diff --git a/crates/driver/src/boundary/liquidity/uniswap/v3.rs b/crates/driver/src/boundary/liquidity/uniswap/v3.rs
index 60a2b2fc5f..859b76105d 100644
--- a/crates/driver/src/boundary/liquidity/uniswap/v3.rs
+++ b/crates/driver/src/boundary/liquidity/uniswap/v3.rs
@@ -13,7 +13,6 @@ use {
     anyhow::Context,
     contracts::{GPv2Settlement, UniswapV3SwapRouter},
     ethrpc::current_block::BlockRetrieving,
-    itertools::Itertools,
     shared::{
         http_solver::model::TokenAmount,
         interaction::Interaction,
@@ -92,16 +91,12 @@ pub fn to_interaction(
         TokenAmount::new(output.0.token.into(), output.0.amount),
     );
 
-    interaction
-        .encode()
-        .into_iter()
-        .map(|(target, value, call_data)| eth::Interaction {
-            target: eth::Address(target),
-            value: eth::Ether(value),
-            call_data: call_data.0.into(),
-        })
-        .exactly_one()
-        .unwrap()
+    let encoded = interaction.encode();
+    eth::Interaction {
+        target: eth::Address(encoded.0),
+        value: eth::Ether(encoded.1),
+        call_data: crate::util::Bytes(encoded.2 .0),
+    }
 }
 
 pub fn collector(
diff --git a/crates/shared/src/http_solver/model.rs b/crates/shared/src/http_solver/model.rs
index de59281fd6..843eae0c43 100644
--- a/crates/shared/src/http_solver/model.rs
+++ b/crates/shared/src/http_solver/model.rs
@@ -188,8 +188,8 @@ pub struct InteractionData {
 }
 
 impl Interaction for InteractionData {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![(self.target, self.value, Bytes(self.call_data.clone()))]
+    fn encode(&self) -> EncodedInteraction {
+        (self.target, self.value, Bytes(self.call_data.clone()))
     }
 }
 
diff --git a/crates/shared/src/interaction.rs b/crates/shared/src/interaction.rs
index ef5735fc40..e6431f6c31 100644
--- a/crates/shared/src/interaction.rs
+++ b/crates/shared/src/interaction.rs
@@ -10,11 +10,11 @@ pub trait Interaction: std::fmt::Debug + Send + Sync {
     // Write::write returns a result but we know we write to a vector in memory so
     // we know it will never fail. Then the question becomes whether
     // interactions should be allowed to fail encoding for other reasons.
-    fn encode(&self) -> Vec<EncodedInteraction>;
+    fn encode(&self) -> EncodedInteraction;
 }
 
 impl Interaction for Box<dyn Interaction> {
-    fn encode(&self) -> Vec<EncodedInteraction> {
+    fn encode(&self) -> EncodedInteraction {
         self.as_ref().encode()
     }
 }
@@ -26,14 +26,14 @@ pub type EncodedInteraction = (
 );
 
 impl Interaction for EncodedInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![self.clone()]
+    fn encode(&self) -> EncodedInteraction {
+        self.clone()
     }
 }
 
 impl Interaction for InteractionData {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![(self.target, self.value, Bytes(self.call_data.clone()))]
+    fn encode(&self) -> EncodedInteraction {
+        (self.target, self.value, Bytes(self.call_data.clone()))
     }
 }
 
diff --git a/crates/shared/src/oneinch_api.rs b/crates/shared/src/oneinch_api.rs
index ae40a7d2f8..782f5d480b 100644
--- a/crates/shared/src/oneinch_api.rs
+++ b/crates/shared/src/oneinch_api.rs
@@ -402,8 +402,8 @@ pub struct Swap {
 }
 
 impl Interaction for Swap {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![(self.tx.to, self.tx.value, Bytes(self.tx.data.clone()))]
+    fn encode(&self) -> EncodedInteraction {
+        (self.tx.to, self.tx.value, Bytes(self.tx.data.clone()))
     }
 }
 
diff --git a/crates/shared/src/paraswap_api.rs b/crates/shared/src/paraswap_api.rs
index b45e3d33c7..21181c61f4 100644
--- a/crates/shared/src/paraswap_api.rs
+++ b/crates/shared/src/paraswap_api.rs
@@ -385,8 +385,8 @@ pub struct TransactionBuilderResponse {
 }
 
 impl Interaction for TransactionBuilderResponse {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![(self.to, self.value, Bytes(self.data.clone()))]
+    fn encode(&self) -> EncodedInteraction {
+        (self.to, self.value, Bytes(self.data.clone()))
     }
 }
 
diff --git a/crates/shared/src/zeroex_api.rs b/crates/shared/src/zeroex_api.rs
index f8fa5225cd..90e0d75ea4 100644
--- a/crates/shared/src/zeroex_api.rs
+++ b/crates/shared/src/zeroex_api.rs
@@ -327,8 +327,8 @@ pub struct SwapResponse {
 }
 
 impl Interaction for SwapResponse {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![(self.to, self.value, Bytes(self.data.clone()))]
+    fn encode(&self) -> EncodedInteraction {
+        (self.to, self.value, Bytes(self.data.clone()))
     }
 }
 
diff --git a/crates/solver/src/interactions/allowances.rs b/crates/solver/src/interactions/allowances.rs
index d16089a16a..c8e73a7d51 100644
--- a/crates/solver/src/interactions/allowances.rs
+++ b/crates/solver/src/interactions/allowances.rs
@@ -115,7 +115,7 @@ pub struct Approval {
 }
 
 impl Interaction for Approval {
-    fn encode(&self) -> Vec<EncodedInteraction> {
+    fn encode(&self) -> EncodedInteraction {
         // Use a "dummy" contract - unfortunately `ethcontract` doesn't
         // allow you use the generated contract intances to encode
         // transaction data without a `Web3` instance. Hopefully, this
@@ -365,7 +365,7 @@ mod tests {
         let spender = H160([0x02; 20]);
         assert_eq!(
             Approval { token, spender }.encode(),
-            vec![(
+            (
                 token,
                 0.into(),
                 Bytes(
@@ -376,7 +376,7 @@ mod tests {
                     )
                     .unwrap()
                 )
-            )]
+            )
         );
     }
 
diff --git a/crates/solver/src/interactions/balancer_v2.rs b/crates/solver/src/interactions/balancer_v2.rs
index c97a746d86..abf6f2b4c1 100644
--- a/crates/solver/src/interactions/balancer_v2.rs
+++ b/crates/solver/src/interactions/balancer_v2.rs
@@ -51,8 +51,8 @@ impl BalancerSwapGivenOutInteraction {
 }
 
 impl Interaction for BalancerSwapGivenOutInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![self.encode_swap()]
+    fn encode(&self) -> EncodedInteraction {
+        self.encode_swap()
     }
 }
 
@@ -95,7 +95,7 @@ mod tests {
         // ```
         assert_eq!(
             interaction.encode(),
-            vec![(
+            (
                 vault.address(),
                 0.into(),
                 Bytes(
@@ -118,7 +118,7 @@ mod tests {
                     )
                     .unwrap()
                 ),
-            )]
+            )
         );
     }
 }
diff --git a/crates/solver/src/interactions/erc20.rs b/crates/solver/src/interactions/erc20.rs
index 26285f6b21..96dbd249e5 100644
--- a/crates/solver/src/interactions/erc20.rs
+++ b/crates/solver/src/interactions/erc20.rs
@@ -23,8 +23,8 @@ impl Erc20ApproveInteraction {
 }
 
 impl Interaction for Erc20ApproveInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![self.as_encoded()]
+    fn encode(&self) -> EncodedInteraction {
+        self.as_encoded()
     }
 }
 
diff --git a/crates/solver/src/interactions/uniswap_v2.rs b/crates/solver/src/interactions/uniswap_v2.rs
index f11f6760fa..8e08507107 100644
--- a/crates/solver/src/interactions/uniswap_v2.rs
+++ b/crates/solver/src/interactions/uniswap_v2.rs
@@ -16,8 +16,8 @@ pub struct UniswapInteraction {
 }
 
 impl Interaction for UniswapInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        vec![self.encode_swap()]
+    fn encode(&self) -> EncodedInteraction {
+        self.encode_swap()
     }
 }
 
@@ -68,13 +68,9 @@ mod tests {
             token_in,
             token_out: H160::from_low_u64_be(token_out as u64),
         };
-        let interactions = interaction.encode();
-
-        // Single interaction
-        assert_eq!(interactions.len(), 1);
+        let swap_call = interaction.encode();
 
         // Verify Swap
-        let swap_call = &interactions[0];
         assert_eq!(swap_call.0, router.address());
         let call = &swap_call.2 .0;
         let swap_signature = hex!("8803dbee");
diff --git a/crates/solver/src/interactions/uniswap_v3.rs b/crates/solver/src/interactions/uniswap_v3.rs
index 5313fe6ece..02d97a0690 100644
--- a/crates/solver/src/interactions/uniswap_v3.rs
+++ b/crates/solver/src/interactions/uniswap_v3.rs
@@ -24,7 +24,7 @@ pub struct ExactOutputSingleParams {
     pub sqrt_price_limit_x96: U256,
 }
 impl Interaction for UniswapV3Interaction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
+    fn encode(&self) -> EncodedInteraction {
         let method = self.router.exact_output_single((
             self.params.token_amount_in_max.token,
             self.params.token_amount_out.token,
@@ -36,7 +36,7 @@ impl Interaction for UniswapV3Interaction {
             self.params.sqrt_price_limit_x96,
         ));
         let calldata = method.tx.data.expect("no calldata").0;
-        vec![(self.router.address(), 0.into(), Bytes(calldata))]
+        (self.router.address(), 0.into(), Bytes(calldata))
     }
 }
 
@@ -81,13 +81,9 @@ mod tests {
                 sqrt_price_limit_x96: U256::zero(),
             },
         };
-        let interactions = interaction.encode();
-
-        // Single interaction
-        assert_eq!(interactions.len(), 1);
+        let swap_call = interaction.encode();
 
         // Verify Swap
-        let swap_call = &interactions[0];
         assert_eq!(swap_call.0, router.address());
         let call = &swap_call.2 .0;
         let swap_signature = hex!("db3e2198");
diff --git a/crates/solver/src/interactions/weth.rs b/crates/solver/src/interactions/weth.rs
index 40ed5e1518..921275f7aa 100644
--- a/crates/solver/src/interactions/weth.rs
+++ b/crates/solver/src/interactions/weth.rs
@@ -32,10 +32,10 @@ impl UnwrapWethInteraction {
 }
 
 impl Interaction for UnwrapWethInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
+    fn encode(&self) -> EncodedInteraction {
         let method = self.weth.withdraw(self.amount);
         let calldata = method.tx.data.expect("no calldata").0;
-        vec![(self.weth.address(), 0.into(), Bytes(calldata))]
+        (self.weth.address(), 0.into(), Bytes(calldata))
     }
 }
 
@@ -51,9 +51,8 @@ mod tests {
             weth: weth.clone(),
             amount,
         };
-        let encoded_interactions = interaction.encode();
+        let withdraw_call = interaction.encode();
 
-        let withdraw_call = &encoded_interactions[0];
         assert_eq!(withdraw_call.0, weth.address());
         assert_eq!(withdraw_call.1, U256::from(0));
         let call = &withdraw_call.2 .0;
diff --git a/crates/solver/src/interactions/zeroex.rs b/crates/solver/src/interactions/zeroex.rs
index 1c77e90652..b2345e2fdd 100644
--- a/crates/solver/src/interactions/zeroex.rs
+++ b/crates/solver/src/interactions/zeroex.rs
@@ -15,7 +15,7 @@ pub struct ZeroExInteraction {
 }
 
 impl Interaction for ZeroExInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
+    fn encode(&self) -> EncodedInteraction {
         let method = self.zeroex.fill_or_kill_limit_order(
             (
                 self.order.maker_token,
@@ -40,6 +40,6 @@ impl Interaction for ZeroExInteraction {
             self.taker_token_fill_amount,
         );
         let calldata = method.tx.data.expect("no calldata").0;
-        vec![(self.zeroex.address(), 0.into(), Bytes(calldata))]
+        (self.zeroex.address(), 0.into(), Bytes(calldata))
     }
 }
diff --git a/crates/solver/src/liquidity/balancer_v2.rs b/crates/solver/src/liquidity/balancer_v2.rs
index cf7df80f65..c56cefb504 100644
--- a/crates/solver/src/liquidity/balancer_v2.rs
+++ b/crates/solver/src/liquidity/balancer_v2.rs
@@ -515,8 +515,7 @@ mod tests {
                     user_data: Default::default(),
                 }
                 .encode(),
-            ]
-            .concat(),
+            ],
         );
     }
 }
diff --git a/crates/solver/src/liquidity/zeroex.rs b/crates/solver/src/liquidity/zeroex.rs
index c50fdfa10c..7458808591 100644
--- a/crates/solver/src/liquidity/zeroex.rs
+++ b/crates/solver/src/liquidity/zeroex.rs
@@ -387,8 +387,7 @@ pub mod tests {
                     zeroex
                 }
                 .encode(),
-            ]
-            .concat(),
+            ],
         );
     }
 
@@ -420,8 +419,7 @@ pub mod tests {
                 taker_token_fill_amount: 100,
                 zeroex
             }
-            .encode(),]
-            .concat(),
+            .encode()],
         );
     }
 }
diff --git a/crates/solver/src/settlement.rs b/crates/solver/src/settlement.rs
index 3df284f283..2cab9f37d9 100644
--- a/crates/solver/src/settlement.rs
+++ b/crates/solver/src/settlement.rs
@@ -213,19 +213,7 @@ impl Trade {
     }
 }
 
-#[cfg(test)]
-use shared::interaction::{EncodedInteraction, Interaction};
 use shared::{external_prices::ExternalPrices, http_solver::model::Score};
-#[cfg(test)]
-#[derive(Debug)]
-pub struct NoopInteraction;
-
-#[cfg(test)]
-impl Interaction for NoopInteraction {
-    fn encode(&self) -> Vec<EncodedInteraction> {
-        Vec::new()
-    }
-}
 
 #[derive(Debug, Clone, Default)]
 pub struct Settlement {
diff --git a/crates/solver/src/settlement/settlement_encoder.rs b/crates/solver/src/settlement/settlement_encoder.rs
index bb3f522b07..1ea38faaf1 100644
--- a/crates/solver/src/settlement/settlement_encoder.rs
+++ b/crates/solver/src/settlement/settlement_encoder.rs
@@ -583,7 +583,7 @@ impl SettlementEncoder {
             interactions: [
                 self.pre_interactions
                     .into_iter()
-                    .flat_map(|interaction| interaction.encode())
+                    .map(|interaction| interaction.encode())
                     .collect(),
                 iter::empty()
                     .chain(
@@ -601,13 +601,13 @@ impl SettlementEncoder {
                                     Some(interaction)
                                 }
                             })
-                            .flat_map(|interaction| interaction.encode()),
+                            .map(|interaction| interaction.encode()),
                     )
-                    .chain(self.unwraps.iter().flat_map(|unwrap| unwrap.encode()))
+                    .chain(self.unwraps.iter().map(|unwrap| unwrap.encode()))
                     .collect(),
                 self.post_interactions
                     .into_iter()
-                    .flat_map(|interaction| interaction.encode())
+                    .map(|interaction| interaction.encode())
                     .collect(),
             ],
         }
@@ -738,7 +738,6 @@ pub fn verify_executed_amount(order: &Order, executed: U256) -> Result<()> {
 pub mod tests {
     use {
         super::*,
-        crate::settlement::NoopInteraction,
         contracts::{dummy_contract, WETH9},
         ethcontract::Bytes,
         maplit::hashmap,
@@ -798,11 +797,11 @@ pub mod tests {
             encoder
                 .finish(InternalizationStrategy::SkipInternalizableInteraction)
                 .interactions[1],
-            UnwrapWethInteraction {
+            [UnwrapWethInteraction {
                 weth,
                 amount: 3.into(),
             }
-            .encode(),
+            .encode()],
         );
     }
 
@@ -927,7 +926,7 @@ pub mod tests {
             encoder
                 .finish(InternalizationStrategy::SkipInternalizableInteraction)
                 .interactions[1],
-            [interaction.encode(), unwrap.encode()].concat(),
+            [interaction.encode(), unwrap.encode()],
         );
     }
 
@@ -1031,7 +1030,7 @@ pub mod tests {
         encoder0
             .add_trade(order12.clone(), 11.into(), 0.into())
             .unwrap();
-        encoder0.append_to_execution_plan(Arc::new(NoopInteraction {}));
+        encoder0.append_to_execution_plan(Arc::new(TestInteraction));
         encoder0.add_unwrap(UnwrapWethInteraction {
             weth: weth.clone(),
             amount: 1.into(),
@@ -1060,7 +1059,7 @@ pub mod tests {
         encoder1
             .add_trade(order23.clone(), 11.into(), 0.into())
             .unwrap();
-        encoder1.append_to_execution_plan(Arc::new(NoopInteraction {}));
+        encoder1.append_to_execution_plan(Arc::new(TestInteraction));
         encoder1.add_unwrap(UnwrapWethInteraction {
             weth,
             amount: 2.into(),
@@ -1424,8 +1423,8 @@ pub mod tests {
     #[derive(Debug)]
     pub struct TestInteraction;
     impl Interaction for TestInteraction {
-        fn encode(&self) -> Vec<EncodedInteraction> {
-            vec![(H160::zero(), U256::zero(), Bytes::default())]
+        fn encode(&self) -> EncodedInteraction {
+            (H160::zero(), U256::zero(), Bytes::default())
         }
     }
 
diff --git a/crates/solver/src/settlement_submission/submitter/public_mempool_api.rs b/crates/solver/src/settlement_submission/submitter/public_mempool_api.rs
index 6e4a67a732..817498e379 100644
--- a/crates/solver/src/settlement_submission/submitter/public_mempool_api.rs
+++ b/crates/solver/src/settlement_submission/submitter/public_mempool_api.rs
@@ -211,7 +211,21 @@ pub async fn validate_submission_node(node: &Web3, expected_network_id: &String)
 }
 #[cfg(test)]
 mod tests {
-    use {super::*, crate::settlement::NoopInteraction, std::sync::Arc};
+    use {
+        super::*,
+        ethcontract::Bytes,
+        primitive_types::{H160, U256},
+        shared::interaction::{EncodedInteraction, Interaction},
+        std::sync::Arc,
+    };
+
+    #[derive(Debug)]
+    pub struct TestInteraction;
+    impl Interaction for TestInteraction {
+        fn encode(&self) -> EncodedInteraction {
+            (H160::zero(), U256::zero(), Bytes::default())
+        }
+    }
 
     #[test]
     fn submission_status_configuration() {
@@ -219,7 +233,7 @@ mod tests {
             let mut settlement = Settlement::new(Default::default());
             settlement
                 .encoder
-                .append_to_execution_plan(Arc::new(NoopInteraction));
+                .append_to_execution_plan(Arc::new(TestInteraction));
             assert_eq!(settlement.revertable(), Revertable::HighRisk);
             settlement
         };