From 1cf7d5ed65953c953571d97a9434a8a4d770c61e Mon Sep 17 00:00:00 2001
From: thedavidmeister <thedavidmeister@gmail.com>
Date: Mon, 4 May 2026 20:11:51 +0400
Subject: [PATCH] test InsufficientFlowOutputs revert and boundary
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Pins the lower-bound guard that rejects flowOutputs < MIN_FLOW_SENTINELS
returned by the deployer. Two tests:

- Negative: any flowOutputs in [0, MIN_FLOW_SENTINELS) reverts with
  InsufficientFlowOutputs.
- Boundary: flowOutputs == MIN_FLOW_SENTINELS is accepted (lowest valid).

Mutation verified: inverting the check (`<` → `>=`) makes both tests
fail; reverting passes.

Closes #311 #321.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 test/src/concrete/Flow.construction.t.sol | 42 ++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/test/src/concrete/Flow.construction.t.sol b/test/src/concrete/Flow.construction.t.sol
index 03206941..070c4670 100644
--- a/test/src/concrete/Flow.construction.t.sol
+++ b/test/src/concrete/Flow.construction.t.sol
@@ -6,7 +6,8 @@ import {Vm} from "forge-std/Test.sol";
 
 import {EvaluableConfigV3} from "rain.interpreter.interface/interface/IInterpreterCallerV2.sol";
 import {FlowTest} from "test/abstract/FlowTest.sol";
-import {EmptyFlowConfig} from "src/error/ErrFlow.sol";
+import {EmptyFlowConfig, InsufficientFlowOutputs} from "src/error/ErrFlow.sol";
+import {MIN_FLOW_SENTINELS} from "src/interface/IFlowV5.sol";
 
 contract FlowConstructionTest is FlowTest {
     function testFlowConstructionEmptyConfigReverts() external {
@@ -16,6 +17,45 @@ contract FlowConstructionTest is FlowTest {
         I_CLONE_FACTORY.clone(impl, abi.encode(emptyConfig));
     }
 
+    /// Reverts with `InsufficientFlowOutputs` when the deployer reports a
+    /// `flowOutputs` byte below `MIN_FLOW_SENTINELS` (= 3). Pinning this
+    /// protects the lower-bound guard at `Flow.flowInit` against regression.
+    /// forge-config: default.fuzz.runs = 100
+    function testFlowConstructionRevertsOnInsufficientFlowOutputs(
+        address expression,
+        bytes memory bytecode,
+        uint256[] memory constants,
+        uint8 flowOutputs
+    ) external {
+        vm.assume(flowOutputs < uint8(MIN_FLOW_SENTINELS));
+        bytes memory io = abi.encodePacked(uint8(0), flowOutputs);
+        expressionDeployerDeployExpression2MockCall(expression, io);
+
+        EvaluableConfigV3[] memory flowConfig = new EvaluableConfigV3[](1);
+        flowConfig[0] = EvaluableConfigV3(DEPLOYER, bytecode, constants);
+
+        address impl = deployFlowImplementation();
+        vm.expectRevert(InsufficientFlowOutputs.selector);
+        I_CLONE_FACTORY.clone(impl, abi.encode(flowConfig));
+    }
+
+    /// `flowOutputs == MIN_FLOW_SENTINELS` is the lowest accepted value.
+    /// Pinning this boundary against regression complements the negative
+    /// test above.
+    function testFlowConstructionAcceptsFlowOutputsAtMin(
+        address expression,
+        bytes memory bytecode,
+        uint256[] memory constants
+    ) external {
+        bytes memory io = abi.encodePacked(uint8(0), uint8(MIN_FLOW_SENTINELS));
+        expressionDeployerDeployExpression2MockCall(expression, io);
+
+        EvaluableConfigV3[] memory flowConfig = new EvaluableConfigV3[](1);
+        flowConfig[0] = EvaluableConfigV3(DEPLOYER, bytecode, constants);
+
+        I_CLONE_FACTORY.clone(deployFlowImplementation(), abi.encode(flowConfig));
+    }
+
     function testFlowConstructionInitialize(address expression, bytes memory bytecode, uint256[] memory constants)
         external
     {