Method buffer_fromFile_nonexistent

tests/test_provider.cpp:240–244

    // ---------------------------------------------------------------

    void buffer_fromFile_nonexistent() {
        auto p = BufferProvider::fromFile("/tmp/__rcx_test_nonexistent_file__");
        QVERIFY(!p.isValid());
        QCOMPARE(p.size(), 0);
    }

    void buffer_fromFile_valid() {
        // Write a temp file, read it back