Add some testing of QTestEventLoop

Fairly minimal for now, just enough to verify a bug and serve as the
sign of success when it's fixed. Tests fail in ways they shouldn't,
for now; see expected_eventloop.* for details, notably "Earlier test
failed to clean up" messages.

Pick-to: 6.4 6.3
Task-number: QTBUG-104441
Change-Id: I59be4aa5f21fed23b19a0593a8c2f6c9956507df
Reviewed-by: Jason McDonald <macadder1@gmail.com>

2 files changed, 112 insertions, 0 deletions

diff --git a/tests/auto/testlib/selftests/eventloop/CMakeLists.txt b/tests/auto/testlib/selftests/eventloop/CMakeLists.txt
new file mode 100644
index 0000000000..f1fa9a788c
--- /dev/null
+++ b/tests/auto/testlib/selftests/eventloop/CMakeLists.txt
@@ -0,0 +1,16 @@
+#####################################################################
+## eventloop Binary:
+#####################################################################
+
+qt_internal_add_executable(eventloop
+    NO_INSTALL
+    OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+    SOURCES
+        tst_eventloop.cpp
+    PUBLIC_LIBRARIES
+        Qt::Test
+)
+
+## Scopes:
+#####################################################################
+qt_internal_apply_testlib_coverage_options(eventloop)
diff --git a/tests/auto/testlib/selftests/eventloop/tst_eventloop.cpp b/tests/auto/testlib/selftests/eventloop/tst_eventloop.cpp
new file mode 100644
index 0000000000..b5e8efce82
--- /dev/null
+++ b/tests/auto/testlib/selftests/eventloop/tst_eventloop.cpp
@@ -0,0 +1,96 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include <QTest>
+#include <QTestEventLoop>
+#include <QtCore/QTimer>
+
+// Tests for QTestEventLoop (and some QTRY_* details)
+class tst_EventLoop: public QObject
+{
+Q_OBJECT
+
+    bool m_inTestFunction = false;
+private slots:
+    void cleanup();
+    void fail();
+    void skip();
+    void pass();
+};
+
+class DeferredFlag
+{
+    bool m_flag;
+public:
+    explicit DeferredFlag(bool initial = false) : m_flag(initial)
+    {
+        if (!initial)
+            QTimer::singleShot(50, [this] { m_flag = true; });
+    }
+    explicit operator bool() const { return m_flag; }
+    bool operator!() const { return !m_flag; }
+    friend bool operator==(DeferredFlag a, DeferredFlag b) { return bool(a) == bool(b); }
+};
+
+char *toString(DeferredFlag val)
+{
+    return qstrdup(bool(val) ? "DeferredFlag(true)" : "DeferredFlag(false)");
+}
+
+void tst_EventLoop::cleanup()
+{
+    // QTBUG-104441: looping didn't happen in cleanup() if test failed or skipped.
+    {
+        DeferredFlag flag;
+        auto &loop = QTestEventLoop::instance();
+        loop.enterLoopMSecs(100);
+        QVERIFY2(loop.timeout(), "QTestEventLoop exited prematurely in cleanup()");
+        QVERIFY(flag);
+    }
+    {
+        DeferredFlag flag;
+        QTRY_VERIFY2(flag, "QTRY_* loop exited prematurely in cleanup()");
+    }
+
+    m_inTestFunction = false;
+}
+
+void tst_EventLoop::fail()
+{
+    QVERIFY2(!std::exchange(m_inTestFunction, true), "Earlier test failed to clean up");
+    QFAIL("Failing test should still clean up");
+}
+
+void tst_EventLoop::skip()
+{
+    QVERIFY2(!std::exchange(m_inTestFunction, true), "Earlier test failed to clean up");
+    QSKIP("Skipping test should still clean up");
+}
+
+void tst_EventLoop::pass()
+{
+    QVERIFY2(!std::exchange(m_inTestFunction, true), "Earlier test failed to clean up");
+    {
+        DeferredFlag flag;
+        auto &loop = QTestEventLoop::instance();
+        loop.enterLoopMSecs(100);
+        QVERIFY(loop.timeout());
+        QVERIFY(flag);
+    }
+    {
+        DeferredFlag flag;
+        QTRY_VERIFY(flag);
+    }
+    DeferredFlag flag;
+    QTestEventLoop loop(this);
+    QVERIFY(!flag);
+    loop.enterLoopMSecs(1);
+    QVERIFY(loop.timeout());
+    QVERIFY(!flag);
+    loop.enterLoopMSecs(100);
+    QVERIFY(loop.timeout());
+    QVERIFY(flag);
+}
+
+QTEST_MAIN(tst_EventLoop)
+#include "tst_eventloop.moc"