使用Qt进行单元测试：更改测试功能中使用的StandardPath

Question

I'm writing unit tests for a function in Qt.

My Code

I have a function that I want to test:

QSqlDatabase createDB() {
    QString database = "library";
    QString dbPath = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
    QDir appDataDir(dbPath);
    if (!appDataDir.exists()) {
        appDataDir.mkpath(dbPath);
    }
    dbPath += "/" + database + ".sqlite";
    QSqlDatabase db;
    db.setDatabaseName(dbPath);
    return db;
}

So in my test I have:

void DatabaseManagerTest::initTestCase()
{
    QStandardPaths::setTestModeEnabled(true);
}

void DatabaseManagerTest::testDb()
{
    QSqlDatabase m_db = createDb();
    QString database = "library";
    QString databasePath_exp = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation)
    + "/" + database + ".sqlite";

    QCOMPARE(m_db.databaseName(), databasePath_exp);
    qDebug() << m_db.databaseName();
}

QTEST_MAIN( DatabaseManagerTest )

The output of the test is

1: FAIL!  : DatabaseManagerTest::testDb() Compared values are not the same
1:    Actual   (m_db.databaseName()): "/home/olivier/.local/share/MyTest/library.sqlite"
1:    Expected (databasePath_exp)   : "/home/olivier/.qttest/share/MyTest/library.sqlite"

The Question

How can createDb() use the test StandardPaths of Qt and not the real ones?

Answer 1

A test should never use global variables, and "QStandardPaths::writableLocation" is a wrapper for a global variable. I don't think you can get out of this without injecting this dependency: you may:

• have "createDB()" to take the first part of path as a string parameter
• have "createDB()" to take a parameter of an abstract class 'pathLocator' with a virtual function 'getBasePath'. Production code will use a concrete child that returns "/home/olivier/.local/share/" while the test will use a mock child that returns "/home/olivier/.qttest/share/"