Fix #28: Make test more robust (#35)

Modify the `test` function to validate the test table and confirm: 
 - the test table is a list or tuple
 - each test case from the test table is list or tuple
 - the first element of each case is a string
 - each test case has the correct number of args

src/algoesup/test.py

@@ -8,20 +8,43 @@ def test(function: Callable, test_table: list) -> None:
 
     Args:
         function (Callable): The function to be tested.
-        test_table (list): The list of tests. Each element of test_table is a list or 
+        test_table (list): The list of tests. Each element of test_table is a list or
             tuple with: a string (the test case name); one or more values (the inputs to the function);
             the expected output value.
     """
-    print(f"Testing {function.__name__}...")
-    passed = failed = 0
-    for test_case in test_table:
-        name = test_case[0]
-        inputs = test_case[1:-1]
-        expected = test_case[-1]
-        actual = function(*inputs)
-        if actual != expected:
-            print(name, "FAILED:", actual, "instead of", expected)
-            failed += 1
-        else:
-            passed += 1
-    print("Tests finished:", passed, "passed,", failed, "failed.")
+    not_tested = f"The test table is invalid, {function.__name__} has NOT been tested."
+    if not isinstance(test_table, (list, tuple)):
+        print(f"Error: The test table must be a list or tuple.\n{not_tested}")
+        return
+    # The number of arguments function expects.
+    expects = function.__code__.co_argcount
+    invalid = []
+    for num, test_case in enumerate(test_table, start=1):
+        if not isinstance(test_case, (list, tuple)):
+            invalid.append(f"test case {num} must be a list or tuple.")
+        elif not isinstance(test_case[0], str):
+            invalid.append(f"test case {num} must have string as first element.")
+        elif len(test_case[1:-1]) != expects:
+            num_args = len(test_case[1:-1])
+            invalid.append(
+                f'test case "{test_case[0]}" has {num_args} input(s) instead of {expects}'
+            )
+    if invalid:
+        for msg in invalid:
+            print(f"Error: {msg}")
+        print(not_tested)
+        return
+    else:
+        print(f"Testing {function.__name__}...")
+        passed = failed = 0
+        for test_case in test_table:
+            name = test_case[0]
+            inputs = test_case[1:-1]
+            expected = test_case[-1]
+            actual = function(*inputs)
+            if actual != expected:
+                print(name, "FAILED:", actual, "instead of", expected)
+                failed += 1
+            else:
+                passed += 1
+        print("Tests finished:", passed, "passed,", failed, "failed.")