test: migrate issuance Hardhat tests to Forge with 100% coverage

Port all allocator, eligibility, and direct-allocation tests from
Hardhat/TypeScript to Forge/Solidity. Tests cover access control,
distribution accounting, target management, defensive checks,
interface compliance, interface ID stability, and operator functions.

Mock contracts placed in test/unit/mocks/ for shared use across
test suites. All 188 tests pass.

Author: RembrandtK

packages/issuance/test/unit/allocator/construction.t.sol

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.33;
+
+import { Initializable } from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
+import { TransparentUpgradeableProxy } from "@openzeppelin/contracts/proxy/transparent/TransparentUpgradeableProxy.sol";
+
+import { BaseUpgradeable } from "../../../contracts/common/BaseUpgradeable.sol";
+import { IssuanceAllocator } from "../../../contracts/allocate/IssuanceAllocator.sol";
+import { IssuanceAllocatorSharedTest } from "./shared.t.sol";
+
+/// @notice Construction and initialization tests for IssuanceAllocator.
+contract IssuanceAllocatorConstructionTest is IssuanceAllocatorSharedTest {
+    /* solhint-disable graph/func-name-mixedcase */
+
+    function test_Revert_ZeroGraphTokenAddress() public {
+        vm.expectRevert(BaseUpgradeable.GraphTokenCannotBeZeroAddress.selector);
+        new IssuanceAllocator(address(0));
+    }
+
+    function test_Revert_ZeroGovernorAddress() public {
+        IssuanceAllocator impl = new IssuanceAllocator(address(token));
+        bytes memory initData = abi.encodeCall(IssuanceAllocator.initialize, (address(0)));
+        vm.expectRevert(BaseUpgradeable.GovernorCannotBeZeroAddress.selector);
+        new TransparentUpgradeableProxy(address(impl), address(this), initData);
+    }
+
+    function test_Init_GovernorRoleSet() public view {
+        assertTrue(allocator.hasRole(GOVERNOR_ROLE, governor));
+    }
+
+    function test_Init_DefaultTargetCount() public view {
+        // Should have 1 target (the default at index 0)
+        assertEq(allocator.getTargetCount(), 1);
+    }
+
+    function test_Init_DefaultTargetIsZeroAddress() public view {
+        assertEq(allocator.getTargetAt(0), address(0));
+    }
+
+    function test_Init_IssuancePerBlockIsZero() public view {
+        assertEq(allocator.getIssuancePerBlock(), 0);
+    }
+
+    function test_Init_LastDistributionBlockIsCurrentBlock() public view {
+        assertEq(allocator.getDistributionState().lastDistributionBlock, block.number);
+    }
+
+    function test_Revert_DoubleInitialization() public {
+        vm.expectRevert(Initializable.InvalidInitialization.selector);
+        allocator.initialize(governor);
+    }
+
+    /* solhint-enable graph/func-name-mixedcase */
+}

packages/issuance/test/unit/allocator/defensiveChecks.t.sol

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.33;
+
+import { Test } from "forge-std/Test.sol";
+
+import { TransparentUpgradeableProxy } from "@openzeppelin/contracts/proxy/transparent/TransparentUpgradeableProxy.sol";
+
+import { IssuanceAllocator } from "../../../contracts/allocate/IssuanceAllocator.sol";
+import { IssuanceAllocatorTestHarness } from "../../../contracts/test/allocate/IssuanceAllocatorTestHarness.sol";
+import { MockGraphToken } from "../mocks/MockGraphToken.sol";
+
+/// @notice Tests for defensive checks in IssuanceAllocator internal functions.
+contract IssuanceAllocatorDefensiveChecksTest is Test {
+    /* solhint-disable graph/func-name-mixedcase */
+
+    IssuanceAllocatorTestHarness internal harness;
+
+    function setUp() public {
+        MockGraphToken token = new MockGraphToken();
+        IssuanceAllocatorTestHarness impl = new IssuanceAllocatorTestHarness(address(token));
+        bytes memory initData = abi.encodeCall(IssuanceAllocator.initialize, (address(this)));
+        TransparentUpgradeableProxy proxy = new TransparentUpgradeableProxy(address(impl), address(this), initData);
+        harness = IssuanceAllocatorTestHarness(address(proxy));
+    }
+
+    function test_DistributePendingProportionally_AllocatedRateZero() public {
+        // Defensive: allocatedRate == 0 should return early without reverting
+        harness.exposedDistributePendingProportionally(100, 0, 1000);
+    }
+
+    function test_DistributePendingProportionally_AvailableZero() public {
+        // Defensive: available == 0 should return early without reverting
+        harness.exposedDistributePendingProportionally(0, 100, 1000);
+    }
+
+    function test_DistributePendingProportionally_BothZero() public {
+        // Defensive: both == 0 should return early without reverting
+        harness.exposedDistributePendingProportionally(0, 0, 1000);
+    }
+
+    /* solhint-enable graph/func-name-mixedcase */
+}