add LegacyMintableERC20 tests (#13049)

* add LegacyMintableERC20 tests

* fixes

packages/contracts-bedrock/test/legacy/LegacyMintableERC20.t.sol

+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.15;
+
+// Testing utilities
+import { CommonTest } from "test/setup/CommonTest.sol";
+
+import { LegacyMintableERC20 } from "src/legacy/LegacyMintableERC20.sol";
+import { ILegacyMintableERC20 } from "src/universal/interfaces/ILegacyMintableERC20.sol";
+
+contract LegacyMintableERC20_Test is CommonTest {
+    LegacyMintableERC20 legacyMintableERC20;
+
+    function setUp() public override {
+        super.setUp();
+
+        legacyMintableERC20 = new LegacyMintableERC20(address(l2StandardBridge), address(L1Token), "_L2Token_", "_L2T_");
+    }
+
+    /// @notice Tests that the constructor sets the correct values
+    function test_constructor_works() public view {
+        assertEq(legacyMintableERC20.l2Bridge(), address(l2StandardBridge));
+        assertEq(legacyMintableERC20.l1Token(), address(L1Token));
+        assertEq(legacyMintableERC20.name(), "_L2Token_");
+        assertEq(legacyMintableERC20.symbol(), "_L2T_");
+        assertEq(legacyMintableERC20.decimals(), 18);
+    }
+
+    /// @notice Tests that the contract supports the correct interfaces
+    function test_supportsInterface_works() public view {
+        assertEq(legacyMintableERC20.supportsInterface(bytes4(keccak256("supportsInterface(bytes4)"))), true);
+        assertEq(
+            legacyMintableERC20.supportsInterface(
+                ILegacyMintableERC20.l1Token.selector ^ ILegacyMintableERC20.mint.selector
+                    ^ ILegacyMintableERC20.burn.selector
+            ),
+            true
+        );
+    }
+
+    /// @notice Tests that the mint function works when called by the bridge
+    function test_mint_byBridge_succeeds() public {
+        vm.prank(address(l2StandardBridge));
+        legacyMintableERC20.mint(address(this), 1000);
+        assertEq(legacyMintableERC20.balanceOf(address(this)), 1000);
+    }
+
+    /// @notice Tests that the mint function fails when called by an address other than the bridge
+    function test_mint_byNonBridge_reverts() public {
+        vm.expectRevert(bytes("Only L2 Bridge can mint and burn"));
+        legacyMintableERC20.mint(address(this), 1000);
+    }
+
+    /// @notice Tests that the burn function works when called by the bridge
+    function test_burn_byBridge_succeeds() public {
+        vm.prank(address(l2StandardBridge));
+        legacyMintableERC20.mint(address(this), 1000);
+
+        vm.prank(address(l2StandardBridge));
+        legacyMintableERC20.burn(address(this), 1000);
+        assertEq(legacyMintableERC20.balanceOf(address(this)), 0);
+    }
+
+    /// @notice Tests that the burn function fails when called by an address other than the bridge
+    function test_burn_byNonBridge_reverts() public {
+        vm.expectRevert(bytes("Only L2 Bridge can mint and burn"));
+        legacyMintableERC20.burn(address(this), 1000);
+    }
+}