Qt: how to pass arguments to a Qt GUI test?

Qt: how to pass arguments to a Qt GUI test?
Basically, how to pass arguments to QTEST_MAIN as you could have done with regular main?

To run a test for testing a Qt GUI, one can do the following:

>> cat CMakeLists.txt 
cmake_minimum_required(VERSION 3.0)
project(foo)
enable_testing()
# Tell CMake to run moc when necessary:
set(CMAKE_AUTOMOC ON)
# As moc files are generated in the binary dir, tell CMake to always look for includes there:
set(CMAKE_INCLUDE_CURRENT_DIR ON)
find_package(Qt5Test REQUIRED)
add_executable(foo foo.cpp)
add_test(foo foo)
target_link_libraries(foo Qt5::Test)

>> cat foo.cpp 
#include <QTest>
class Foo : public QObject {
    Q_OBJECT
private slots:
    void t1() { QVERIFY(true); }
};
QTEST_MAIN(Foo)
#include "foo.moc"

>> mkdir build; cd build; cmake ..; make all test
[ 25%] Automatic MOC for target foo
[ 25%] Built target foo_autogen
[100%] Built target foo
Running tests...
Test project /tmp/test/build
    Start 1: foo
1/1 Test #1: foo ..............................   Passed    0.01 sec

100% tests passed, 0 tests failed out of 1

Total Test time (real) =   0.02 sec

Ok, so far, so good.

Now say I have to pass arguments to QTEST_MAIN in order to configure Foo and what's tested in t1: how to do this?

Basically, without Qt, one could have done:

set(TEST_MSG "hello" CACHE STRING "Message to print from Foo.")
add_test(NAME test COMMAND my_exe "${TEST_MSG}")

And then in the main of the test:

int main(int argc, char **argv) {
  std::string msg = argv[1];
  Foo f(msg);

Ideally, I'd like to run cmake like so cmake -D TEST_MSG=world .. and later on be able to retrieve the content of TEST_MSG (as a std::string) in Foo (to configure it): is it possible? If yes, how?

My understanding it that this reduces to "pass arguments to QTEST_MAIN": is this possible? And if yes, how to retrieve these arguments in the code (Foo)?

SOLUTION

Following @jdfa, this works:

>> git diff
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5c3c430..457ad7e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,5 +7,7 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 find_package(Qt5Test REQUIRED)
 add_executable(foo foo.cpp)
-add_test(foo foo)
 target_link_libraries(foo Qt5::Test)
+set(TEST_MSG "hello" CACHE STRING "Message to print from Foo.")
+add_test(NAME foo_tst COMMAND foo)
+set_property(TEST foo_tst PROPERTY ENVIRONMENT_MODIFICATION "TEST_MSG=set:${TEST_MSG}")
diff --git a/foo.cpp b/foo.cpp
index 844fca0..1d7e3da 100644
--- a/foo.cpp
+++ b/foo.cpp
@@ -1,8 +1,15 @@
 #include <QTest>
+#include <QtGlobal> // qgetenv
+#include <QString>
+#include <iostream> // cout
 class Foo : public QObject {
     Q_OBJECT
 private slots:
-    void t1() { QVERIFY(true); }
+    void t1() {
+      QString arg = qgetenv("TEST_MSG");
+      std::cout << "Foo arg: " << arg.toStdString() << std::endl;
+      QVERIFY(true);
+    }
 };
 QTEST_MAIN(Foo)
 #include "foo.moc"

There are few problems with your approach.

First of all, QTEST_MAIN creates tested object using default ctor. So even if you will create your own main function and will use QTEST_MAIN_IMPL instead of QTEST_MAIN - that will not help you to pass arguments to tested object.

Second issue is that QTest executable will interpret your additional arguments as test filter (QTest cli reference).

But there is another way to configure your test objects. You can use environment variables for that:

set(TEST_MSG "hello" CACHE STRING "Message to print from Foo.")
add_test(NAME test COMMAND my_exe "${TEST_MSG}")
set_property(TEST test  PROPERTY ENVIRONMENT_MODIFICATION "CUSTOM_ENV=set:${TEST_MSG}")

It will set CUSTOM_ENV variable with value ${TEST_MSG} for you test when it is started from ctest command. In tested object you can retrieve that value using qgetenv("CUSTOM_ENV"). So it will be possible to define default ctor and use it for any configuration.