What it is
Catch2 is a modern, header-only C++ unit testing framework. It provides a simple syntax for writing test cases and assertions, making it easy to write, maintain, and execute tests for C++ projects.
Catch2 allows defining test cases with `TEST_CASE` macros and verifying conditions using `REQUIRE`, `CHECK`, and related assertions. It supports sections, tags, BDD-style tests, and integration with build systems for automated testing.
- Licence
- Boost Software License
- Watch for
- Catch2 v3 is compiled rather than header-only, which speeds builds
When to use it
The question documentation cannot answer for you — because it cannot recommend something else.
Reach for it when
- You want tests running with minimal build setup
- BDD-style sections and readable assertion output matter to the team
Look elsewhere when
- You need extensive mocking — GoogleTest with GoogleMock is stronger there
Installation
sudo apt install catch2Getting started
The smallest useful thing you can do with it, and what each part means.
#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>
TEST_CASE("Factorials are computed correctly", "[factorial]") {
REQUIRE( Factorial(0) == 1 );
REQUIRE( Factorial(1) == 1 );
REQUIRE( Factorial(2) == 2 );
REQUIRE( Factorial(3) == 6 );
}TEST_CASE("Vectors can be sized and resized", "[vector]") {
std::vector<int> v(5);
CHECK( v.size() == 5 );
v.push_back(1);
CHECK( v.size() == 6 );
}Advanced usage
Where the library earns its place over a simpler alternative.
TEST_CASE("Testing different scenarios") {
SECTION("Empty vector") {
std::vector<int> v;
REQUIRE(v.empty());
}
SECTION("Non-empty vector") {
std::vector<int> v = {1,2,3};
REQUIRE(v.size() == 3);
}
}TEST_CASE("String manipulation", "[string][manipulation]") {
REQUIRE( toUpper("abc") == "ABC" );
}SCENARIO("Vectors can be resized") {
GIVEN("A vector with 3 elements") {
std::vector<int> v = {1,2,3};
WHEN("an element is added") {
v.push_back(4);
THEN("the size increases") {
REQUIRE(v.size() == 4);
}
}
}
}Errors and fixes
The failures you are most likely to hit, and what actually resolves them.
- Assertion failure
- Catch2 will report failed assertions with line numbers and messages. Review the test case logic and input data.
- Test case not executed
- Ensure that `TEST_CASE` macros are correctly defined and that the test file is compiled with Catch2.
Best practices
- Use `REQUIRE` for critical assertions and `CHECK` for non-fatal checks.
- Organize tests with tags for selective execution.
- Use sections to reduce code duplication for similar test scenarios.
- Keep test cases small and focused on a single functionality.
- Integrate Catch2 tests with CI pipelines for automated testing.
Alternatives
Comparable options, and the reason you would pick one over the other.
GoogleTest
Richer feature set including GoogleMock; heavier setup
doctest
Similar style with much faster compilation
Background
Why it exists, and what it was reacting to.
Catch2 was created by Phil Nash as the successor to the original Catch framework. Its goal is to simplify unit testing in C++ by providing expressive macros, automatic test registration, and rich reporting while being lightweight and easy to integrate.