diff --git a/test/hotp_generation_tests.erl b/test/hotp_generation_tests.erl
index eee96ba..4c659ea 100644
--- a/test/hotp_generation_tests.erl
+++ b/test/hotp_generation_tests.erl
@@ -3,50 +3,51 @@
 -include_lib("eunit/include/eunit.hrl").
 
 
-hotp_generation_from_secret_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun hotp_generation_from_secret/1}.
-
-
-hotp_generation_for_different_intervals_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun hotp_generation_for_different_intervals/1}.
-
-hotp_generation_with_padding_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun hotp_generation_with_padding/1}.
-
-hotp_generation_with_multiple_padding_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun hotp_generation_with_multiple_padding/1}.
+all_test_() ->
+    {foreach,
+     fun start/0,
+     fun stop/1,
+     [fun hotp_generation_from_secret/1,
+      fun hotp_generation_for_different_intervals/1,
+      fun hotp_generation_with_padding/1,
+      fun hotp_generation_with_multiple_padding/1,
+      fun hotp_generation_unsigned_interval/1]}.
 
 
 start() ->
-    ok.
+    #{secret1 => <<"MFRGGZDFMZTWQ2LK">>,
+      secret2 => <<"RWLMFU237M4RJIFA">>}.
 
 
 stop(_) ->
     ok.
 
 
-hotp_generation_from_secret(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+hotp_generation_from_secret(#{secret1 := Secret}) ->
     [?_assertEqual(pot:hotp(Secret, 1), <<"765705">>)].
 
 
-hotp_generation_for_different_intervals(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
-    [?_assertEqual(pot:hotp(Secret, 1), <<"765705">>),
+hotp_generation_for_different_intervals(#{secret1 := Secret}) ->
+    [?_assertEqual(pot:hotp(Secret, 0), <<"462371">>),
+     ?_assertEqual(pot:hotp(Secret, 1), <<"765705">>),
      ?_assertEqual(pot:hotp(Secret, 2), <<"816065">>)].
 
-hotp_generation_with_padding(_) ->
-   Secret = <<"MFRGGZDFMZTWQ2LK">>,
+
+hotp_generation_with_padding(#{secret1 := Secret}) ->
    [?_assertEqual(pot:hotp(Secret, 19), <<"088239">>)].
 
-hotp_generation_with_multiple_padding(_) ->
-   Secret = <<"RWLMFU237M4RJIFA">>,
+
+hotp_generation_with_multiple_padding(#{secret2 := Secret}) ->
    [?_assertEqual(pot:hotp(Secret, 48930987), <<"000371">>)].
+
+
+hotp_generation_unsigned_interval(#{secret1 := Secret}) ->
+    [{"negative intervals are equivalent to 64-bit unsigned representations (2^64 - 1)",
+      ?_assertEqual(pot:hotp(Secret,  18446744073709551615),
+                    pot:hotp(Secret, -1))},
+     {"negative intervals are equivalent to 64-bit unsigned representations (2^63 - 1)",
+      ?_assertEqual(pot:hotp(Secret,  9223372036854775808),
+                    pot:hotp(Secret, -9223372036854775808))},
+     {"large intervals are equivalent to 64-bit truncated representations (2^64 + 1)",
+      ?_assertEqual(pot:hotp(Secret, 18446744073709551617),
+                    pot:hotp(Secret, 1))}].
diff --git a/test/hotp_validity_tests.erl b/test/hotp_validity_tests.erl
index 7e694dd..bfdb561 100644
--- a/test/hotp_validity_tests.erl
+++ b/test/hotp_validity_tests.erl
@@ -11,6 +11,7 @@ checking_hotp_validity_without_range_test_() ->
      [fun checking_hotp_validity_without_range/1,
       fun checking_hotp_validity_max_default_range/1,
       fun checking_hotp_validity_past_max_default_range/1,
+      fun validatinging_invalid_token_hotp/1,
       fun validating_correct_hotp_after_exhaustion/1,
       fun validating_correct_totp_as_hotp/1,
       fun retrieving_proper_interval_from_validator/1,
@@ -40,6 +41,10 @@ checking_hotp_validity_past_max_default_range(Secret) ->
       ?_assertNot(pot:valid_hotp(pot:hotp(Secret, 1002), Secret))}].
 
 
+validatinging_invalid_token_hotp(Secret) ->
+     [?_assertNot(pot:valid_hotp(<<"abcdef">>, Secret))].
+
+
 validating_correct_hotp_after_exhaustion(Secret) ->
      [?_assertNot(pot:valid_hotp(pot:hotp(Secret, 123), Secret, [{last, 123}]))].
 
diff --git a/test/preliminary_check_tests.erl b/test/preliminary_check_tests.erl
index 26aecb6..962fcd1 100644
--- a/test/preliminary_check_tests.erl
+++ b/test/preliminary_check_tests.erl
@@ -3,16 +3,12 @@
 -include_lib("eunit/include/eunit.hrl").
 
 
-valid_token_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun valid_token/1}.
-
-
-variable_length_in_possible_token_test_() ->
-    {setup, fun start/0,
-            fun stop/1,
-            fun variable_length_in_possible_token/1}.
+all_test_() ->
+    {foreach,
+     fun start/0,
+     fun stop/1,
+     [fun valid_token/1,
+      fun variable_length_in_possible_token/1]}.
 
 
 start() ->
@@ -24,11 +20,11 @@ stop(_) ->
 
 
 valid_token(_) ->
-    [?_assertEqual(pot:valid_token(<<"123456">>), true),
-     ?_assertEqual(pot:valid_token(<<"abcdef">>), false),
-     ?_assertEqual(pot:valid_token(<<"12345678">>), false)].
+    [?_assert(pot:valid_token(<<"123456">>)),
+     ?_assertNot(pot:valid_token(<<"abcdef">>)),
+     ?_assertNot(pot:valid_token(<<"12345678">>))].
 
 
 variable_length_in_possible_token(_) ->
-    [?_assertEqual(pot:valid_token(<<"1234567">>), false),
-     ?_assertEqual(pot:valid_token(<<"1234567">>, [{token_length, 7}]), true)].
+    [?_assertNot(pot:valid_token(<<"1234567">>)),
+     ?_assert(pot:valid_token(<<"1234567">>, [{token_length, 7}]))].
diff --git a/test/totp_validity_tests.erl b/test/totp_validity_tests.erl
index 4b96089..b0a3d0d 100644
--- a/test/totp_validity_tests.erl
+++ b/test/totp_validity_tests.erl
@@ -9,36 +9,37 @@ totp_validity_test_() ->
      fun stop/1,
      [fun validating_totp_for_same_secret/1,
       fun validating_invalid_totp_for_same_secret/1,
+      fun validatinging_invalid_token_hotp/1,
       fun validating_correct_hotp_as_totp/1,
       fun validating_past_future_totp_too_small_window/1,
       fun validating_past_future_totp_with_window/1]}.
 
 
 start() ->
-    ok.
+    _Secret = <<"MFRGGZDFMZTWQ2LK">>.
 
 
 stop(_) ->
     ok.
 
 
-validating_totp_for_same_secret(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+validating_totp_for_same_secret(Secret) ->
     [?_assert(pot:valid_totp(pot:totp(Secret), Secret))].
 
 
-validating_invalid_totp_for_same_secret(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+validating_invalid_totp_for_same_secret(Secret) ->
     [?_assertNot(pot:valid_totp(<<"123456">>, Secret))].
 
 
-validating_correct_hotp_as_totp(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+validatinging_invalid_token_hotp(Secret) ->
+     [?_assertNot(pot:valid_totp(<<"abcdef">>, Secret))].
+
+
+validating_correct_hotp_as_totp(Secret) ->
     [?_assertNot(pot:valid_totp(pot:hotp(Secret, 1), Secret))].
 
 
-validating_past_future_totp_too_small_window(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+validating_past_future_totp_too_small_window(Secret) ->
     IntervalOpts = [{timestamp, os:timestamp()}],
     N = 5,
     [?_assertNot(pot:valid_totp(pot:totp(Secret, [{addwindow, AW} | IntervalOpts]),
@@ -47,8 +48,7 @@ validating_past_future_totp_too_small_window(_) ->
      || W <- lists:seq(0, N), AW <- lists:seq(-N, N), W < abs(AW)].
 
 
-validating_past_future_totp_with_window(_) ->
-    Secret = <<"MFRGGZDFMZTWQ2LK">>,
+validating_past_future_totp_with_window(Secret) ->
     IntervalOpts = [{timestamp, os:timestamp()}],
     N = 5,
     [?_assert(pot:valid_totp(pot:totp(Secret, [{addwindow, AW} | IntervalOpts]),