Add more optimization tests (#171)

* Integrated single_test_optimization into pytest to run a basic optimization test with tolerance set to 1e-6, ensuring quick detection of deviations.
* Added a long-run test (400 generations, like single_test_optimization), which can be triggered using --full-run in pytest.
* Mocked PDF creation in optimization tests and added a new PDF generation test with image comparison validation.

Note: Current tolerance is set to 1e-6; feedback on whether this tolerance is tight enough is welcome.

---------

Co-authored-by: Normann <github@koldrack.com>
Co-authored-by: Michael Osthege <michael.osthege@outlook.com>

tests/conftest.py

@@ -6,6 +6,17 @@ import pytest
 from xprocess import ProcessStarter
 
 
+def pytest_addoption(parser):
+    parser.addoption(
+        "--full-run", action="store_true", default=False, help="Run with all optimization tests."
+    )
+
+
+@pytest.fixture
+def is_full_run(request):
+    yield bool(request.config.getoption("--full-run"))
+
+
 @pytest.fixture
 def server(xprocess):
     class Starter(ProcessStarter):