 0 tests (e.g. due to empty binary, or test spec not matching anything) returns non-0 exit code
  • Flag --allow-running-no-tests overrides this behaviour.
  • NoTests warning has been removed because it is fully subsumed by this change.
• Catch2's compile-time configuration options (CATCH_CONFIG_FOO) can be set through CMake options of the same name
  • They use the same semantics as C++ defines, including the CATCH_CONFIG_NO_FOO overrides,
    • -DCATCH_CONFIG_DEFAULT_REPORTER=compact changes default reporter to "compact"
    • -DCATCH_CONFIG_NO_ANDROID_LOGWRITE=ON forces android logwrite to off
    • -DCATCH_CONFIG_ANDROID_LOGWRITE=OFF does nothing (the define will not exist)