diff --git a/ex4.py b/ex4.py
new file mode 100644
index 0000000..d04bf79
--- /dev/null
+++ b/ex4.py
@@ -0,0 +1,15 @@
+import numpy as np
+
+
+def ex4(image_array: np.array, offset: (int, int), spacing: (int, int)):
+    mask = np.zeros(shape=image_array.shape, dtype=image_array.dtype)
+    test = list(range(offset[0], mask.shape[1] - 1, spacing[0]))
+    print(test)
+    pass
+
+
+if __name__ == '__main__':
+    ex4(np.array([[(0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0)],
+                  [(0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0)],
+                  [(0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0)]
+                  ]), offset=(1, 1), spacing=(2, 2))
diff --git a/ex4_unittest.py b/ex4_unittest.py
new file mode 100644
index 0000000..ec1215e
--- /dev/null
+++ b/ex4_unittest.py
@@ -0,0 +1,143 @@
+"""
+Author -- Michael Widrich
+Contact -- widrich@ml.jku.at
+Date -- 01.10.2019
+
+###############################################################################
+
+The following copyright statement applies to all code within this file.
+
+Copyright statement:
+This  material,  no  matter  whether  in  printed  or  electronic  form,
+may  be  used  for personal  and non-commercial educational use only.
+Any reproduction of this manuscript, no matter whether as a whole or in parts,
+no matter whether in printed or in electronic form, requires explicit prior
+acceptance of the authors.
+
+###############################################################################
+
+"""
+
+import os
+import sys
+import traceback
+
+import dill as pkl
+import numpy as np
+
+
+def print_outs(outs, line_token="-"):
+    print(line_token * 40)
+    print(outs, end="" if isinstance(outs, str) and outs.endswith("\n") else "\n")
+    print(line_token * 40)
+
+
+ex_file = 'ex4.py'
+full_points = 20
+points = full_points
+python = sys.executable
+
+with open(os.path.join("unittest", "unittest_inputs_outputs.pkl"), "rb") as ufh:
+    all_inputs_outputs = pkl.load(ufh)
+    all_inputs = all_inputs_outputs['inputs']
+    all_outputs = all_inputs_outputs['outputs']
+
+feedback = ''
+
+for test_i, (inputs, outputs) in enumerate(zip(all_inputs, all_outputs)):
+    
+    comment = ''
+    fcall = ''
+    with open(os.devnull, 'w') as null:
+        # sys.stdout = null
+        try:
+            from ex4 import ex4
+            proper_import = True
+        except Exception:
+            outs = ''
+            errs = traceback.format_exc()
+            points -= full_points / len(all_inputs_outputs)
+            proper_import = False
+        finally:
+            sys.stdout.flush()
+            sys.stdout = sys.__stdout__
+    
+    if proper_import:
+        with open(os.devnull, 'w') as null:
+            # sys.stdout = null
+            try:
+                errs = ''
+                fcall = f"ex4(image_array={inputs[0]}, offset={inputs[1]}, spacing={inputs[2]}))"
+                returns = ex4(image_array=inputs[0], offset=inputs[1],
+                              spacing=inputs[2])
+
+                # Check if returns and outputs are of same type
+                if type(returns) != type(outputs):
+                    comment = f"Output should be: {type(outputs).__name__} ('{outputs}'). \n" \
+                              f"          but is: {returns}"
+                    points -= full_points / len(all_inputs)
+                else:
+                    # Check input_array output
+                    if (len(returns) != 3
+                            or not isinstance(returns[0], np.ndarray)
+                            or returns[0].dtype != outputs[0].dtype
+                            or returns[0].shape != outputs[0].shape
+                            or np.any(returns[0] != outputs[0])):
+                        points -= (full_points / len(all_inputs)) / 3
+                        comment = f"Incorrect 'input_array'. Output should be: " \
+                                f"{outputs} \n" \
+                                f"but is {returns}"
+                    
+                    # Check known_array output
+                    if (len(returns) != 3
+                            or not isinstance(returns[1], np.ndarray)
+                            or returns[1].dtype != outputs[1].dtype
+                            or returns[1].shape != outputs[1].shape
+                            or np.any(returns[1] != outputs[1])):
+                        points -= (full_points / len(all_inputs)) / 3
+                        comment = f"Incorrect 'known_array'. Output should be: " \
+                                f"{outputs} \n" \
+                                f"but is {returns}"
+                    
+                    # Check target_array output
+                    if (len(returns) != 3
+                            or not isinstance(returns[2], np.ndarray)
+                            or returns[2].dtype != outputs[2].dtype
+                            or returns[2].shape != outputs[2].shape
+                            or np.any(returns[2] != outputs[2])):
+                        points -= (full_points / len(all_inputs)) / 3
+                        comment = f"Incorrect 'target_array'. Output should be: " \
+                                f"{outputs} \n" \
+                                f"but is {returns}"
+            
+            except Exception as e:
+                outs = ''
+                if not type(e) == type(outputs):
+                    comment = f"Output should be: {type(outputs).__name__} ('{outputs}'). \n" \
+                              f"          but is:\n{traceback.format_exc()}"
+                    points -= full_points / len(all_inputs)
+            finally:
+                sys.stdout.flush()
+                sys.stdout = sys.__stdout__
+    
+    print()
+    print_outs(f"Test {test_i}", line_token="#")
+    print("Function call:")
+    print_outs(fcall)
+
+    if errs:
+        print(f"Some unexpected errors occurred:")
+        print_outs(errs)
+    else:
+        print("Notes:")
+        print_outs("No issues found" if comment == "" else comment)
+
+    # due to floating point calculations it could happen that we get -0 here
+    if points < 0:
+        assert abs(points) < 1e-7, f"points were {points} < 0: error when subtracting points?"
+        points = 0
+    print(f"Current points: {points:.2f}")
+
+print(f"\nEstimated points upon submission: {points:.2f} (out of {full_points:.2f})")
+print(f"This is only an estimate, see 'Instructions for submitting homework' in Moodle "
+      f"for common mistakes that can still lead to 0 points.")