diff --git a/contracts/PoseidonHasher.sol b/contracts/PoseidonHasher.sol
index 8b441a9..2a7907c 100644
--- a/contracts/PoseidonHasher.sol
+++ b/contracts/PoseidonHasher.sol
@@ -6,8 +6,6 @@ pragma solidity 0.8.15;
 
 interface IPoseidonHasher {
     function hash(uint256 input) external pure returns (uint256 result);
-
-    function identity() external pure returns (uint256);
 }
 
 contract PoseidonHasher is IPoseidonHasher {
@@ -1014,14 +1012,4 @@ contract PoseidonHasher is IPoseidonHasher {
             result := s0
         }
     }
-
-    function identity() external pure override returns (uint256) {
-        return _identity();
-    }
-
-    // The hash of 0
-    function _identity() internal pure returns (uint256) {
-        return
-            0x2a09a9fd93c590c26b91effbb2499f07e8f7aa12e2b4940a3aed2411cb65e11c;
-    }
 }
diff --git a/test/RLN.t.sol b/test/RLN.t.sol
new file mode 100644
index 0000000..9c7a260
--- /dev/null
+++ b/test/RLN.t.sol
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.15;
+
+import "../contracts/PoseidonHasher.sol";
+import "../contracts/Rln.sol";
+import "forge-std/Test.sol";
+import "forge-std/console.sol";
+
+contract RLNTest is Test {
+    RLN public rln;
+
+    uint256 public constant MEMBERSHIP_DEPOSIT = 1000000000000000;
+    uint256 public constant DEPTH = 20;
+    uint256 public constant SET_SIZE = 1048576;
+
+    /// @dev Setup the testing environment.
+    function setUp() public {
+        PoseidonHasher poseidon = new PoseidonHasher();
+        rln = new RLN(MEMBERSHIP_DEPOSIT, DEPTH, address(poseidon));
+    }
+
+    /// @dev Ensure that you can hash a value.
+    function test__Constants() public {
+        assertEq(rln.MEMBERSHIP_DEPOSIT(), MEMBERSHIP_DEPOSIT);
+        assertEq(rln.DEPTH(), DEPTH);
+        assertEq(rln.SET_SIZE(), SET_SIZE);
+    }
+
+    function test__ValidRegistration(uint256 idCommitment) public {
+        rln.register{value: MEMBERSHIP_DEPOSIT}(idCommitment);
+        assertEq(rln.stakedAmounts(idCommitment), MEMBERSHIP_DEPOSIT);
+        assertEq(rln.members(idCommitment), true);
+    }
+
+    function test__InvalidRegistration__DuplicateCommitment(
+        uint256 idCommitment
+    ) public {
+        rln.register{value: MEMBERSHIP_DEPOSIT}(idCommitment);
+        assertEq(rln.stakedAmounts(idCommitment), MEMBERSHIP_DEPOSIT);
+        assertEq(rln.members(idCommitment), true);
+        vm.expectRevert(bytes("RLN, _register: member already registered"));
+        rln.register{value: MEMBERSHIP_DEPOSIT}(idCommitment);
+    }
+
+    function test__InvalidRegistration__InsufficientDeposit(
+        uint256 idCommitment
+    ) public {
+        vm.expectRevert(
+            bytes("RLN, register: membership deposit is not satisfied")
+        );
+        rln.register{value: MEMBERSHIP_DEPOSIT - 1}(idCommitment);
+    }
+
+    function test__InvalidRegistration__FullSet(
+        uint256 idCommitmentSeed
+    ) public {
+        vm.assume(idCommitmentSeed < 2 ** 255 - SET_SIZE);
+        RLN tempRln = new RLN(
+            MEMBERSHIP_DEPOSIT,
+            2,
+            address(rln.poseidonHasher())
+        );
+        uint256 setSize = tempRln.SET_SIZE();
+        for (uint256 i = 0; i < setSize; i++) {
+            tempRln.register{value: MEMBERSHIP_DEPOSIT}(idCommitmentSeed + i);
+        }
+        assertEq(tempRln.idCommitmentIndex(), 4);
+        vm.expectRevert(bytes("RLN, register: set is full"));
+        tempRln.register{value: MEMBERSHIP_DEPOSIT}(idCommitmentSeed + setSize);
+    }
+}