diff --git a/test/unit/BPool/BPool_JoinswapPoolAmountOut.t.sol b/test/unit/BPool/BPool_JoinswapPoolAmountOut.t.sol
new file mode 100644
index 00000000..98c22e0d
--- /dev/null
+++ b/test/unit/BPool/BPool_JoinswapPoolAmountOut.t.sol
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.25;
+
+import {BPoolBase} from './BPoolBase.sol';
+import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
+
+import {BNum} from 'contracts/BNum.sol';
+import {IBPool} from 'interfaces/IBPool.sol';
+
+contract BPoolJoinswapPoolAmountOut is BPoolBase, BNum {
+  address public tokenIn;
+
+  // Valid scenario
+  uint256 public poolAmountOut = 1e18;
+  uint256 public tokenInWeight = 8e18;
+  uint256 public totalWeight = 10e18;
+  uint256 public tokenInBalance = 300e18;
+  // ((((INIT_POOL_SUPPLY+poolAmountOut)/INIT_POOL_SUPPLY)^(1/(tokenInWeight/totalWeight)))*tokenInBalance-tokenInBalance)/(1-((1-(tokenInWeight/totalWeight))*MIN_FEE))
+  // ((((100+1)/100)^(1/(8/10)))*300-300)/(1-((1-(8/10))*(10^-6)))
+  // 3.754676583174615979425132956656691
+  uint256 public maxTokenIn = 3.754676583181324836e18;
+
+  function setUp() public virtual override {
+    super.setUp();
+    tokenIn = tokens[0];
+    bPool.set__finalized(true);
+    // mint an initial amount of pool shares (expected to happen at _finalize)
+    bPool.call__mintPoolShare(INIT_POOL_SUPPLY);
+    bPool.set__tokens(_tokensToMemory());
+    bPool.set__totalWeight(totalWeight);
+    bPool.set__records(tokenIn, IBPool.Record({bound: true, index: 0, denorm: tokenInWeight}));
+    vm.mockCall(tokenIn, abi.encodePacked(IERC20.balanceOf.selector), abi.encode(uint256(tokenInBalance)));
+  }
+
+  function test_RevertWhen_ReentrancyLockIsSet() external {
+    bPool.call__setLock(_MUTEX_TAKEN);
+    // it should revert
+    vm.expectRevert(IBPool.BPool_Reentrancy.selector);
+    bPool.joinswapPoolAmountOut(tokenIn, poolAmountOut, maxTokenIn);
+  }
+
+  function test_RevertWhen_PoolIsNotFinalized() external {
+    bPool.call__setLock(_MUTEX_TAKEN);
+    // it should revert
+    vm.expectRevert(IBPool.BPool_Reentrancy.selector);
+    bPool.joinswapPoolAmountOut(tokenIn, poolAmountOut, maxTokenIn);
+  }
+
+  function test_RevertWhen_TokenInIsNotBound() external {
+    // it should revert
+    vm.expectRevert(IBPool.BPool_TokenNotBound.selector);
+    bPool.joinswapPoolAmountOut(makeAddr('unknown token'), poolAmountOut, maxTokenIn);
+  }
+
+  function test_RevertWhen_TokenAmountInExceedsMaxRatio() external {
+    // it should revert
+    vm.expectRevert(IBPool.BPool_TokenAmountInAboveMaxRatio.selector);
+    // growing pool supply by 50% -> user has to provide over half of the
+    // pool's tokenIn (198 in this case, consistent with weight=0.8), while
+    // MAX_IN_RATIO=0.5
+    bPool.joinswapPoolAmountOut(tokenIn, 50e18, type(uint256).max);
+  }
+
+  function test_RevertWhen_CalculatedTokenAmountInIsMoreThanExpected() external {
+    // it should revert
+    vm.expectRevert(IBPool.BPool_TokenAmountInAboveMaxAmountIn.selector);
+    bPool.joinswapPoolAmountOut(tokenIn, poolAmountOut, maxTokenIn - 1);
+  }
+
+  function test_WhenPreconditionsAreMet() external {
+    // it sets reentrancy lock
+    bPool.expectCall__setLock(_MUTEX_TAKEN);
+    // it queries token in balance
+    vm.expectCall(tokenIn, abi.encodeCall(IERC20.balanceOf, (address(bPool))));
+    // it calls _pullUnderlying for token in
+    bPool.mock_call__pullUnderlying(tokenIn, address(this), maxTokenIn);
+    bPool.expectCall__pullUnderlying(tokenIn, address(this), maxTokenIn);
+    // it mints the pool shares
+    bPool.expectCall__mintPoolShare(poolAmountOut);
+    // it sends pool shares to caller
+    bPool.expectCall__pushPoolShare(address(this), poolAmountOut);
+    // it emits LOG_CALL event
+    bytes memory _data =
+      abi.encodeWithSelector(IBPool.joinswapPoolAmountOut.selector, tokenIn, poolAmountOut, maxTokenIn);
+    vm.expectEmit();
+    emit IBPool.LOG_CALL(IBPool.joinswapPoolAmountOut.selector, address(this), _data);
+    // it emits LOG_JOIN event for token in
+    vm.expectEmit();
+    emit IBPool.LOG_JOIN(address(this), tokenIn, maxTokenIn);
+    bPool.joinswapPoolAmountOut(tokenIn, poolAmountOut, maxTokenIn);
+
+    // it clears the reentrancy lock
+    assertEq(_MUTEX_FREE, bPool.call__getLock());
+  }
+}
diff --git a/test/unit/BPool/BPool_JoinswapPoolAmountOut.tree b/test/unit/BPool/BPool_JoinswapPoolAmountOut.tree
new file mode 100644
index 00000000..ec19a013
--- /dev/null
+++ b/test/unit/BPool/BPool_JoinswapPoolAmountOut.tree
@@ -0,0 +1,20 @@
+BPool::JoinswapPoolAmountOut
+├── when reentrancy lock is set
+│   └── it should revert
+├── when pool is not finalized
+│   └── it should revert
+├── when token in is not bound
+│   └── it should revert
+├── when token amount in exceeds max ratio
+│   └── it should revert 
+├── when calculated token amount in is more than expected
+│   └── it should revert
+└── when preconditions are met
+    ├── it emits LOG_CALL event
+    ├── it sets the reentrancy lock
+    ├── it queries token in balance
+    ├── it emits LOG_JOIN event for token in
+    ├── it mints the pool shares
+    ├── it sends pool shares to caller
+    ├── it calls _pullUnderlying for token in
+    └── it clears the reentrancy lock