Fixed non-regression tests.

In some cases (as observed for macOS), numerical artefacts could produce a very low value when 0.0 was expected.

tests/integration_tests/oad_process/test_oad_process.py

@@ -204,13 +204,11 @@ def run_non_regression_test(
     pd.set_option("display.max_colwidth", 120)
     print(df.sort_values(by=["abs_rel_delta"]))
 
+    assert_allclose(df.value, df.ref_value, rtol=global_tolerance, atol=1.0e-9)
     if vars_to_check is not None:
         for name in vars_to_check:
-            assert_allclose(df.ref_value, df.value, rtol=global_tolerance)
             row = df.loc[df.name == name]
-            assert_allclose(row.ref_value, row.value, rtol=specific_tolerance)
-    else:
-        assert np.all(df.abs_rel_delta < specific_tolerance)
+            assert_allclose(row.value, row.ref_value, rtol=specific_tolerance, atol=1.0e-9)
 
 
 def test_api_eval_breguet(cleanup):