Open code review: Catch
This is one of the “open code review” posts, where I publish my notes after looking through and playing with one of the open source C++ projects. My main goal here is to become a better coder by learning from the experience of other developers, and my secondary goal is to build a mental map of the tools and frameworks available “out there” to not reinvent the proverbial wheel, should I ever need one. The blog post expresses my personal opinion, not affiliated, endorsed, sponsored, etc. I am not arguing for or against the usage of any specific open source library. I will be grateful if you take time to point out any misunderstanding I might have.
Today I looked at philsquared/Catch, “a multi-paradigm automated test framework for C++ and Objective-C (and, maybe, C)”.
Actually, it was long on my list of “to-read” projects, since the first time I’ve heard of it was at the “Meeting C++” conference in December ’14, where Phil Nash, its author, talked about it.
So, why bother about this “yet another” test framework? Catch dedicates a page to the answer, but here’s what caught my attention:
- extreme simplicity and minimalism of the design (you need to learn very few things to start writing Catch tests);
- plain text snippets as “first-class” citizens in test names and descriptions (so the tests look like a spec, and test assertions give richer description of the failed requirement);
- an inventive way to get rid of setup code duplication via the mechanism of “sections” (saves you some coding, see below an example of how sections work).
Here’s how a trivial test in Catch looks like, from its tutorial:
#define CATCH_CONFIG_MAIN // This tells Catch to provide a main() - only do this in one cpp file
#include "catch.hpp"
unsigned int Factorial(unsigned int number) {
return number <= 1 ? number : Factorial(number - 1)*number;
}
TEST_CASE("Factorials are computed", "[factorial]") {
REQUIRE(Factorial(1) == 1);
REQUIRE(Factorial(2) == 2);
REQUIRE(Factorial(3) == 6);
REQUIRE(Factorial(10) == 3628800);
}
And here’s my somewhat unorthodox demo of Catch “sections”. I’m trying to illustrate the mechanism of the section tree traversal. This is not a test at all, I’m using Catch sections here to print 4 lines from Shakespeare which share some of their first few words starting with “Thou shalt…” :) For a more practical example see the vector tests in the Catch tutorial.
#define CATCH_CONFIG_MAIN
#include "catch.hpp"
#include <iostream>
#include <string>
using namespace std;
// Catch "sections" are "forks" in the test execution tree.
// A test run traverses all possible paths to the leaves.
// This test case produces 4 strings by traversing 4 paths.
TEST_CASE("4 lines from Shakespeare")
{
cout << "Thou shalt "; // http://www.rhymezone.com/r/ss.cgi?q=thou+shalt
SECTION("...not")
{
cout << "not ";
SECTION("")
cout << "stir a foot to seek a foe. (Romeo and Juliet: I, i)" << endl;
SECTION("")
cout << "sigh, nor hold thy stumps to heaven, (Titus Andronicus: III, ii)" << endl;
}
SECTION("")
cout << "remain here, whether thou wilt or no. (A Midsummer Night's Dream: III, i)" << endl;
SECTION("")
cout << "continue two and forty hours, (Romeo and Juliet: IV, i)" << endl;
}
// Test output:
//Thou shalt not stir a foot to seek a foe. (Romeo and Juliet: I, i)
//Thou shalt not sigh, nor hold thy stumps to heaven, (Titus Andronicus: III, ii)
//Thou shalt remain here, whether thou wilt or no. (A Midsummer Night's Dream: III, i)
//Thou shalt continue two and forty hours, (Romeo and Juliet: IV, i)
//===============================================================================
//test cases: 1 | 1 passed
//assertions: - none -