Getting started with unit tests in Qt Creator and Catch

I have written about unit testing in Qt Creator on multiple occasions earlier. Since then, a new testing framework seems to have become a new leader in the field, and that is Catch. It is similar to UnitTest++ and Google’s gtest and brings the best of both worlds. It is header-only and appears to reduce the amount of code that must be written in comparison to the other two.

This is an adopted version my previous posts that shows how to use Catch in a Qt Creator project. It doesn’t any longer integrate the testing output into Qt Creator’s issue pane. Instead I’ve started to rely on Travis CI or Jenkins to run the tests and notify me about any newly introduced errors.

An example project using this code structure has been posted on Github by Filip Sund (thanks, Filip!) and further adapted by us with the move to Catch.

The structure of the project is as follows:

MyProject
├─ MyProject.pro
├─ defaults.pri
├─ app/
│  ├─ app.pro
│  └─ main.cpp
├─ src/
│  ├─ src.pro
│  └─ myclass.cpp
└─ tests/
   ├─ tests.pro
   └─ main.cpp

The main project file, MyProject.pro will now be based on a subdirs template, and may look like this:

TEMPLATE = subdirs
CONFIG+=ordered
SUBDIRS = \
    src \
    app \
    tests
app.depends = src
tests.depends = src

The app.depends and tests.depends statements makes sure that the src project is compiled before the application and tests. This is because the src directory contains the library that will be used by both the app and the tests.

CONFIG+=ordered is needed because depends doesn’t affect the order during make install.

defaults.pri

Each of the other .pro files will include defaults.pri to have all the headers available. defaults.pri contains the following:

INCLUDEPATH += $$PWD/src
SRC_DIR = $$PWD

If the library, main program and tests use common libraries, it is very useful to have the defaults.pri define these dependencies too.

./src

In the src folder, I have myclass.cpp, which is the class that I want to use and test. The src.pro needs to compile to a library, so that it may be used both by app and tests, and could look something like this:

include(../defaults.pri)
CONFIG -= qt

TARGET = myapp
TEMPLATE = lib

SOURCES += myclass.cpp
HEADERS += myclass.h

What this class does is not so interesting, it could be anything. A simple example could be this header file:

#ifndef MYCLASS_H
#define MYCLASS_H

class MyClass {
public:
    double addition(double a, double b);
};

#endif // MYCLASS_H

With this accompaning source file:

#include "myclass.h"

double MyClass::addition(double a, double b) {
    return a * b;
}

./app

I only have a main.cpp file in app, because the app is basically just something that uses everything in the src folder. It will depend on the shared compiled library from src, and app.pro would look something like this:

include(../defaults.pri)

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += main.cpp

LIBS += -L../src -lmyapp

The main.cpp file could be a simple program that uses MyClass:

#include <myclass.h>
#include <iostream>

using namespace std;

int main()
{
    MyClass adder;
    cout << adder.addition(10, 20) << endl;
    return 0;
}

./tests

In the tests folder I have simply added a main.cpp which will run the tests. Then tests.pro has the following contents:

include(../defaults.pri)
TEMPLATE = app

CONFIG   += console
CONFIG   -= app_bundle
CONFIG   -= qt

SOURCES += main.cpp

LIBS += -L../src -lmyapp

Which now links to the myapp library in addition to the unit tests.

The main.cpp in tests file which could contain the following, if we were to use UnitTest++ as our testing library:

#define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
#include "catch.hpp"
#include <myclass.h>

TEST_CASE( "MyMath", "[mymath]" ) {
    SECTION("Addition") {
        MyClass my;
        REQUIRE(my.addition(3,4) == 7);
    }
}

This test will fail because my implementation of MyClass::addition is completely wrong:

class MyClass {
public:
    double addition(double a, double b) {
        return a * b;
    }
};

Note that I’m including MyClass by through <myclass.h> which is possible because of the INCLUDEPATH variable in defaults.pri.

This should help you define a project that compiles a library, as well as tests and an application using the library.

Published by

Svenn-Arne Dragly

I'm a physicist and programmer, writing about the stuff I figure out as I go.

3 thoughts on “Getting started with unit tests in Qt Creator and Catch”

  1. Thank you very much! Exactly what I was searching for…

    Though I have noticed a mistake in your tutorial. You write LIBS += -L../src -lmyapp, but Qt places the .dll file to the debug folder, so it would be right to set LIBS += -L../src/debug -lmyapp. I am not sure that this is not my project’s personal issue, maybe it all depends on the build settings I have.

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