1. Test Discovery Fails

Understanding the Issue

Some or all tests are not detected or executed when running Catch2 tests.

Root Causes

• Incorrect test macros or missing test cases.
• Tests filtered out due to command-line options.
• Multiple translation units with separate Catch2 instances.

Fix

Ensure correct test case macros are used:

TEST_CASE("Example test") {
    REQUIRE(1 + 1 == 2);
}

Run tests without filters to verify discovery:

./tests --list-tests

Ensure all test definitions are in a single translation unit:

#define CATCH_CONFIG_MAIN
#include "catch2/catch.hpp"

2. Linker Errors

Understanding the Issue

Compilation succeeds, but linking fails with errors like undefined reference to Catch::Session.

Root Causes

• Catch2 is missing from the build system.
• Test definitions exist in multiple translation units.
• Incorrect Catch2 version mismatching test cases.

Fix

Ensure Catch2 is properly linked:

g++ -std=c++17 tests.cpp -o tests -I/path/to/catch2

Use CATCH_CONFIG_MAIN only in one file:

#define CATCH_CONFIG_MAIN
#include "catch2/catch.hpp"

Check installed Catch2 version:

apt list --installed | grep catch2

3. Incorrect Assertion Results

Understanding the Issue

Assertions in test cases do not behave as expected, leading to false positives or negatives.

Root Causes

• Incorrect assertion macros used.
• Floating-point precision issues.
• Incorrect variable scopes or mutations during tests.

Fix

Use the correct assertion macros:

REQUIRE( value == expected );

For floating-point comparisons, use Approx:

REQUIRE( result == Approx(expected).epsilon(0.01) );

Ensure variables are not modified unexpectedly:

const int result = functionUnderTest();
REQUIRE( result == expected );

4. Performance Issues in Large Test Suites

Understanding the Issue

Running Catch2 tests takes longer than expected, affecting development workflows.

Root Causes

• Excessive logging in test cases.
• Large number of test cases running in a single execution.
• Expensive setup/teardown operations.

Fix

Run only failed tests to save time:

./tests --last-failed

Use BENCHMARK for performance-critical tests:

TEST_CASE("Performance Test") {
    BENCHMARK("Sorting large array") {
        std::sort(data.begin(), data.end());
    };
}

Reduce logging for better performance:

./tests -d no

5. Catch2 Integration Issues with CMake

Understanding the Issue

Catch2 does not integrate properly with CMake-based projects, leading to build failures.

Root Causes

• Catch2 is not installed or not found by CMake.
• Incorrect CMake configuration for header-only Catch2.
• Multiple conflicting versions of Catch2 in the project.

Fix

Ensure Catch2 is installed via package manager:

sudo apt install catch2

Use FetchContent in CMake to include Catch2:

include(FetchContent)
FetchContent_Declare(
    Catch2
    GIT_REPOSITORY https://github.com/catchorg/Catch2.git
    GIT_TAG v2.13.7
)
FetchContent_MakeAvailable(Catch2)

Link Catch2 correctly in CMake:

target_link_libraries(my_tests PRIVATE Catch2::Catch2)

Conclusion

Catch2 is a versatile C++ testing framework, but troubleshooting test discovery issues, linker errors, incorrect assertions, performance bottlenecks, and CMake integration problems is essential for smooth development. By properly configuring the build environment, optimizing test execution, and refining assertion usage, developers can leverage Catch2 efficiently.

FAQs

1. Why is Catch2 not discovering my tests?

Ensure correct test macros are used, avoid multiple translation units, and check command-line filters.

2. How do I fix Catch2 linker errors?

Ensure Catch2 is properly linked, include only one CATCH_CONFIG_MAIN, and verify installation paths.

3. Why are my assertions in Catch2 giving incorrect results?

Use the correct macros, handle floating-point precision properly, and prevent unintended variable modifications.

4. How can I speed up Catch2 test execution?

Run only failed tests, use benchmarking, and reduce excessive logging.

5. How do I integrate Catch2 with CMake?

Use FetchContent to download Catch2 and link it properly in CMake configurations.