StorageReadable unit tests (#154)

Foundry unit tests for StorageReadable contract.

Closes #146.

Author: kamuik16

test/reader/StorageReadable.spec.ts

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+pragma solidity >=0.7.6 <0.9.0;
+pragma abicoder v2;
+
+import {Test} from "forge-std/Test.sol";
+import {StorageAccessibleWrapper} from "src/contracts/test/vendor/StorageAccessibleWrapper.sol";
+
+contract StorageReadableTest is Test {
+    StorageAccessibleWrapper instance;
+
+    function setUp() public {
+        instance = new StorageAccessibleWrapper();
+    }
+
+    function test_can_read_statically_sized_words() public {
+        instance.setFoo(42);
+        bytes memory actualBytes = instance.getStorageAt(instance.SLOT_FOO(), 1);
+        bytes memory expectedBytes = abi.encode(42);
+        assertEq(actualBytes, expectedBytes);
+    }
+
+    function test_can_read_fields_that_are_packed_into_single_storage_slot() public {
+        instance.setBar(7);
+        instance.setBam(13);
+        bytes memory actualBytes = instance.getStorageAt(instance.SLOT_BAR(), 1);
+        bytes memory expectedBytes = abi.encodePacked(new bytes(8), uint64(13), uint128(7));
+        assertEq(actualBytes, expectedBytes);
+    }
+
+    function test_can_read_arrays_in_one_go() public {
+        uint8 slot = instance.SLOT_BAZ();
+        uint256[] memory arr = new uint256[](2);
+        arr[0] = 42;
+        arr[1] = 1337;
+        instance.setBaz(arr);
+        bytes memory data = instance.getStorageAt(slot, 1);
+        uint256 length = abi.decode(data, (uint256));
+        assertEq(length, 2);
+        bytes memory packed = instance.getStorageAt(uint256(keccak256(abi.encode(slot))), length);
+        (uint256 firstValue, uint256 secondValue) = abi.decode(packed, (uint256, uint256));
+        assertEq(firstValue, 42);
+        assertEq(secondValue, 1337);
+    }
+
+    function test_can_read_mappings() public {
+        instance.setQuxKeyValue(42, 69);
+        bytes memory data = instance.getStorageAt(uint256(keccak256(abi.encode([42, instance.SLOT_QUX()]))), 1);
+        uint256 value = abi.decode(data, (uint256));
+        assertEq(value, 69);
+    }
+
+    function test_can_read_structs() public {
+        instance.setFoobar(19, 21);
+        bytes memory packed = instance.getStorageAt(instance.SLOT_FOOBAR(), 10);
+        (uint256 firstValue, uint256 secondValue) = abi.decode(packed, (uint256, uint256));
+        assertEq(firstValue, 19);
+        assertEq(secondValue, 21);
+    }
+}