Fix: Add algorithm name validation in OsipiBase.osipi_initiate_algorithm()

src/wrappers/OsipiBase.py

@@ -145,19 +145,60 @@ def osipi_initiate_algorithm(self, algorithm, **kwargs):
 
         Args:
             algorithm (string): The name of the algorithm, should be the same as the file in the src/standardized folder without the .py extension.
+
+        Raises:
+            ValueError: If the algorithm name does not correspond to any .py file
+                        in ``src/standardized/``.
         """
 
         # Import the algorithm
         root_path = pathlib.Path(__file__).resolve().parents[2]
         if str(root_path) not in sys.path:
-            print("Root folder not in PYTHONPATH")
-            return False
-
+            raise RuntimeError(
+                "Root folder not found in PYTHONPATH. "
+                "Please ensure the project root is in sys.path."
+            )
+
+        # ------------------------------------------------------------------
+        # Validate algorithm name against available modules in src/standardized/
+        # ------------------------------------------------------------------
+        standardized_dir = root_path / "src" / "standardized"
+        available_algorithms = sorted(
+            p.stem
+            for p in standardized_dir.glob("*.py")
+            if p.stem != "__init__"
+        )
+
+        if algorithm not in available_algorithms:
+            raise ValueError(
+                f"Algorithm '{algorithm}' not found. "
+                f"Available algorithms are:\n  "
+                + "\n  ".join(available_algorithms)
+            )
+
         import_base_path = "src.standardized"
         import_path = import_base_path + "." + algorithm
-        #Algorithm = getattr(importlib.import_module(import_path), algorithm)
+
+        # Secondary safety net: catch import / attribute errors that could
+        # occur if the file exists but is broken or missing the class.
+        try:
+            module = importlib.import_module(import_path)
+        except ImportError as exc:
+            raise ImportError(
+                f"Failed to import module for algorithm '{algorithm}': {exc}"
+            ) from exc
+
+        try:
+            algorithm_class = getattr(module, algorithm)
+        except AttributeError as exc:
+            raise AttributeError(
+                f"Module '{import_path}' was imported but does not contain "
+                f"a class named '{algorithm}'. "
+                f"Available names: {[n for n in dir(module) if not n.startswith('_')]}"
+            ) from exc
+
         # Change the class from OsipiBase to the specified algorithm
-        self.__class__ = getattr(importlib.import_module(import_path), algorithm)
+        self.__class__ = algorithm_class
         self.__init__(**kwargs)
 
     def initialize(**kwargs):

tests/IVIMmodels/unit_tests/test_ivim_fit.py

@@ -300,3 +300,28 @@ def to_list_if_needed(value):
     if errors:
         all_errors = "\n".join(errors)
         raise AssertionError(f"Some tests failed:\n{all_errors}")
+
+
+def test_invalid_algorithm_name():
+    """Regression test for bug_7: invalid algorithm names must raise a clear
+    ValueError instead of a confusing ModuleNotFoundError / AttributeError.
+    """
+    # A clearly wrong name should raise ValueError
+    with pytest.raises(ValueError, match="not found"):
+        OsipiBase(algorithm="IAR_LU_biepx")  # typo: 'biepx' instead of 'biexp'
+
+    # The error message should list at least one known valid algorithm
+    try:
+        OsipiBase(algorithm="totally_fake_algorithm")
+    except ValueError as exc:
+        error_msg = str(exc)
+        assert "Available algorithms are:" in error_msg
+        # Check a few known algorithms appear in the suggestion list
+        assert "IAR_LU_biexp" in error_msg
+        assert "PV_MUMC_biexp" in error_msg
+    else:
+        pytest.fail("ValueError was not raised for a completely invalid algorithm name")
+
+    # A valid algorithm should still work without errors
+    fit = OsipiBase(algorithm="IAR_LU_biexp")
+    assert fit is not None