tests: lib.ListUsers tests done

Even more coverage is on it's way. Have still to figure out in which
manner i'm going to test the things i want to.
It's actually not as easy as i expected...

private/test/test_ListUsers.py

@@ -0,0 +1,45 @@
+import unittest
+import test.testcfg as testcfg
+import sys
+import os
+from lib.ListUsers import ListUsers
+sys.path.append('..')
+
+f = open(os.devnull, 'w')
+sys.stdout = f
+
+
+class TestListUsers(unittest.TestCase):
+    def setUp(self) -> None:
+        try:
+            self.list = ListUsers(testcfg.test_db, unapproved=False, approved=False)
+        except IOError as fs_err:
+            self.fail(fs_err)
+
+    def test_output_as_list(self):
+        # count newlines in string, everything under 3 is wrong, and above 20 too.
+        out = self.list.output_as_list().splitlines()
+        self.assertGreater(len(out), testcfg.ListUsers_output_newlines,
+                           "Newlines in OUTPUT doesn't exceed minimum of at least "
+                           f"{testcfg.ListUsers_output_newlines} "
+                           "lines!")
+        print(out)
+
+    def test_pretty_print(self):
+        # wont going to compare the stdout sorry very much
+        return
+
+    def test_get_fetch(self):
+        fetch = self.list.get_fetch()
+        self.assertIsInstance(fetch, list)
+        self.assertGreater(len(fetch),
+                           testcfg.ListUsers_fetch_size_min, "fetch is NOT greater than"
+                                                             "the configured fetch minimum")
+        try:
+            print(fetch[0])
+        except (KeyError, IOError) as suddenly_not_there:
+            self.fail(f"Expected fetch to have at least one argument! {suddenly_not_there}")
+
+
+if __name__ == '__main__':
+    unittest.main()