diff --git a/examples/simple/remappings.txt b/examples/simple/remappings.txt
index 887332d9..52880057 100644
--- a/examples/simple/remappings.txt
+++ b/examples/simple/remappings.txt
@@ -1 +1,2 @@
 multicaller/=src/multicaller/
+openzeppelin/=../../tests/lib/openzeppelin-contracts/contracts/
diff --git a/examples/tokens/ERC721/test/ERC721Test.sol b/examples/tokens/ERC721/test/ERC721Test.sol
index 83f77f20..9307920d 100644
--- a/examples/tokens/ERC721/test/ERC721Test.sol
+++ b/examples/tokens/ERC721/test/ERC721Test.sol
@@ -54,19 +54,23 @@ abstract contract ERC721Test is SymTest, Test {
     }
 
     function check_transferFrom(address caller, address from, address to, address other, uint256 tokenId, uint256 otherTokenId) public virtual {
+        // not realistic in practice
+        // and in particular msg.sender == address(0) disables auth for OpenZeppelin ERC721
+        vm.assume(caller != address(0));
+
         // consider other address
-        require(other != from);
-        require(other != to);
+        vm.assume(other != from);
+        vm.assume(other != to);
 
         // consider other token ids
-        require(otherTokenId != tokenId);
+        vm.assume(otherTokenId != tokenId);
 
         // record their current balance
         uint256 oldBalanceFrom   = IERC721(token).balanceOf(from);
         uint256 oldBalanceTo     = IERC721(token).balanceOf(to);
         uint256 oldBalanceOther  = IERC721(token).balanceOf(other);
 
-        // record their current owner 
+        // record their current owner
         address oldOwner = IERC721(token).ownerOf(tokenId);
         address oldOtherTokenOwner = IERC721(token).ownerOf(otherTokenId);
 
@@ -81,26 +85,26 @@ abstract contract ERC721Test is SymTest, Test {
         }
 
         // ensure requirements of transfer
-        assert(from == oldOwner);
-        assert(approved);
+        assertEq(from, oldOwner);
+        assertTrue(approved);
 
         // ensure the owner is updated correctly
-        assert(IERC721(token).ownerOf(tokenId) == to);
-        assert(IERC721(token).getApproved(tokenId) == address(0)); // ensure the approval is reset
+        assertEq(IERC721(token).ownerOf(tokenId), to);
+        assertEq(IERC721(token).getApproved(tokenId), address(0)); // ensure the approval is reset
 
         // ensure the other token's owner is unchanged
-        assert(IERC721(token).ownerOf(otherTokenId) == oldOtherTokenOwner);
+        assertEq(IERC721(token).ownerOf(otherTokenId), oldOtherTokenOwner);
 
         // balance update
         if (from != to) {
-            assert(IERC721(token).balanceOf(from) < oldBalanceFrom);
-            assert(IERC721(token).balanceOf(from) == oldBalanceFrom - 1);
-            assert(IERC721(token).balanceOf(to) > oldBalanceTo);
-            assert(IERC721(token).balanceOf(to) == oldBalanceTo + 1);
+            assertLt(IERC721(token).balanceOf(from), oldBalanceFrom);
+            assertEq(IERC721(token).balanceOf(from), oldBalanceFrom - 1);
+            assertGt(IERC721(token).balanceOf(to), oldBalanceTo);
+            assertEq(IERC721(token).balanceOf(to), oldBalanceTo + 1);
         } else {
-            assert(IERC721(token).balanceOf(from) == oldBalanceFrom);
-            assert(IERC721(token).balanceOf(to) == oldBalanceTo);
+            assertEq(IERC721(token).balanceOf(from), oldBalanceFrom);
+            assertEq(IERC721(token).balanceOf(to), oldBalanceTo);
         }
-        assert(IERC721(token).balanceOf(other) == oldBalanceOther);
+        assertEq(IERC721(token).balanceOf(other), oldBalanceOther);
     }
 }
diff --git a/examples/tokens/ERC721/test/OpenZeppelinERC721.t.sol b/examples/tokens/ERC721/test/OpenZeppelinERC721.t.sol
index d661dc37..7db0b742 100644
--- a/examples/tokens/ERC721/test/OpenZeppelinERC721.t.sol
+++ b/examples/tokens/ERC721/test/OpenZeppelinERC721.t.sol
@@ -28,14 +28,12 @@ contract OpenZeppelinERC721Test is ERC721Test {
         tokenIds[4] = 5;
 
         // account0: {token0, token1}, account1: {token2}, account2: {token3}
-        vm.prank(deployer);
+        vm.startPrank(deployer);
         token_.transferFrom(deployer, accounts[0], tokenIds[0]);
-        vm.prank(deployer);
         token_.transferFrom(deployer, accounts[0], tokenIds[1]);
-        vm.prank(deployer);
         token_.transferFrom(deployer, accounts[1], tokenIds[2]);
-        vm.prank(deployer);
         token_.transferFrom(deployer, accounts[2], tokenIds[3]);
+        vm.stopPrank();
 
         vm.prank(accounts[0]);
         token_.approve(accounts[2], tokenIds[0]);