[test_optimization] fix due to OMCPath usage

Author: syntron

tests/test_optimization.py

@@ -47,7 +47,9 @@ def test_optimization_example(tmp_path):
 
     r = mod.optimize()
     # it is necessary to specify resultfile, otherwise it wouldn't find it.
-    time, f, v = mod.getSolutions(["time", "f", "v"], resultfile=r["resultFile"])
+    resultfile_str = r["resultFile"]
+    resultfile_omcpath = mod._getconn.omcpath(resultfile_str)
+    time, f, v = mod.getSolutions(["time", "f", "v"], resultfile=resultfile_omcpath.as_posix())
     assert np.isclose(f[0], 10)
     assert np.isclose(f[-1], -10)