Add an example of using GENERATE(table())

There are some examples on issue #850 of using this feature, but they
are not easily found from the documentation. Adding them here as an
example makes them more findable and ensures they keep working if the
API changes.
This commit is contained in:
Richard Ash 2020-06-19 15:32:08 +01:00 committed by Martin Hořeňovský
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commit 2840ce1e70
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@ -14,6 +14,7 @@
- Configuration: [Provide your own output streams](../examples/231-Cfg-OutputStreams.cpp) - Configuration: [Provide your own output streams](../examples/231-Cfg-OutputStreams.cpp)
- Generators: [Create your own generator](../examples/300-Gen-OwnGenerator.cpp) - Generators: [Create your own generator](../examples/300-Gen-OwnGenerator.cpp)
- Generators: [Use map to convert types in GENERATE expression](../examples/301-Gen-MapTypeConversion.cpp) - Generators: [Use map to convert types in GENERATE expression](../examples/301-Gen-MapTypeConversion.cpp)
- Generators: [Run test with a table of input values](../examples/302-Gen-Table.cpp)
- Generators: [Use variables in generator expressions](../examples/310-Gen-VariablesInGenerators.cpp) - Generators: [Use variables in generator expressions](../examples/310-Gen-VariablesInGenerators.cpp)
- Generators: [Use custom variable capture in generator expressions](../examples/311-Gen-CustomCapture.cpp) - Generators: [Use custom variable capture in generator expressions](../examples/311-Gen-CustomCapture.cpp)

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@ -0,0 +1,55 @@
// 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 ommitted
* (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 preceeding variable delcarations 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

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@ -32,6 +32,7 @@ set( SOURCES_IDIOMATIC_EXAMPLES
210-Evt-EventListeners.cpp 210-Evt-EventListeners.cpp
300-Gen-OwnGenerator.cpp 300-Gen-OwnGenerator.cpp
301-Gen-MapTypeConversion.cpp 301-Gen-MapTypeConversion.cpp
302-Gen-Table.cpp
310-Gen-VariablesInGenerators.cpp 310-Gen-VariablesInGenerators.cpp
311-Gen-CustomCapture.cpp 311-Gen-CustomCapture.cpp
) )