Unit Testing with multiple .cpp files

ATE-ENGE · 2 May 2025, 14:43

Hello all,

I'm new to programming / QT and am trying to implement unit tests for my application. The application will have multiple classes and I would like to write unit tests to pair with these classes as well as the project as a whole. Looking at the forums and GPT example code, I understand I should have my project built like so:

Project.pro
Headers
--mainwindow.h
--src/
----class1.h
----class2.h
Sources
--mainwindow.cpp
--main.cpp
--src/
----class1.h
----class2.h
Forms
--mainwindow.ui
Other files
--tests/
----tst_class1
----tst_class2
----tst_class1and2

With my .pro file containing:

QT       += core gui testlib
CONFIG += c++17 testcase
SOURCES += \
    main.cpp \
    mainwindow.cpp \
    src/class1.cpp \
    src/class2.cpp \

HEADERS += \
    mainwindow.h \
    src/class1.h \
    src/class2.h \

FORMS += \
    mainwindow.ui

# Test sources
test1.sources = tests/tst_class1.cpp
test1.target = tst_class1
test1.CONFIG += console
test1.CONFIG += testcase

test2.sources = tests/tst_class2.cpp
test2.target = tst_class2
test2.CONFIG += console
test2.CONFIG += testcase

test3.sources = tests/tst_class1and2.cpp
test3.target = tst_class1and2
test3.CONFIG += console
test3.CONFIG += testcase

# Include the test sources in the project
OTHER_FILES += \
    tests/tst_class1.cpp \
    tests/tst_class2.cpp \
    tests/tst_class1and2.cpp

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

DISTFILES +=

I have each tst file containing

#include <QtTest>
#include "src/class1.h"

class TestStateMachine : public QObject {
    Q_OBJECT

private slots:
    void initTestCase();
    void test1A();
    void test1B();
    void cleanupTestCase();
};

[function definitions here]

QTEST_MAIN(TestStateMachine)
#include "tst_main.moc"

If possible there are two things I'd like to fix.

Most important although the program compiles, I understand that I'm supposed to see tst_class1.exe in my build folder and I do not, so I have no idea if the tests are being run or how to run them
I know QT has the display window "8 Test Results," with output that the provided example uses. Looking at help documents from ~2019, it looks like this won't populate if you have multiple test files (or the only way to have multiple test files subverts this window.) Is that still the case?

SGaist · 5 Feb 2025, 19:04

Hi,

That is usually done using the SUBDIRS template where each test is its own project as is the application.

Often you will have a library project that contains your application business logic and that will also contain the tests and an app project that will make use of the library.

ATE-ENGE · 2 May 2025, 19:04

@SGaist Fantastic! Thank you for letting me know. I'm looking at the wiki here (https://wiki.qt.io/SUBDIRS_-_handling_dependencies) and seeing the example:

/FooApp
   |--- Makefile
   |--- subdirs.pro
   |--- src
        |
        |--- app
        |    |--- app.pro
        |    |--- Makefile
        |    |--- Makefile.Debug
        |    |--- Makefile.Release
        |    `--- ... (source files of app)
        |--- lib
        |    |--- lib.pro
        |    |--- Makefile
        |    |--- Makefile.Debug
        |    |--- Makefile.Release
        |    `--- ... (source files of lib)
        |--- lib2
        |    |--- lib2.pro
        |    |--- Makefile
        |    |--- Makefile.Debug
        |    |--- Makefile.Release

For my project, would that then translate to?

/FooApp
   |--- Makefile
   |--- subdirs.pro
   |--- src
        |
        |--- app
        |    |--- app.pro
        |    |--- mainwindow.h 
        |    |--- mainwindow.cpp        
        |    |--- main.cpp
        |    |--- tst_class1and2
        |--- class 1
        |    |--- class1.pro
        |    |--- class1.h
        |    |--- class1.cpp
        |    |--- tst_class1.cpp
        |--- class2
        |     |--- class2.pro
        |     |--- class2.h
        |     |--- class2.cpp
        |     |--- tst_class2.cpp

SGaist · wrote on 5 Feb 2025, 19:34

It would rather be something like:

/FooApp
   |--- subdirs.pro
   |--- src
        |
        |--- app
        |    |--- app.pro
        |    |--- appname
        |        |--- appname.pro 
        |        |--- mainwindow.h 
        |        |--- mainwindow.cpp        
        |        |--- main.cpp
        |    |--- tests
        |        |--- tests.pro
        |            |--- tst_mainwindow
        |               |--- tst_mainwindow.pro
        |               |--- tst_mainwindow.cpp
        |--- lib
        |    |--- lib.pro
        |.   |--- mylib
        |.       |--- mylib.pro
        |        |--- class1.h
        |        |--- class1.cpp
        |        |--- class2.h
        |        |--- class2.cpp
        |    |--- tests
        |        |--- tests.pro
        |            |--- tst_class1
        |               |--- tst_class1.pro
        |               |--- tst_class1.cpp
        |            |--- tst_class2
        |               |--- tst_class2.pro
        |               |--- tst_class2.cpp

You can check the Qt sources structure to make yourself an idea.

Note that since it's a new project, you might want to move to cmake as qmake is deprecated.

ATE-ENGE · wrote on 5 Feb 2025, 20:03

Ok, I'll look to shift to cmake.
In terms of all those additional .pro files, How can I determine what should go in each?

SGaist · wrote on 5 Feb 2025, 20:05

The "folders" .pro files are subdirs projects while the leaf .pro files are either app, libs or tests projects.

ATE-ENGE · wrote on 6 Feb 2025, 18:04

Ok, with this structure I'm trying to build my tests/tst_class1/tst_class1.cpp However, I'm doing something wrong as my code is producing an unresolved external symbol error. I'm guessing I'm doing something wrong in the pro files.

lib.pro

TEMPLATE = subdirs

SUBDIRS += \
    mylib \
    tests

mylib.pro

QT += core gui sql network

CONFIG += c++17 cmdline testcase

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        class1.cpp \
        main.cpp

HEADERS += \
    class1.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

tests.pro

TEMPLATE = subdirs

SUBDIRS += \
    tst_class1

tst_class1.pro

QT += core gui sql network testlib

CONFIG += c++17 cmdline testcase

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    tst_class1.cpp \

INCLUDEPATH += ../../mylib/

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

Is there something I need to change?

SGaist · wrote on 6 Feb 2025, 19:45

You are not linking against the library you are testing.