diff --git a/test/abstract/FlowTransferOperation.sol b/test/abstract/FlowTransferOperation.sol
index cd8edad5..8e68a954 100644
--- a/test/abstract/FlowTransferOperation.sol
+++ b/test/abstract/FlowTransferOperation.sol
@@ -32,6 +32,53 @@ abstract contract FlowTransferOperation is Test {
         return FlowTransferV1(new ERC20Transfer[](0), new ERC721Transfer[](0), new ERC1155Transfer[](0));
     }
 
+    /// Builds a `FlowTransferV1` whose first ERC20 transfer has an
+    /// unauthorized `from` (neither the flow contract nor the caller) and
+    /// whose second is a valid self-flow. Used to test the
+    /// `UnsupportedERC20Flow` revert path on a multi-transfer batch.
+    //forge-lint: disable-next-line(mixed-case-function)
+    function unauthorizedERC20Flow(address unauthorized, address authorized, address flow, uint256 amount)
+        internal
+        view
+        returns (FlowTransferV1 memory)
+    {
+        ERC20Transfer[] memory erc20Transfers = new ERC20Transfer[](2);
+        erc20Transfers[0] = ERC20Transfer({token: TOKEN_A, from: unauthorized, to: flow, amount: amount});
+        erc20Transfers[1] = ERC20Transfer({token: TOKEN_B, from: flow, to: authorized, amount: amount});
+        return FlowTransferV1(erc20Transfers, new ERC721Transfer[](0), new ERC1155Transfer[](0));
+    }
+
+    /// Same shape as `unauthorizedERC20Flow` but for ERC721.
+    //forge-lint: disable-next-line(mixed-case-function)
+    function unauthorizedERC721Flow(address unauthorized, address authorized, address flow, uint256 tokenId)
+        internal
+        view
+        returns (FlowTransferV1 memory)
+    {
+        ERC721Transfer[] memory erc721Transfers = new ERC721Transfer[](2);
+        erc721Transfers[0] = ERC721Transfer({token: TOKEN_A, from: unauthorized, to: flow, id: tokenId});
+        erc721Transfers[1] = ERC721Transfer({token: TOKEN_B, from: flow, to: authorized, id: tokenId});
+        return FlowTransferV1(new ERC20Transfer[](0), erc721Transfers, new ERC1155Transfer[](0));
+    }
+
+    /// Same shape as `unauthorizedERC20Flow` but for ERC1155.
+    //forge-lint: disable-next-line(mixed-case-function)
+    function unauthorizedERC1155Flow(
+        address unauthorized,
+        address authorized,
+        address flow,
+        uint256 outId,
+        uint256 outAmount,
+        uint256 inId,
+        uint256 inAmount
+    ) internal view returns (FlowTransferV1 memory) {
+        ERC1155Transfer[] memory erc1155Transfers = new ERC1155Transfer[](2);
+        erc1155Transfers[0] =
+            ERC1155Transfer({token: TOKEN_A, from: unauthorized, to: flow, id: outId, amount: outAmount});
+        erc1155Transfers[1] = ERC1155Transfer({token: TOKEN_B, from: flow, to: authorized, id: inId, amount: inAmount});
+        return FlowTransferV1(new ERC20Transfer[](0), new ERC721Transfer[](0), erc1155Transfers);
+    }
+
     //forge-lint: disable-next-line(mixed-case-function)
     function transferERC721ToERC1155(
         address addressA,
diff --git a/test/src/concrete/Flow.transfer.t.sol b/test/src/concrete/Flow.transfer.t.sol
index 462f15b5..f07ea6e6 100644
--- a/test/src/concrete/Flow.transfer.t.sol
+++ b/test/src/concrete/Flow.transfer.t.sol
@@ -188,15 +188,9 @@ contract FlowTransferTest is FlowTest {
         assumeEtchable(bob, address(flow));
 
         {
-            ERC20Transfer[] memory erc20Transfers = new ERC20Transfer[](2);
-            erc20Transfers[0] = ERC20Transfer({token: TOKEN_A, from: bob, to: address(flow), amount: erc20Amount});
-            erc20Transfers[1] = ERC20Transfer({token: TOKEN_B, from: address(flow), to: alice, amount: erc20Amount});
-
             uint256[] memory stack = LibStackGeneration.generateFlowStack(
-                Sentinel.unwrap(RAIN_FLOW_SENTINEL),
-                FlowTransferV1(erc20Transfers, new ERC721Transfer[](0), new ERC1155Transfer[](0))
+                Sentinel.unwrap(RAIN_FLOW_SENTINEL), unauthorizedERC20Flow(bob, alice, address(flow), erc20Amount)
             );
-
             interpreterEval2MockCall(stack, new uint256[](0));
         }
 
@@ -242,15 +236,9 @@ contract FlowTransferTest is FlowTest {
         assumeEtchable(bob, address(flow));
 
         {
-            ERC721Transfer[] memory erc721Transfers = new ERC721Transfer[](2);
-            erc721Transfers[0] = ERC721Transfer({token: TOKEN_A, from: bob, to: address(flow), id: erc721TokenId});
-            erc721Transfers[1] = ERC721Transfer({token: TOKEN_B, from: address(flow), to: alice, id: erc721TokenId});
-
             uint256[] memory stack = LibStackGeneration.generateFlowStack(
-                Sentinel.unwrap(RAIN_FLOW_SENTINEL),
-                FlowTransferV1(new ERC20Transfer[](0), erc721Transfers, new ERC1155Transfer[](0))
+                Sentinel.unwrap(RAIN_FLOW_SENTINEL), unauthorizedERC721Flow(bob, alice, address(flow), erc721TokenId)
             );
-
             interpreterEval2MockCall(stack, new uint256[](0));
         }
 
@@ -283,20 +271,12 @@ contract FlowTransferTest is FlowTest {
         assumeEtchable(bob, address(flow));
 
         {
-            ERC1155Transfer[] memory erc1155Transfers = new ERC1155Transfer[](2);
-            erc1155Transfers[0] = ERC1155Transfer({
-                token: TOKEN_A, from: bob, to: address(flow), id: erc1155OutTokenId, amount: erc1155OutAmount
-            });
-
-            erc1155Transfers[1] = ERC1155Transfer({
-                token: TOKEN_B, from: address(flow), to: alice, id: erc1155InTokenId, amount: erc1155InAmount
-            });
-
             uint256[] memory stack = LibStackGeneration.generateFlowStack(
                 Sentinel.unwrap(RAIN_FLOW_SENTINEL),
-                FlowTransferV1(new ERC20Transfer[](0), new ERC721Transfer[](0), erc1155Transfers)
+                unauthorizedERC1155Flow(
+                    bob, alice, address(flow), erc1155OutTokenId, erc1155OutAmount, erc1155InTokenId, erc1155InAmount
+                )
             );
-
             interpreterEval2MockCall(stack, new uint256[](0));
         }