diff --git a/substrate/frame/elections-phragmen/src/lib.rs b/substrate/frame/elections-phragmen/src/lib.rs
index 036a5f492c..f0d08f6164 100644
--- a/substrate/frame/elections-phragmen/src/lib.rs
+++ b/substrate/frame/elections-phragmen/src/lib.rs
@@ -1083,7 +1083,7 @@ mod tests {
 			self.genesis_members = members;
 			self
 		}
-		pub fn build(self) -> sp_io::TestExternalities {
+		pub fn build_and_execute(self, test: impl FnOnce() -> ()) {
 			VOTING_BOND.with(|v| *v.borrow_mut() = self.voter_bond);
 			TERM_DURATION.with(|v| *v.borrow_mut() = self.term_duration);
 			DESIRED_RUNNERS_UP.with(|v| *v.borrow_mut() = self.desired_runners_up);
@@ -1103,8 +1103,9 @@ mod tests {
 					members: self.genesis_members
 				}),
 			}.build_storage().unwrap().into();
-			ext.execute_with(|| System::set_block_number(1));
-			ext
+			ext.execute_with(pre_conditions);
+			ext.execute_with(test);
+			ext.execute_with(post_conditions)
 		}
 	}
 
@@ -1122,9 +1123,55 @@ mod tests {
 		lock.amount
 	}
 
+	fn intersects<T: PartialEq>(a: &[T], b: &[T]) -> bool {
+		a.iter().any(|e| b.contains(e))
+	}
+
+	fn ensure_members_sorted() {
+		let mut members = Elections::members().clone();
+		members.sort();
+		assert_eq!(Elections::members(), members);
+	}
+
+	fn ensure_candidates_sorted() {
+		let mut candidates = Elections::candidates().clone();
+		candidates.sort();
+		assert_eq!(Elections::candidates(), candidates);
+	}
+
+	fn ensure_members_has_approval_stake() {
+		// we filter members that have no approval state. This means that even we have more seats
+		// than candidates, we will never ever chose a member with no votes.
+		assert!(
+			Elections::members().iter().chain(
+				Elections::runners_up().iter()
+			).all(|(_, s)| *s != Zero::zero())
+		);
+	}
+
+	fn ensure_member_candidates_runners_up_disjoint() {
+		// members, candidates and runners-up must always be disjoint sets.
+		assert!(!intersects(&Elections::members_ids(), &Elections::candidates()));
+		assert!(!intersects(&Elections::members_ids(), &Elections::runners_up_ids()));
+		assert!(!intersects(&Elections::candidates(), &Elections::runners_up_ids()));
+	}
+
+	fn pre_conditions() {
+		System::set_block_number(1);
+		ensure_members_sorted();
+		ensure_candidates_sorted();
+	}
+
+	fn post_conditions() {
+		ensure_members_sorted();
+		ensure_candidates_sorted();
+		ensure_member_candidates_runners_up_disjoint();
+		ensure_members_has_approval_stake();
+	}
+
 	#[test]
 	fn params_should_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::desired_members(), 2);
 			assert_eq!(Elections::term_duration(), 5);
 			assert_eq!(Elections::election_rounds(), 0);
@@ -1143,7 +1190,7 @@ mod tests {
 
 	#[test]
 	fn genesis_members_should_work() {
-		ExtBuilder::default().genesis_members(vec![(1, 10), (2, 20)]).build().execute_with(|| {
+		ExtBuilder::default().genesis_members(vec![(1, 10), (2, 20)]).build_and_execute(|| {
 			System::set_block_number(1);
 			assert_eq!(Elections::members(), vec![(1, 10), (2, 20)]);
 
@@ -1160,7 +1207,7 @@ mod tests {
 
 	#[test]
 	fn genesis_members_unsorted_should_work() {
-		ExtBuilder::default().genesis_members(vec![(2, 20), (1, 10)]).build().execute_with(|| {
+		ExtBuilder::default().genesis_members(vec![(2, 20), (1, 10)]).build_and_execute(|| {
 			System::set_block_number(1);
 			assert_eq!(Elections::members(), vec![(1, 10), (2, 20)]);
 
@@ -1179,28 +1226,27 @@ mod tests {
 	#[should_panic = "Genesis member does not have enough stake"]
 	fn genesis_members_cannot_over_stake_0() {
 		// 10 cannot lock 20 as their stake and extra genesis will panic.
-		ExtBuilder::default().genesis_members(vec![(1, 20), (2, 20)]).build();
+		ExtBuilder::default().genesis_members(vec![(1, 20), (2, 20)]).build_and_execute(|| {});
 	}
 
 	#[test]
 	#[should_panic]
 	fn genesis_members_cannot_over_stake_1() {
 		// 10 cannot reserve 20 as voting bond and extra genesis will panic.
-		ExtBuilder::default().voter_bond(20).genesis_members(vec![(1, 10), (2, 20)]).build();
+		ExtBuilder::default().voter_bond(20).genesis_members(vec![(1, 10), (2, 20)]).build_and_execute(|| {});
 	}
 
 	#[test]
 	#[should_panic = "Duplicate member in elections phragmen genesis: 2"]
 	fn genesis_members_cannot_be_duplicate() {
-		ExtBuilder::default().genesis_members(vec![(1, 10), (2, 10), (2, 10)]).build();
+		ExtBuilder::default().genesis_members(vec![(1, 10), (2, 10), (2, 10)]).build_and_execute(|| {});
 	}
 
 	#[test]
 	fn term_duration_zero_is_passive() {
 		ExtBuilder::default()
 			.term_duration(0)
-			.build()
-			.execute_with(||
+			.build_and_execute(||
 		{
 			assert_eq!(Elections::term_duration(), 0);
 			assert_eq!(Elections::desired_members(), 2);
@@ -1221,7 +1267,7 @@ mod tests {
 
 	#[test]
 	fn simple_candidate_submission_should_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert!(Elections::is_candidate(&1).is_err());
 			assert!(Elections::is_candidate(&2).is_err());
@@ -1248,7 +1294,7 @@ mod tests {
 
 	#[test]
 	fn simple_candidate_submission_with_no_votes_should_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 
 			assert_ok!(Elections::submit_candidacy(Origin::signed(1)));
@@ -1275,7 +1321,7 @@ mod tests {
 
 	#[test]
 	fn dupe_candidate_submission_should_not_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert_ok!(Elections::submit_candidacy(Origin::signed(1)));
 			assert_eq!(Elections::candidates(), vec![1]);
@@ -1289,7 +1335,7 @@ mod tests {
 	#[test]
 	fn member_candidacy_submission_should_not_work() {
 		// critically important to make sure that outgoing candidates and losers are not mixed up.
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::vote(Origin::signed(2), vec![5], 20));
 
@@ -1309,7 +1355,7 @@ mod tests {
 
 	#[test]
 	fn runner_candidate_submission_should_not_work() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1332,7 +1378,7 @@ mod tests {
 
 	#[test]
 	fn poor_candidate_submission_should_not_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert_noop!(
 				Elections::submit_candidacy(Origin::signed(7)),
@@ -1343,7 +1389,7 @@ mod tests {
 
 	#[test]
 	fn simple_voting_should_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert_eq!(balances(&2), (20, 0));
 
@@ -1357,7 +1403,7 @@ mod tests {
 
 	#[test]
 	fn can_vote_with_custom_stake() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(Elections::candidates(), Vec::<u64>::new());
 			assert_eq!(balances(&2), (20, 0));
 
@@ -1371,7 +1417,7 @@ mod tests {
 
 	#[test]
 	fn can_update_votes_and_stake() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(balances(&2), (20, 0));
 
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
@@ -1392,7 +1438,7 @@ mod tests {
 
 	#[test]
 	fn cannot_vote_for_no_candidate() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_noop!(
 				Elections::vote(Origin::signed(2), vec![], 20),
 				Error::<Test>::UnableToVote,
@@ -1402,7 +1448,7 @@ mod tests {
 
 	#[test]
 	fn can_vote_for_old_members_even_when_no_new_candidates() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1420,7 +1466,7 @@ mod tests {
 
 	#[test]
 	fn prime_works() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
@@ -1444,7 +1490,7 @@ mod tests {
 
 	#[test]
 	fn prime_votes_for_exiting_members_are_removed() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
@@ -1469,7 +1515,7 @@ mod tests {
 
 	#[test]
 	fn cannot_vote_for_more_than_candidates() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1482,7 +1528,7 @@ mod tests {
 
 	#[test]
 	fn cannot_vote_for_less_than_ed() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1495,7 +1541,7 @@ mod tests {
 
 	#[test]
 	fn can_vote_for_more_than_total_balance_but_moot() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1508,7 +1554,7 @@ mod tests {
 
 	#[test]
 	fn remove_voter_should_work() {
-		ExtBuilder::default().voter_bond(8).build().execute_with(|| {
+		ExtBuilder::default().voter_bond(8).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 
 			assert_ok!(Elections::vote(Origin::signed(2), vec![5], 20));
@@ -1533,14 +1579,14 @@ mod tests {
 
 	#[test]
 	fn non_voter_remove_should_not_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_noop!(Elections::remove_voter(Origin::signed(3)), Error::<Test>::MustBeVoter);
 		});
 	}
 
 	#[test]
 	fn dupe_remove_should_fail() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::vote(Origin::signed(2), vec![5], 20));
 
@@ -1553,7 +1599,7 @@ mod tests {
 
 	#[test]
 	fn removed_voter_should_not_be_counted() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1573,7 +1619,7 @@ mod tests {
 
 	#[test]
 	fn reporter_must_be_voter() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_noop!(
 				Elections::report_defunct_voter(Origin::signed(1), 2),
 				Error::<Test>::MustBeVoter,
@@ -1583,7 +1629,7 @@ mod tests {
 
 	#[test]
 	fn can_detect_defunct_voter() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(6)));
@@ -1622,7 +1668,7 @@ mod tests {
 
 	#[test]
 	fn report_voter_should_work_and_earn_reward() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1653,7 +1699,7 @@ mod tests {
 
 	#[test]
 	fn report_voter_should_slash_when_bad_report() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1682,7 +1728,7 @@ mod tests {
 
 	#[test]
 	fn simple_voting_rounds_should_work() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1717,7 +1763,7 @@ mod tests {
 
 	#[test]
 	fn defunct_voter_will_be_counted() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 
 			// This guy's vote is pointless for this round.
@@ -1745,7 +1791,7 @@ mod tests {
 
 	#[test]
 	fn only_desired_seats_are_chosen() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1766,7 +1812,7 @@ mod tests {
 
 	#[test]
 	fn phragmen_should_not_self_vote() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1781,7 +1827,7 @@ mod tests {
 
 	#[test]
 	fn runners_up_should_be_kept() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1808,7 +1854,7 @@ mod tests {
 
 	#[test]
 	fn runners_up_should_be_next_candidates() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1835,7 +1881,7 @@ mod tests {
 
 	#[test]
 	fn runners_up_lose_bond_once_outgoing() {
-		ExtBuilder::default().desired_runners_up(1).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(1).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(2)));
@@ -1863,7 +1909,7 @@ mod tests {
 
 	#[test]
 	fn members_lose_bond_once_outgoing() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_eq!(balances(&5), (50, 0));
 
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
@@ -1889,7 +1935,7 @@ mod tests {
 
 	#[test]
 	fn losers_will_lose_the_bond() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
 
@@ -1912,7 +1958,7 @@ mod tests {
 
 	#[test]
 	fn current_members_are_always_next_candidate() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -1948,7 +1994,7 @@ mod tests {
 	fn election_state_is_uninterrupted() {
 		// what I mean by uninterrupted:
 		// given no input or stimulants the same members are re-elected.
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -1981,7 +2027,7 @@ mod tests {
 
 	#[test]
 	fn remove_members_triggers_election() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -2007,7 +2053,7 @@ mod tests {
 
 	#[test]
 	fn seats_should_be_released_when_no_vote() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -2041,7 +2087,7 @@ mod tests {
 
 	#[test]
 	fn incoming_outgoing_are_reported() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 
@@ -2088,7 +2134,7 @@ mod tests {
 
 	#[test]
 	fn invalid_votes_are_moot() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
 
@@ -2106,7 +2152,7 @@ mod tests {
 
 	#[test]
 	fn members_are_sorted_based_on_id_runners_on_merit() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -2128,7 +2174,7 @@ mod tests {
 
 	#[test]
 	fn candidates_are_sorted() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
 
@@ -2144,7 +2190,7 @@ mod tests {
 
 	#[test]
 	fn runner_up_replacement_maintains_members_order() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(2)));
@@ -2164,7 +2210,7 @@ mod tests {
 
 	#[test]
 	fn runner_up_replacement_works_when_out_of_order() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -2185,7 +2231,7 @@ mod tests {
 
 	#[test]
 	fn can_renounce_candidacy_member_with_runners_bond_is_refunded() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -2212,7 +2258,7 @@ mod tests {
 
 	#[test]
 	fn can_renounce_candidacy_member_without_runners_bond_is_refunded() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 
@@ -2244,7 +2290,7 @@ mod tests {
 
 	#[test]
 	fn can_renounce_candidacy_runner() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(4)));
 			assert_ok!(Elections::submit_candidacy(Origin::signed(3)));
@@ -2271,7 +2317,7 @@ mod tests {
 
 	#[test]
 	fn can_renounce_candidacy_candidate() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_ok!(Elections::submit_candidacy(Origin::signed(5)));
 			assert_eq!(balances(&5), (47, 3));
 			assert_eq!(Elections::candidates(), vec![5]);
@@ -2284,7 +2330,7 @@ mod tests {
 
 	#[test]
 	fn wrong_renounce_candidacy_should_fail() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			assert_noop!(
 				Elections::renounce_candidacy(Origin::signed(5)),
 				Error::<Test>::InvalidOrigin,
@@ -2294,7 +2340,7 @@ mod tests {
 
 	#[test]
 	fn behavior_with_dupe_candidate() {
-		ExtBuilder::default().desired_runners_up(2).build().execute_with(|| {
+		ExtBuilder::default().desired_runners_up(2).build_and_execute(|| {
 			<Candidates<Test>>::put(vec![1, 1, 2, 3, 4]);
 
 			assert_ok!(Elections::vote(Origin::signed(5), vec![1], 50));
diff --git a/substrate/frame/staking/src/lib.rs b/substrate/frame/staking/src/lib.rs
index da860bd63e..bc2721bc9f 100644
--- a/substrate/frame/staking/src/lib.rs
+++ b/substrate/frame/staking/src/lib.rs
@@ -1184,7 +1184,6 @@ decl_module! {
 							} else {
 								log!(warn, "💸 Failed to create snapshot at {:?}.", now);
 							}
-
 						}
 					}
 				} else {
diff --git a/substrate/frame/staking/src/mock.rs b/substrate/frame/staking/src/mock.rs
index 6332486b65..8e2b583c5e 100644
--- a/substrate/frame/staking/src/mock.rs
+++ b/substrate/frame/staking/src/mock.rs
@@ -42,25 +42,25 @@ const INIT_TIMESTAMP: u64 = 30_000;
 pub(crate) type AccountId = u64;
 pub(crate) type AccountIndex = u64;
 pub(crate) type BlockNumber = u64;
-pub(crate) type Balance = u64;
+pub(crate) type Balance = u128;
 
 /// Simple structure that exposes how u64 currency can be represented as... u64.
 pub struct CurrencyToVoteHandler;
-impl Convert<u64, u64> for CurrencyToVoteHandler {
-	fn convert(x: u64) -> u64 {
-		x
+impl Convert<Balance, u64> for CurrencyToVoteHandler {
+	fn convert(x: Balance) -> u64 {
+		x.saturated_into()
 	}
 }
-impl Convert<u128, u64> for CurrencyToVoteHandler {
-	fn convert(x: u128) -> u64 {
-		x.saturated_into()
+impl Convert<u128, Balance> for CurrencyToVoteHandler {
+	fn convert(x: u128) -> Balance {
+		x
 	}
 }
 
 thread_local! {
 	static SESSION: RefCell<(Vec<AccountId>, HashSet<AccountId>)> = RefCell::new(Default::default());
 	static SESSION_PER_ERA: RefCell<SessionIndex> = RefCell::new(3);
-	static EXISTENTIAL_DEPOSIT: RefCell<u64> = RefCell::new(0);
+	static EXISTENTIAL_DEPOSIT: RefCell<Balance> = RefCell::new(0);
 	static SLASH_DEFER_DURATION: RefCell<EraIndex> = RefCell::new(0);
 	static ELECTION_LOOKAHEAD: RefCell<BlockNumber> = RefCell::new(0);
 	static PERIOD: RefCell<BlockNumber> = RefCell::new(1);
@@ -104,8 +104,8 @@ pub fn is_disabled(controller: AccountId) -> bool {
 }
 
 pub struct ExistentialDeposit;
-impl Get<u64> for ExistentialDeposit {
-	fn get() -> u64 {
+impl Get<Balance> for ExistentialDeposit {
+	fn get() -> Balance {
 		EXISTENTIAL_DEPOSIT.with(|v| *v.borrow())
 	}
 }
@@ -172,8 +172,8 @@ impl_outer_event! {
 
 /// Author of block is always 11
 pub struct Author11;
-impl FindAuthor<u64> for Author11 {
-	fn find_author<'a, I>(_digests: I) -> Option<u64>
+impl FindAuthor<AccountId> for Author11 {
+	fn find_author<'a, I>(_digests: I) -> Option<AccountId>
 		where I: 'a + IntoIterator<Item = (frame_support::ConsensusEngineId, &'a [u8])>,
 	{
 		Some(11)
@@ -207,7 +207,7 @@ impl frame_system::Trait for Test {
 	type MaximumBlockLength = MaximumBlockLength;
 	type Version = ();
 	type ModuleToIndex = ();
-	type AccountData = pallet_balances::AccountData<u64>;
+	type AccountData = pallet_balances::AccountData<Balance>;
 	type OnNewAccount = ();
 	type OnKilledAccount = ();
 }
@@ -337,7 +337,7 @@ impl Default for ExtBuilder {
 }
 
 impl ExtBuilder {
-	pub fn existential_deposit(mut self, existential_deposit: u64) -> Self {
+	pub fn existential_deposit(mut self, existential_deposit: Balance) -> Self {
 		self.existential_deposit = existential_deposit;
 		self
 	}
@@ -369,7 +369,7 @@ impl ExtBuilder {
 		self.num_validators = Some(num_validators);
 		self
 	}
-	pub fn invulnerables(mut self, invulnerables: Vec<u64>) -> Self {
+	pub fn invulnerables(mut self, invulnerables: Vec<AccountId>) -> Self {
 		self.invulnerables = invulnerables;
 		self
 	}
@@ -415,7 +415,7 @@ impl ExtBuilder {
 
 		let num_validators = self.num_validators.unwrap_or(self.validator_count);
 		let validators = (0..num_validators)
-			.map(|x| ((x + 1) * 10 + 1) as u64)
+			.map(|x| ((x + 1) * 10 + 1) as AccountId)
 			.collect::<Vec<_>>();
 
 		let _ = pallet_balances::GenesisConfig::<Test> {
@@ -473,7 +473,7 @@ impl ExtBuilder {
 			keys: validators.iter().map(|x| (
 				*x,
 				*x,
-				SessionKeys { other: UintAuthorityId(*x) }
+				SessionKeys { other: UintAuthorityId(*x as u64) }
 			)).collect(),
 		}.assimilate_storage(&mut storage);
 
@@ -493,6 +493,11 @@ impl ExtBuilder {
 
 		ext
 	}
+	pub fn build_and_execute(self, test: impl FnOnce() -> ()) {
+		let mut ext = self.build();
+		ext.execute_with(test);
+		ext.execute_with(post_conditions);
+	}
 }
 
 pub type System = frame_system::Module<Test>;
@@ -501,61 +506,88 @@ pub type Session = pallet_session::Module<Test>;
 pub type Timestamp = pallet_timestamp::Module<Test>;
 pub type Staking = Module<Test>;
 
-pub fn active_era() -> EraIndex {
+fn post_conditions() {
+	check_nominators();
+	check_exposures();
+	check_ledgers();
+}
+
+pub(crate) fn active_era() -> EraIndex {
 	Staking::active_era().unwrap().index
 }
 
-pub fn check_exposure_all(era: EraIndex) {
-	ErasStakers::<Test>::iter_prefix(era).for_each(check_exposure)
+fn check_ledgers() {
+	// check the ledger of all stakers.
+	Bonded::<Test>::iter().for_each(|(_, ctrl)| assert_ledger_consistent(ctrl))
 }
 
-pub fn check_nominator_all(era: EraIndex) {
+fn check_exposures() {
+	// a check per validator to ensure the exposure struct is always sane.
+	let era = active_era();
+	ErasStakers::<Test>::iter_prefix(era).for_each(|expo| {
+		assert_eq!(
+			expo.total as u128,
+			expo.own as u128 + expo.others.iter().map(|e| e.value as u128).sum::<u128>(),
+			"wrong total exposure.",
+		);
+	})
+}
+
+fn check_nominators() {
+	// a check per nominator to ensure their entire stake is correctly distributed. Will only kick-
+	// in if the nomination was submitted before the current era.
+	let era = active_era();
 	<Nominators<Test>>::iter()
-		.for_each(|(acc, _)| check_nominator_exposure(era, acc));
+		.filter_map(|(nominator, nomination)|
+			if nomination.submitted_in > era {
+				Some(nominator)
+			} else {
+				None
+		})
+		.for_each(|nominator| {
+		// must be bonded.
+		assert_is_stash(nominator);
+		let mut sum = 0;
+		Session::validators()
+			.iter()
+			.map(|v| Staking::eras_stakers(era, v))
+			.for_each(|e| {
+				let individual = e.others.iter().filter(|e| e.who == nominator).collect::<Vec<_>>();
+				let len = individual.len();
+				match len {
+					0 => { /* not supporting this validator at all. */ },
+					1 => sum += individual[0].value,
+					_ => panic!("nominator cannot back a validator more than once."),
+				};
+			});
+
+		let nominator_stake = Staking::slashable_balance_of(&nominator);
+		// a nominator cannot over-spend.
+		assert!(
+			nominator_stake >= sum,
+			"failed: Nominator({}) stake({}) >= sum divided({})",
+			nominator,
+			nominator_stake,
+			sum,
+		);
+
+		let diff = nominator_stake - sum;
+		assert!(diff < 100);
+	});
 }
 
-/// Check for each selected validator: expo.total = Sum(expo.other) + expo.own
-pub fn check_exposure(expo: Exposure<AccountId, Balance>) {
-	assert_eq!(
-		expo.total as u128,
-		expo.own as u128 + expo.others.iter().map(|e| e.value as u128).sum::<u128>(),
-		"wrong total exposure",
-	);
-}
-
-/// Check that for each nominator: slashable_balance > sum(used_balance)
-/// Note: we might not consume all of a nominator's balance, but we MUST NOT over spend it.
-pub fn check_nominator_exposure(era: EraIndex, stash: AccountId) {
-	assert_is_stash(stash);
-	let mut sum = 0;
-	Session::validators()
-		.iter()
-		.map(|v| Staking::eras_stakers(era, v))
-		.for_each(|e| e.others.iter().filter(|i| i.who == stash).for_each(|i| sum += i.value));
-	let nominator_stake = Staking::slashable_balance_of(&stash);
-	// a nominator cannot over-spend.
-	assert!(
-		nominator_stake >= sum,
-		"failed: Nominator({}) stake({}) >= sum divided({})",
-		stash,
-		nominator_stake,
-		sum,
-	);
-}
-
-pub fn assert_is_stash(acc: AccountId) {
+fn assert_is_stash(acc: AccountId) {
 	assert!(Staking::bonded(&acc).is_some(), "Not a stash.");
 }
 
-pub fn assert_ledger_consistent(stash: AccountId) {
-	assert_is_stash(stash);
-	let ledger = Staking::ledger(stash - 1).unwrap();
-
+fn assert_ledger_consistent(ctrl: AccountId) {
+	// ensures ledger.total == ledger.active + sum(ledger.unlocking).
+	let ledger = Staking::ledger(ctrl).expect("Not a controller.");
 	let real_total: Balance = ledger.unlocking.iter().fold(ledger.active, |a, c| a + c.value);
 	assert_eq!(real_total, ledger.total);
 }
 
-pub fn bond_validator(stash: u64, ctrl: u64, val: u64) {
+pub(crate) fn bond_validator(stash: AccountId, ctrl: AccountId, val: Balance) {
 	let _ = Balances::make_free_balance_be(&stash, val);
 	let _ = Balances::make_free_balance_be(&ctrl, val);
 	assert_ok!(Staking::bond(
@@ -570,7 +602,12 @@ pub fn bond_validator(stash: u64, ctrl: u64, val: u64) {
 	));
 }
 
-pub fn bond_nominator(stash: u64, ctrl: u64, val: u64, target: Vec<u64>) {
+pub(crate) fn bond_nominator(
+	stash: AccountId,
+	ctrl: AccountId,
+	val: Balance,
+	target: Vec<AccountId>,
+) {
 	let _ = Balances::make_free_balance_be(&stash, val);
 	let _ = Balances::make_free_balance_be(&ctrl, val);
 	assert_ok!(Staking::bond(
@@ -582,7 +619,7 @@ pub fn bond_nominator(stash: u64, ctrl: u64, val: u64, target: Vec<u64>) {
 	assert_ok!(Staking::nominate(Origin::signed(ctrl), target));
 }
 
-pub fn run_to_block(n: BlockNumber) {
+pub(crate) fn run_to_block(n: BlockNumber) {
 	Staking::on_finalize(System::block_number());
 	for b in System::block_number() + 1..=n {
 		System::set_block_number(b);
@@ -594,12 +631,12 @@ pub fn run_to_block(n: BlockNumber) {
 	}
 }
 
-pub fn advance_session() {
+pub(crate) fn advance_session() {
 	let current_index = Session::current_index();
 	start_session(current_index + 1);
 }
 
-pub fn start_session(session_index: SessionIndex) {
+pub(crate) fn start_session(session_index: SessionIndex) {
 	assert_eq!(<Period as Get<BlockNumber>>::get(), 1, "start_session can only be used with session length 1.");
 	for i in Session::current_index()..session_index {
 		Staking::on_finalize(System::block_number());
@@ -612,12 +649,12 @@ pub fn start_session(session_index: SessionIndex) {
 	assert_eq!(Session::current_index(), session_index);
 }
 
-pub fn start_era(era_index: EraIndex) {
+pub(crate) fn start_era(era_index: EraIndex) {
 	start_session((era_index * <SessionsPerEra as Get<u32>>::get()).into());
 	assert_eq!(Staking::current_era().unwrap(), era_index);
 }
 
-pub fn current_total_payout_for_duration(duration: u64) -> u64 {
+pub(crate) fn current_total_payout_for_duration(duration: u64) -> Balance {
 	inflation::compute_total_payout(
 		<Test as Trait>::RewardCurve::get(),
 		Staking::eras_total_stake(Staking::active_era().unwrap().index),
@@ -626,7 +663,7 @@ pub fn current_total_payout_for_duration(duration: u64) -> u64 {
 	).0
 }
 
-pub fn reward_all_elected() {
+pub(crate) fn reward_all_elected() {
 	let rewards = <Test as Trait>::SessionInterface::validators()
 		.into_iter()
 		.map(|v| (v, 1));
@@ -634,14 +671,14 @@ pub fn reward_all_elected() {
 	<Module<Test>>::reward_by_ids(rewards)
 }
 
-pub fn validator_controllers() -> Vec<AccountId> {
+pub(crate) fn validator_controllers() -> Vec<AccountId> {
 	Session::validators()
 		.into_iter()
 		.map(|s| Staking::bonded(&s).expect("no controller for validator"))
 		.collect()
 }
 
-pub fn on_offence_in_era(
+pub(crate) fn on_offence_in_era(
 	offenders: &[OffenceDetails<
 		AccountId,
 		pallet_session::historical::IdentificationTuple<Test>,
@@ -671,7 +708,7 @@ pub fn on_offence_in_era(
 	}
 }
 
-pub fn on_offence_now(
+pub(crate) fn on_offence_now(
 	offenders: &[OffenceDetails<AccountId, pallet_session::historical::IdentificationTuple<Test>>],
 	slash_fraction: &[Perbill],
 ) {
@@ -681,7 +718,7 @@ pub fn on_offence_now(
 
 // winners will be chosen by simply their unweighted total backing stake. Nominator stake is
 // distributed evenly.
-pub fn horrible_phragmen_with_post_processing(
+pub(crate) fn horrible_phragmen_with_post_processing(
 	do_reduce: bool,
 ) -> (CompactAssignments, Vec<ValidatorIndex>, PhragmenScore) {
 	let mut backing_stake_of: BTreeMap<AccountId, Balance> = BTreeMap::new();
@@ -789,7 +826,7 @@ pub fn horrible_phragmen_with_post_processing(
 
 // Note: this should always logically reproduce [`offchain_election::prepare_submission`], yet we
 // cannot do it since we want to have `tweak` injected into the process.
-pub fn prepare_submission_with(
+pub(crate) fn prepare_submission_with(
 	do_reduce: bool,
 	tweak: impl FnOnce(&mut Vec<StakedAssignment<AccountId>>),
 ) -> (CompactAssignments, Vec<ValidatorIndex>, PhragmenScore) {
@@ -865,7 +902,7 @@ pub fn prepare_submission_with(
 }
 
 /// Make all validator and nominator request their payment
-pub fn make_all_reward_payment_before_migration(era: EraIndex) {
+pub(crate) fn make_all_reward_payment_before_migration(era: EraIndex) {
 	let validators_with_reward = ErasRewardPoints::<Test>::get(era).individual.keys()
 		.cloned()
 		.collect::<Vec<_>>();
@@ -897,7 +934,7 @@ pub fn make_all_reward_payment_before_migration(era: EraIndex) {
 }
 
 /// Make all validator and nominator request their payment
-pub fn make_all_reward_payment(era: EraIndex) {
+pub(crate) fn make_all_reward_payment(era: EraIndex) {
 	let validators_with_reward = ErasRewardPoints::<Test>::get(era).individual.keys()
 		.cloned()
 		.collect::<Vec<_>>();
diff --git a/substrate/frame/staking/src/tests.rs b/substrate/frame/staking/src/tests.rs
index 75c4edae22..837b085d68 100644
--- a/substrate/frame/staking/src/tests.rs
+++ b/substrate/frame/staking/src/tests.rs
@@ -33,7 +33,7 @@ use crate::Store;
 #[test]
 fn force_unstake_works() {
 	// Verifies initial conditions of mock
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// Account 11 is stashed and locked, and account 10 is the controller
 		assert_eq!(Staking::bonded(&11), Some(10));
 		// Cant transfer
@@ -55,7 +55,7 @@ fn force_unstake_works() {
 #[test]
 fn basic_setup_works() {
 	// Verifies initial conditions of mock
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// Account 11 is stashed and locked, and account 10 is the controller
 		assert_eq!(Staking::bonded(&11), Some(10));
 		// Account 21 is stashed and locked, and account 20 is the controller
@@ -77,7 +77,7 @@ fn basic_setup_works() {
 		assert_eq!(Staking::ledger(&1), None);
 
 		// ValidatorPrefs are default
-		assert_eq!(<Validators<Test>>::iter().collect::<Vec<_>>(), vec![
+		assert_eq_uvec!(<Validators<Test>>::iter().collect::<Vec<_>>(), vec![
 			(31, ValidatorPrefs::default()),
 			(21, ValidatorPrefs::default()),
 			(11, ValidatorPrefs::default())
@@ -105,7 +105,8 @@ fn basic_setup_works() {
 				others: vec![ IndividualExposure { who: 101, value: 375 }]
 			},
 		);
-		// initial slot_stake
+
+		// initial total stake = 1125 + 1375
 		assert_eq!(Staking::eras_total_stake(Staking::active_era().unwrap().index), 2500);
 
 
@@ -121,16 +122,12 @@ fn basic_setup_works() {
 
 		// New era is not being forced
 		assert_eq!(Staking::force_era(), Forcing::NotForcing);
-
-		// All exposures must be correct.
-		check_exposure_all(Staking::active_era().unwrap().index);
-		check_nominator_all(Staking::active_era().unwrap().index);
 	});
 }
 
 #[test]
 fn change_controller_works() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_eq!(Staking::bonded(&11), Some(10));
 
 		assert!(Session::validators().contains(&11));
@@ -156,7 +153,7 @@ fn rewards_should_work() {
 	// * rewards get recorded per session
 	// * rewards get paid per Era
 	// * Check that nominators are also rewarded
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_11 = Balances::total_balance(&11);
 		let init_balance_20 = Balances::total_balance(&20);
@@ -346,8 +343,6 @@ fn less_than_needed_candidates_works() {
 				ErasStakers::<Test>::iter_prefix(Staking::active_era().unwrap().index)
 					.all(|exposure| exposure.others.is_empty())
 			);
-			check_exposure_all(Staking::active_era().unwrap().index);
-			check_nominator_all(Staking::active_era().unwrap().index);
 		});
 }
 
@@ -529,9 +524,6 @@ fn nominating_and_rewards_should_work() {
 				initial_balance + 5 * payout_for_20 / 11,
 				1,
 			);
-
-			check_exposure_all(Staking::active_era().unwrap().index);
-			check_nominator_all(Staking::active_era().unwrap().index);
 		});
 }
 
@@ -542,7 +534,7 @@ fn nominators_also_get_slashed() {
 	// 10 - is the controller of 11
 	// 11 - is the stash.
 	// 2 - is the nominator of 20, 10
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
 		assert_eq!(Staking::validator_count(), 2);
 
 		// Set payee to controller
@@ -589,8 +581,7 @@ fn nominators_also_get_slashed() {
 		// initial + first era reward + slash
 		assert_eq!(Balances::total_balance(&11), initial_balance - validator_slash);
 		assert_eq!(Balances::total_balance(&2), initial_balance - nominator_slash);
-		check_exposure_all(Staking::active_era().unwrap().index);
-		check_nominator_all(Staking::active_era().unwrap().index);
+
 		// Because slashing happened.
 		assert!(is_disabled(10));
 	});
@@ -602,7 +593,7 @@ fn double_staking_should_fail() {
 	// * an account already bonded as stash cannot be be stashed again.
 	// * an account already bonded as stash cannot nominate.
 	// * an account already bonded as controller can nominate.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		let arbitrary_value = 5;
 		// 2 = controller, 1 stashed => ok
 		assert_ok!(
@@ -625,7 +616,7 @@ fn double_staking_should_fail() {
 fn double_controlling_should_fail() {
 	// should test (in the same order):
 	// * an account already bonded as controller CANNOT be reused as the controller of another account.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		let arbitrary_value = 5;
 		// 2 = controller, 1 stashed => ok
 		assert_ok!(Staking::bond(
@@ -644,7 +635,7 @@ fn double_controlling_should_fail() {
 
 #[test]
 fn session_and_eras_work() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_eq!(Staking::active_era().unwrap().index, 0);
 		assert_eq!(Session::current_index(), 0);
 
@@ -682,7 +673,7 @@ fn session_and_eras_work() {
 
 #[test]
 fn forcing_new_era_works() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// normal flow of session.
 		assert_eq!(Staking::active_era().unwrap().index, 0);
 		start_session(0);
@@ -738,7 +729,7 @@ fn forcing_new_era_works() {
 #[test]
 fn cannot_transfer_staked_balance() {
 	// Tests that a stash account cannot transfer funds
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
 		// Confirm account 11 is stashed
 		assert_eq!(Staking::bonded(&11), Some(10));
 		// Confirm account 11 has some free balance
@@ -763,7 +754,7 @@ fn cannot_transfer_staked_balance_2() {
 	// Tests that a stash account cannot transfer funds
 	// Same test as above but with 20, and more accurate.
 	// 21 has 2000 free balance but 1000 at stake
-	ExtBuilder::default().nominate(false).fair(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).fair(true).build_and_execute(|| {
 		// Confirm account 21 is stashed
 		assert_eq!(Staking::bonded(&21), Some(20));
 		// Confirm account 21 has some free balance
@@ -782,7 +773,7 @@ fn cannot_transfer_staked_balance_2() {
 #[test]
 fn cannot_reserve_staked_balance() {
 	// Checks that a bonded account cannot reserve balance from free balance
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// Confirm account 11 is stashed
 		assert_eq!(Staking::bonded(&11), Some(10));
 		// Confirm account 11 has some free balance
@@ -805,7 +796,7 @@ fn cannot_reserve_staked_balance() {
 #[test]
 fn reward_destination_works() {
 	// Rewards go to the correct destination as determined in Payee
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
 		// Check that account 11 is a validator
 		assert!(Session::validators().contains(&11));
 		// Check the balance of the validator account
@@ -904,7 +895,7 @@ fn validator_payment_prefs_work() {
 	// Test that validator preferences are correctly honored
 	// Note: unstake threshold is being directly tested in slashing tests.
 	// This test will focus on validator payment.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		let commission = Perbill::from_percent(40);
 		<Validators<Test>>::insert(&11, ValidatorPrefs {
 			commission: commission.clone(),
@@ -935,9 +926,6 @@ fn validator_payment_prefs_work() {
 		let reward_of_100 = shared_cut * exposure_1.others[0].value / exposure_1.total;
 		assert_eq_error_rate!(Balances::total_balance(&10), balance_era_1_10 + reward_of_10, 2);
 		assert_eq_error_rate!(Balances::total_balance(&100), balance_era_1_100 + reward_of_100, 2);
-
-		check_exposure_all(Staking::active_era().unwrap().index);
-		check_nominator_all(Staking::active_era().unwrap().index);
 	});
 
 }
@@ -947,7 +935,7 @@ fn bond_extra_works() {
 	// Tests that extra `free_balance` in the stash can be added to stake
 	// NOTE: this tests only verifies `StakingLedger` for correct updates
 	// See `bond_extra_and_withdraw_unbonded_works` for more details and updates on `Exposure`.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// Check that account 10 is a validator
 		assert!(<Validators<Test>>::contains_key(11));
 		// Check that account 10 is bonded to account 11
@@ -976,7 +964,7 @@ fn bond_extra_works() {
 		}));
 
 		// Call the bond_extra function with a large number, should handle it
-		assert_ok!(Staking::bond_extra(Origin::signed(11), u64::max_value()));
+		assert_ok!(Staking::bond_extra(Origin::signed(11), Balance::max_value()));
 		// The full amount of the funds should now be in the total and active
 		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
 			stash: 11,
@@ -995,7 +983,7 @@ fn bond_extra_and_withdraw_unbonded_works() {
 	// * It can add extra funds to the bonded account.
 	// * it can unbond a portion of its funds from the stash account.
 	// * Once the unbonding period is done, it can actually take the funds out of the stash.
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
 		// Set payee to controller. avoids confusion
 		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
 
@@ -1081,7 +1069,7 @@ fn bond_extra_and_withdraw_unbonded_works() {
 
 #[test]
 fn too_many_unbond_calls_should_not_work() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// locked at era 0 until 3
 		for _ in 0..MAX_UNLOCKING_CHUNKS-1 {
 			assert_ok!(Staking::unbond(Origin::signed(10), 1));
@@ -1359,7 +1347,7 @@ fn rebond_is_fifo() {
 
 #[test]
 fn reward_to_stake_works() {
-	ExtBuilder::default().nominate(false).fair(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).fair(false).build_and_execute(|| {
 		// Confirm validator count is 2
 		assert_eq!(Staking::validator_count(), 2);
 		// Confirm account 10 and 20 are validators
@@ -1401,9 +1389,6 @@ fn reward_to_stake_works() {
 		// -- new infos
 		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, 1000 + total_payout_0 / 2);
 		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 69 + total_payout_0 / 2);
-
-		check_exposure_all(Staking::active_era().unwrap().index);
-		check_nominator_all(Staking::active_era().unwrap().index);
 	});
 }
 
@@ -1411,7 +1396,7 @@ fn reward_to_stake_works() {
 fn on_free_balance_zero_stash_removes_validator() {
 	// Tests that validator storage items are cleaned up when stash is empty
 	// Tests that storage items are untouched when controller is empty
-	ExtBuilder::default().existential_deposit(10).build().execute_with(|| {
+	ExtBuilder::default().existential_deposit(10).build_and_execute(|| {
 		// Check the balance of the validator account
 		assert_eq!(Balances::free_balance(10), 256);
 		// Check the balance of the stash account
@@ -1430,7 +1415,7 @@ fn on_free_balance_zero_stash_removes_validator() {
 		assert!(<Payee<Test>>::contains_key(&11));
 
 		// Reduce free_balance of controller to 0
-		let _ = Balances::slash(&10, u64::max_value());
+		let _ = Balances::slash(&10, Balance::max_value());
 
 		// Check the balance of the stash account has not been touched
 		assert_eq!(Balances::free_balance(11), 256000);
@@ -1444,7 +1429,7 @@ fn on_free_balance_zero_stash_removes_validator() {
 		assert!(<Payee<Test>>::contains_key(&11));
 
 		// Reduce free_balance of stash to 0
-		let _ = Balances::slash(&11, u64::max_value());
+		let _ = Balances::slash(&11, Balance::max_value());
 		// Check total balance of stash
 		assert_eq!(Balances::total_balance(&11), 0);
 
@@ -1464,7 +1449,7 @@ fn on_free_balance_zero_stash_removes_validator() {
 fn on_free_balance_zero_stash_removes_nominator() {
 	// Tests that nominator storage items are cleaned up when stash is empty
 	// Tests that storage items are untouched when controller is empty
-	ExtBuilder::default().existential_deposit(10).build().execute_with(|| {
+	ExtBuilder::default().existential_deposit(10).build_and_execute(|| {
 		// Make 10 a nominator
 		assert_ok!(Staking::nominate(Origin::signed(10), vec![20]));
 		// Check that account 10 is a nominator
@@ -1484,7 +1469,7 @@ fn on_free_balance_zero_stash_removes_nominator() {
 		assert!(<Payee<Test>>::contains_key(&11));
 
 		// Reduce free_balance of controller to 0
-		let _ = Balances::slash(&10, u64::max_value());
+		let _ = Balances::slash(&10, Balance::max_value());
 		// Check total balance of account 10
 		assert_eq!(Balances::total_balance(&10), 0);
 
@@ -1500,7 +1485,7 @@ fn on_free_balance_zero_stash_removes_nominator() {
 		assert!(<Payee<Test>>::contains_key(&11));
 
 		// Reduce free_balance of stash to 0
-		let _ = Balances::slash(&11, u64::max_value());
+		let _ = Balances::slash(&11, Balance::max_value());
 		// Check total balance of stash
 		assert_eq!(Balances::total_balance(&11), 0);
 
@@ -1520,7 +1505,7 @@ fn on_free_balance_zero_stash_removes_nominator() {
 #[test]
 fn switching_roles() {
 	// Test that it should be possible to switch between roles (nominator, validator, idle) with minimal overhead.
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
 		// Reset reward destination
 		for i in &[10, 20] { assert_ok!(Staking::set_payee(Origin::signed(*i), RewardDestination::Controller)); }
 
@@ -1557,15 +1542,12 @@ fn switching_roles() {
 		mock::start_era(2);
 
 		assert_eq_uvec!(validator_controllers(), vec![2, 20]);
-
-		check_exposure_all(Staking::active_era().unwrap().index);
-		check_nominator_all(Staking::active_era().unwrap().index);
 	});
 }
 
 #[test]
 fn wrong_vote_is_null() {
-	ExtBuilder::default().nominate(false).validator_pool(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(false).validator_pool(true).build_and_execute(|| {
 		assert_eq_uvec!(validator_controllers(), vec![40, 30]);
 
 		// put some money in account that we'll use.
@@ -1687,8 +1669,6 @@ fn bond_with_little_staked_value_bounded() {
 				Balances::free_balance(&10),
 				init_balance_10 + total_payout_0 / 3 + total_payout_1 / 3,
 			);
-			check_exposure_all(Staking::active_era().unwrap().index);
-			check_nominator_all(Staking::active_era().unwrap().index);
 		});
 }
 
@@ -1707,80 +1687,39 @@ fn new_era_elects_correct_number_of_validators() {
 			Session::on_initialize(System::block_number());
 
 			assert_eq!(validator_controllers().len(), 1);
-			check_exposure_all(Staking::active_era().unwrap().index);
-			check_nominator_all(Staking::active_era().unwrap().index);
 		})
 }
 
 #[test]
-fn phragmen_should_not_overflow_validators() {
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
+fn phragmen_should_not_overflow() {
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
+		// This is the maximum value that we can have as the outcome of CurrencyToVote.
+		type Votes = u64;
+
 		let _ = Staking::chill(Origin::signed(10));
 		let _ = Staking::chill(Origin::signed(20));
 
-		bond_validator(3, 2, u64::max_value());
-		bond_validator(5, 4, u64::max_value());
+		bond_validator(3, 2, Votes::max_value() as Balance);
+		bond_validator(5, 4, Votes::max_value() as Balance);
 
-		bond_nominator(7, 6, u64::max_value() / 2, vec![3, 5]);
-		bond_nominator(9, 8, u64::max_value() / 2, vec![3, 5]);
+		bond_nominator(7, 6, Votes::max_value() as Balance, vec![3, 5]);
+		bond_nominator(9, 8, Votes::max_value() as Balance, vec![3, 5]);
 
 		mock::start_era(1);
 
 		assert_eq_uvec!(validator_controllers(), vec![4, 2]);
 
-		// This test will fail this. Will saturate.
-		// check_exposure_all();
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 3).total, u64::max_value());
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 5).total, u64::max_value());
+		// We can safely convert back to values within [u64, u128].
+		assert!(Staking::eras_stakers(active_era(), 3).total > Votes::max_value() as Balance);
+		assert!(Staking::eras_stakers(active_era(), 5).total > Votes::max_value() as Balance);
 	})
 }
 
 #[test]
-fn phragmen_should_not_overflow_nominators() {
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
-		let _ = Staking::chill(Origin::signed(10));
-		let _ = Staking::chill(Origin::signed(20));
-
-		bond_validator(3, 2, u64::max_value() / 2);
-		bond_validator(5, 4, u64::max_value() / 2);
-
-		bond_nominator(7, 6, u64::max_value(), vec![3, 5]);
-		bond_nominator(9, 8, u64::max_value(), vec![3, 5]);
-
-		mock::start_era(1);
-
-		assert_eq_uvec!(validator_controllers(), vec![4, 2]);
-
-		// Saturate.
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 3).total, u64::max_value());
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 5).total, u64::max_value());
-	})
-}
-
-#[test]
-fn phragmen_should_not_overflow_ultimate() {
-	ExtBuilder::default().nominate(false).build().execute_with(|| {
-		bond_validator(3, 2, u64::max_value());
-		bond_validator(5, 4, u64::max_value());
-
-		bond_nominator(7, 6, u64::max_value(), vec![3, 5]);
-		bond_nominator(9, 8, u64::max_value(), vec![3, 5]);
-
-		mock::start_era(1);
-
-		assert_eq_uvec!(validator_controllers(), vec![4, 2]);
-
-		// Saturate.
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 3).total, u64::max_value());
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 5).total, u64::max_value());
-	})
-}
-
-#[test]
-fn reward_validator_slashing_validator_doesnt_overflow() {
-	ExtBuilder::default().build().execute_with(|| {
-		let stake = u32::max_value() as u64 * 2;
-		let reward_slash = u32::max_value() as u64 * 2;
+fn reward_validator_slashing_validator_does_not_overflow() {
+	ExtBuilder::default().build_and_execute(|| {
+		let stake = u64::max_value() as Balance * 2;
+		let reward_slash = u64::max_value() as Balance * 2;
 
 		// Assert multiplication overflows in balance arithmetic.
 		assert!(stake.checked_mul(reward_slash).is_none());
@@ -1834,7 +1773,7 @@ fn reward_validator_slashing_validator_doesnt_overflow() {
 
 #[test]
 fn reward_from_authorship_event_handler_works() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		use pallet_authorship::EventHandler;
 
 		assert_eq!(<pallet_authorship::Module<Test>>::author(), 11);
@@ -1861,7 +1800,7 @@ fn reward_from_authorship_event_handler_works() {
 
 #[test]
 fn add_reward_points_fns_works() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// Not mandatory but must be coherent with rewards
 		assert_eq!(Session::validators(), vec![21, 11]);
 
@@ -1889,7 +1828,7 @@ fn add_reward_points_fns_works() {
 
 #[test]
 fn unbonded_balance_is_not_slashable() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// total amount staked is slashable.
 		assert_eq!(Staking::slashable_balance_of(&11), 1000);
 
@@ -1904,7 +1843,7 @@ fn unbonded_balance_is_not_slashable() {
 fn era_is_always_same_length() {
 	// This ensures that the sessions is always of the same length if there is no forcing no
 	// session changes.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		let session_per_era = <SessionsPerEra as Get<SessionIndex>>::get();
 
 		mock::start_era(1);
@@ -1927,7 +1866,7 @@ fn era_is_always_same_length() {
 
 #[test]
 fn offence_forces_new_era() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		on_offence_now(
 			&[OffenceDetails {
 				offender: (
@@ -1945,7 +1884,7 @@ fn offence_forces_new_era() {
 
 #[test]
 fn offence_ensures_new_era_without_clobbering() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_ok!(Staking::force_new_era_always(Origin::ROOT));
 		assert_eq!(Staking::force_era(), Forcing::ForceAlways);
 
@@ -1966,7 +1905,7 @@ fn offence_ensures_new_era_without_clobbering() {
 
 #[test]
 fn offence_deselects_validator_even_when_slash_is_zero() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert!(Session::validators().contains(&11));
 		assert!(<Validators<Test>>::contains_key(11));
 
@@ -1995,7 +1934,7 @@ fn offence_deselects_validator_even_when_slash_is_zero() {
 fn slashing_performed_according_exposure() {
 	// This test checks that slashing is performed according the exposure (or more precisely,
 	// historical exposure), not the current balance.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).own, 1000);
 
 		// Handle an offence with a historical exposure.
@@ -2021,7 +1960,7 @@ fn slashing_performed_according_exposure() {
 
 #[test]
 fn slash_in_old_span_does_not_deselect() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 
 		assert!(<Validators<Test>>::contains_key(11));
@@ -2087,7 +2026,6 @@ fn slash_in_old_span_does_not_deselect() {
 		assert_eq!(Staking::force_era(), Forcing::NotForcing);
 		assert!(<Validators<Test>>::contains_key(11));
 		assert!(Session::validators().contains(&11));
-		assert_ledger_consistent(11);
 	});
 }
 
@@ -2095,7 +2033,7 @@ fn slash_in_old_span_does_not_deselect() {
 fn reporters_receive_their_slice() {
 	// This test verifies that the reporters of the offence receive their slice from the slashed
 	// amount.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// The reporters' reward is calculated from the total exposure.
 		let initial_balance = 1125;
 
@@ -2118,7 +2056,6 @@ fn reporters_receive_their_slice() {
 		let reward_each = reward / 2; // split into two pieces.
 		assert_eq!(Balances::free_balance(1), 10 + reward_each);
 		assert_eq!(Balances::free_balance(2), 20 + reward_each);
-		assert_ledger_consistent(11);
 	});
 }
 
@@ -2126,7 +2063,7 @@ fn reporters_receive_their_slice() {
 fn subsequent_reports_in_same_span_pay_out_less() {
 	// This test verifies that the reporters of the offence receive their slice from the slashed
 	// amount, but less and less if they submit multiple reports in one span.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		// The reporters' reward is calculated from the total exposure.
 		let initial_balance = 1125;
 
@@ -2165,14 +2102,13 @@ fn subsequent_reports_in_same_span_pay_out_less() {
 		// 50% * (10% * (initial_balance / 2) - prior_payout)
 		let reward = ((initial_balance / 20) - prior_payout) / 2;
 		assert_eq!(Balances::free_balance(1), 10 + prior_payout + reward);
-		assert_ledger_consistent(11);
 	});
 }
 
 #[test]
 fn invulnerables_are_not_slashed() {
 	// For invulnerable validators no slashing is performed.
-	ExtBuilder::default().invulnerables(vec![11]).build().execute_with(|| {
+	ExtBuilder::default().invulnerables(vec![11]).build_and_execute(|| {
 		assert_eq!(Balances::free_balance(11), 1000);
 		assert_eq!(Balances::free_balance(21), 2000);
 
@@ -2208,15 +2144,13 @@ fn invulnerables_are_not_slashed() {
 				initial_balance - (2 * other.value / 10),
 			);
 		}
-		assert_ledger_consistent(11);
-		assert_ledger_consistent(21);
 	});
 }
 
 #[test]
 fn dont_slash_if_fraction_is_zero() {
 	// Don't slash if the fraction is zero.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_eq!(Balances::free_balance(11), 1000);
 
 		on_offence_now(
@@ -2233,8 +2167,6 @@ fn dont_slash_if_fraction_is_zero() {
 		// The validator hasn't been slashed. The new era is not forced.
 		assert_eq!(Balances::free_balance(11), 1000);
 		assert_eq!(Staking::force_era(), Forcing::ForceNew);
-
-		assert_ledger_consistent(11);
 	});
 }
 
@@ -2242,7 +2174,7 @@ fn dont_slash_if_fraction_is_zero() {
 fn only_slash_for_max_in_era() {
 	// multiple slashes within one era are only applied if it is more than any previous slash in the
 	// same era.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		assert_eq!(Balances::free_balance(11), 1000);
 
 		on_offence_now(
@@ -2284,14 +2216,13 @@ fn only_slash_for_max_in_era() {
 
 		// The validator got slashed 10% more.
 		assert_eq!(Balances::free_balance(11), 400);
-		assert_ledger_consistent(11);
 	})
 }
 
 #[test]
 fn garbage_collection_after_slashing() {
 	// ensures that `SlashingSpans` and `SpanSlash` of an account is removed after reaping.
-	ExtBuilder::default().existential_deposit(2).build().execute_with(|| {
+	ExtBuilder::default().existential_deposit(2).build_and_execute(|| {
 		assert_eq!(Balances::free_balance(11), 256_000);
 
 		on_offence_now(
@@ -2335,7 +2266,7 @@ fn garbage_collection_after_slashing() {
 fn garbage_collection_on_window_pruning() {
 	// ensures that `ValidatorSlashInEra` and `NominatorSlashInEra` are cleared after
 	// `BondingDuration`.
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 
 		assert_eq!(Balances::free_balance(11), 1000);
@@ -2376,7 +2307,7 @@ fn garbage_collection_on_window_pruning() {
 
 #[test]
 fn slashing_nominators_by_span_max() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 		mock::start_era(2);
 		mock::start_era(3);
@@ -2474,7 +2405,7 @@ fn slashing_nominators_by_span_max() {
 
 #[test]
 fn slashes_are_summed_across_spans() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 		mock::start_era(2);
 		mock::start_era(3);
@@ -2532,7 +2463,7 @@ fn slashes_are_summed_across_spans() {
 
 #[test]
 fn deferred_slashes_are_deferred() {
-	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
+	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
 		mock::start_era(1);
 
 		assert_eq!(Balances::free_balance(11), 1000);
@@ -2575,7 +2506,7 @@ fn deferred_slashes_are_deferred() {
 
 #[test]
 fn remove_deferred() {
-	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
+	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
 		mock::start_era(1);
 
 		assert_eq!(Balances::free_balance(11), 1000);
@@ -2651,7 +2582,7 @@ fn remove_deferred() {
 
 #[test]
 fn remove_multi_deferred() {
-	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
+	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
 		mock::start_era(1);
 
 		assert_eq!(Balances::free_balance(11), 1000);
@@ -2895,7 +2826,7 @@ mod offchain_phragmen {
 
 	#[test]
 	fn election_on_chain_fallback_works() {
-		ExtBuilder::default().build().execute_with(|| {
+		ExtBuilder::default().build_and_execute(|| {
 			start_session(1);
 			start_session(2);
 			assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
@@ -3814,7 +3745,7 @@ mod offchain_phragmen {
 
 #[test]
 fn slash_kicks_validators_not_nominators_and_disables_nominator_for_kicked_validator() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 		assert_eq_uvec!(Session::validators(), vec![11, 21]);
 
@@ -3881,7 +3812,7 @@ fn claim_reward_at_the_last_era_and_no_double_claim_and_invalid_claim() {
 	// * rewards get paid until history_depth for both validators and nominators
 	// * an invalid era to claim doesn't update last_reward
 	// * double claim of one era fails
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_100 = Balances::total_balance(&100);
 
@@ -3961,7 +3892,7 @@ fn claim_reward_at_the_last_era_and_no_double_claim_and_invalid_claim() {
 
 #[test]
 fn zero_slash_keeps_nominators() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(1);
 
 		assert_eq!(Balances::free_balance(11), 1000);
@@ -3999,7 +3930,7 @@ fn zero_slash_keeps_nominators() {
 
 #[test]
 fn six_session_delay() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		use pallet_session::SessionManager;
 
 		let val_set = Session::validators();
@@ -4053,11 +3984,11 @@ fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward(
 	// * If nominator nomination is below the $MaxNominatorRewardedPerValidator other nominator
 	//   then the nominator can't claim its reward
 	// * A nominator can't claim another nominator reward
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
-			let stash = 10_000 + i as u64;
-			let controller = 20_000 + i as u64;
-			let balance = 10_000 + i as u64;
+			let stash = 10_000 + i as AccountId;
+			let controller = 20_000 + i as AccountId;
+			let balance = 10_000 + i as Balance;
 			Balances::make_free_balance_be(&stash, balance);
 			assert_ok!(
 				Staking::bond(
@@ -4081,8 +4012,8 @@ fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward(
 
 		// Assert only nominators from 1 to Max are rewarded
 		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
-			let stash = 10_000 + i as u64;
-			let balance = 10_000 + i as u64;
+			let stash = 10_000 + i as AccountId;
+			let balance = 10_000 + i as Balance;
 			if stash == 10_000 {
 				assert!(Balances::free_balance(&stash) == balance);
 			} else {
@@ -4094,7 +4025,7 @@ fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward(
 
 #[test]
 fn set_history_depth_works() {
-	ExtBuilder::default().build().execute_with(|| {
+	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(10);
 		Staking::set_history_depth(Origin::ROOT, 20).unwrap();
 		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
@@ -4115,14 +4046,14 @@ fn set_history_depth_works() {
 fn test_payout_stakers() {
 	// Here we will test validator can set `max_nominators_payout` and it works.
 	// We also test that `payout_extra_nominators` works.
-	ExtBuilder::default().has_stakers(false).build().execute_with(|| {
+	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
 		let balance = 1000;
 		// Create three validators:
 		bond_validator(11, 10, balance); // Default(64)
 
 		// Create nominators, targeting stash of validators
 		for i in 0..100 {
-			bond_nominator(1000 + i, 100 + i, balance + i, vec![11]);
+			bond_nominator(1000 + i, 100 + i, balance + i as Balance, vec![11]);
 		}
 
 		mock::start_era(1);
@@ -4137,11 +4068,11 @@ fn test_payout_stakers() {
 		// Validator payout goes to controller.
 		assert!(Balances::free_balance(&10) > balance);
 		for i in 36..100 {
-			assert!(Balances::free_balance(&(100 + i)) > balance + i);
+			assert!(Balances::free_balance(&(100 + i)) > balance + i as Balance);
 		}
 		// The bottom 36 do not
 		for i in 0..36 {
-			assert_eq!(Balances::free_balance(&(100 + i)), balance + i);
+			assert_eq!(Balances::free_balance(&(100 + i)), balance + i as Balance);
 		}
 
 		// We track rewards in `claimed_rewards` vec
@@ -4195,14 +4126,14 @@ fn test_payout_stakers() {
 #[test]
 fn payout_stakers_handles_basic_errors() {
 	// Here we will test payouts handle all errors.
-	ExtBuilder::default().has_stakers(false).build().execute_with(|| {
+	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
 		// Same setup as the test above
 		let balance = 1000;
 		bond_validator(11, 10, balance); // Default(64)
 
 		// Create nominators, targeting stash
 		for i in 0..100 {
-			bond_nominator(1000 + i, 100 + i, balance + i, vec![11]);
+			bond_nominator(1000 + i, 100 + i, balance + i as Balance, vec![11]);
 		}
 
 		mock::start_era(1);
@@ -4239,7 +4170,7 @@ fn payout_stakers_handles_basic_errors() {
 
 #[test]
 fn bond_during_era_correctly_populates_claimed_rewards() {
-	ExtBuilder::default().has_stakers(false).build().execute_with(|| {
+	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
 		// Era = None
 		bond_validator(9, 8, 1000);
 		assert_eq!(
@@ -4361,7 +4292,7 @@ fn test_last_reward_migration() {
 	sp_io::TestExternalities::new(s).execute_with(|| {
 		HistoryDepth::put(84);
 		CurrentEra::put(99);
-		let nominations = Nominations::<u64> {
+		let nominations = Nominations::<AccountId> {
 			targets: vec![],
 			submitted_in: 0,
 			suppressed: false
@@ -4422,7 +4353,7 @@ fn rewards_should_work_before_migration() {
 	// * rewards get recorded per session
 	// * rewards get paid per Era
 	// * Check that nominators are also rewarded
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		MigrateEra::put(10);
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_11 = Balances::total_balance(&11);
@@ -4513,7 +4444,7 @@ fn migrate_era_should_work() {
 	// * rewards get recorded per session
 	// * rewards get paid per Era
 	// * Check that nominators are also rewarded
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		MigrateEra::put(1);
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_11 = Balances::total_balance(&11);
@@ -4601,7 +4532,7 @@ fn migrate_era_should_work() {
 #[test]
 #[should_panic]
 fn migrate_era_should_handle_error() {
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		MigrateEra::put(1);
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_11 = Balances::total_balance(&11);
@@ -4653,7 +4584,7 @@ fn migrate_era_should_handle_errors_2() {
 	// * rewards get recorded per session
 	// * rewards get paid per Era
 	// * Check that nominators are also rewarded
-	ExtBuilder::default().nominate(true).build().execute_with(|| {
+	ExtBuilder::default().nominate(true).build_and_execute(|| {
 		MigrateEra::put(1);
 		let init_balance_10 = Balances::total_balance(&10);
 		let init_balance_11 = Balances::total_balance(&11);