diff --git a/src/lib.rs b/src/lib.rs
index 69883e53..cacd03a0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -226,6 +226,8 @@ impl StateResolution {
         _room_id: &RoomId,
         auth_event_ids: &[Vec<EventId>],
     ) -> Result<Vec<EventId>> {
+        use itertools::Itertools;
+
         let mut chains = vec![];
 
         for ids in auth_event_ids {
@@ -235,17 +237,15 @@ impl StateResolution {
             chains.push(chain);
         }
 
-        if let Some(chain) = chains.first() {
+        if let Some(chain) = chains.first().cloned() {
             let rest = chains.iter().skip(1).flatten().cloned().collect();
             let common = chain.intersection(&rest).collect::<Vec<_>>();
 
             Ok(chains
-                .iter()
+                .into_iter()
                 .flatten()
                 .filter(|id| !common.contains(&id))
-                .cloned()
-                .collect::<BTreeSet<_>>()
-                .into_iter()
+                .dedup()
                 .collect())
         } else {
             Ok(vec![])
diff --git a/src/room_version.rs b/src/room_version.rs
index 10e64639..a4c27087 100644
--- a/src/room_version.rs
+++ b/src/room_version.rs
@@ -38,18 +38,19 @@ pub struct RoomVersion {
     /// not sure
     pub enforce_key_validity: bool,
 
-    // bool: before MSC2261/MSC2432,
     /// `m.room.aliases` had special auth rules and redaction rules
     /// before room version 6.
+    ///
+    /// before MSC2261/MSC2432,
     pub special_case_aliases_auth: bool,
     /// Strictly enforce canonicaljson, do not allow:
     /// * Integers outside the range of [-2 ^ 53 + 1, 2 ^ 53 - 1]
     /// * Floats
     /// * NaN, Infinity, -Infinity
     pub strict_canonicaljson: bool,
-    // bool: MSC2209: Check 'notifications' key while verifying
-    // m.room.power_levels auth rules.
     /// Verify notifications key while checking m.room.power_levels.
+    ///
+    /// bool: MSC2209: Check 'notifications'
     pub limit_notifications_power_levels: bool,
     /// Extra rules when verifying redaction events.
     pub extra_redaction_checks: bool,
@@ -73,7 +74,7 @@ impl RoomVersion {
         })
     }
 
-    fn version_1() -> Self {
+    pub fn version_1() -> Self {
         Self {
             version: RoomVersionId::Version1,
             disposition: RoomDisposition::Stable,
@@ -87,7 +88,7 @@ impl RoomVersion {
         }
     }
 
-    fn version_2() -> Self {
+    pub fn version_2() -> Self {
         Self {
             version: RoomVersionId::Version2,
             disposition: RoomDisposition::Stable,
@@ -101,7 +102,7 @@ impl RoomVersion {
         }
     }
 
-    fn version_3() -> Self {
+    pub fn version_3() -> Self {
         Self {
             version: RoomVersionId::Version3,
             disposition: RoomDisposition::Stable,
@@ -115,7 +116,7 @@ impl RoomVersion {
         }
     }
 
-    fn version_4() -> Self {
+    pub fn version_4() -> Self {
         Self {
             version: RoomVersionId::Version4,
             disposition: RoomDisposition::Stable,
@@ -129,7 +130,7 @@ impl RoomVersion {
         }
     }
 
-    fn version_5() -> Self {
+    pub fn version_5() -> Self {
         Self {
             version: RoomVersionId::Version5,
             disposition: RoomDisposition::Stable,
@@ -143,7 +144,7 @@ impl RoomVersion {
         }
     }
 
-    fn version_6() -> Self {
+    pub fn version_6() -> Self {
         Self {
             version: RoomVersionId::Version6,
             disposition: RoomDisposition::Stable,
diff --git a/tests/event_sorting.rs b/tests/event_sorting.rs
index 88a79140..67270e52 100644
--- a/tests/event_sorting.rs
+++ b/tests/event_sorting.rs
@@ -1,6 +1,6 @@
 use std::collections::BTreeMap;
 
-use ruma::{events::EventType, EventId, RoomVersionId};
+use ruma::{events::EventType, EventId};
 use state_res::{is_power_event, room_version::RoomVersion, StateMap};
 
 mod utils;
@@ -46,7 +46,7 @@ fn test_event_sort() {
     // TODO we may be able to skip this since they are resolved according to spec
     let resolved_power = state_res::StateResolution::iterative_auth_check(
         &room_id(),
-        &RoomVersion::new(&RoomVersionId::Version6).unwrap(),
+        &RoomVersion::version_6(),
         &sorted_power_events,
         &BTreeMap::new(), // unconflicted events
         &mut events,
diff --git a/tests/utils.rs b/tests/utils.rs
index 499a23fb..d487749e 100644
--- a/tests/utils.rs
+++ b/tests/utils.rs
@@ -260,6 +260,7 @@ impl<E: Event> TestStore<E> {
         room_id: &RoomId,
         event_ids: Vec<Vec<EventId>>,
     ) -> Result<Vec<EventId>> {
+        use itertools::Itertools;
         let mut chains = vec![];
         for ids in event_ids {
             // TODO state store `auth_event_ids` returns self in the event ids list
@@ -271,17 +272,15 @@ impl<E: Event> TestStore<E> {
             chains.push(chain);
         }
 
-        if let Some(chain) = chains.first() {
+        if let Some(chain) = chains.first().cloned() {
             let rest = chains.iter().skip(1).flatten().cloned().collect();
             let common = chain.intersection(&rest).collect::<Vec<_>>();
 
             Ok(chains
-                .iter()
+                .into_iter()
                 .flatten()
                 .filter(|id| !common.contains(&id))
-                .cloned()
-                .collect::<BTreeSet<_>>()
-                .into_iter()
+                .dedup()
                 .collect())
         } else {
             Ok(vec![])