catch2/examples/302-Gen-Table.cpp

// 302-Gen-Table.cpp
// Shows how to use table to run a test many times with different inputs. Lifted from examples on
// issue #850.

#include <catch2/catch_test_macros.hpp>
#include <catch2/generators/catch_generators.hpp>
#include <string>

struct TestSubject {
    // this is the method we are going to test. It returns the length of the
    // input string.
    size_t GetLength( const std::string& input ) const { return input.size(); }
};


TEST_CASE("Table allows pre-computed test inputs and outputs", "[example][generator]") {
    using std::make_tuple;
    // do setup here as normal
    TestSubject subj;

    SECTION("This section is run for each row in the table") {
        std::string test_input;
        size_t expected_output;
        std::tie( test_input, expected_output ) =
            GENERATE( table<std::string, size_t>(
                { /* In this case one of the parameters to our test case is the
                   * expected output, but this is not required. There could be
                   * multiple expected values in the table, which can have any
                   * (fixed) number of columns.
                   */
                  make_tuple( "one", 3 ),
                  make_tuple( "two", 3 ),
                  make_tuple( "three", 5 ),
                  make_tuple( "four", 4 ) } ) );

        // run the test
        auto result = subj.GetLength(test_input);
        // capture the input data to go with the outputs.
        CAPTURE(test_input);
        // check it matches the pre-calculated data
        REQUIRE(result == expected_output);
    }   // end section
}

/* Possible simplifications where less legacy toolchain support is needed:
 *
 * - With libstdc++6 or newer, the make_tuple() calls can be omitted
 * (technically C++17 but does not require -std in GCC/Clang). See
 *   https://stackoverflow.com/questions/12436586/tuple-vector-and-initializer-list
 *
 * - In C++17 mode std::tie() and the preceding variable declarations can be
 * replaced by structured bindings: auto [test_input, expected] = GENERATE(
 * table<std::string, size_t>({ ...
 */
// Compiling and running this file will result in 4 successful assertions