## Uniswap V2: Swap Exact Tokens For Tokens In this lesson, we'll explore the `swapExactTokensForTokens` function, which allows us to swap a specific amount of tokens for another token. We'll start by simulating a transaction from a user. In our test, we'll use the `vm.prank` function to impersonate the user. ```javascript vm.prank(user); ``` The user will call the `UniswapV2Router02` contract, which contains the `swapExactTokensForTokens` function. We'll then specify the function to be called and assign the returned array of `uint` values to a variable. ```javascript uint256[] memory amounts = router.swapExactTokensForTokens( amountIn, amountOutMin, path, user, block.timestamp ); ``` These `uint` values represent the amount of each token exchanged during the swap. We can console.log these values to visualize the intermediate steps of the swap: ```javascript console.log("WETH", amounts[0]); console.log("DAI", amounts[1]); console.log("MKR", amounts[2]); ``` Lastly, we'll assert that the user's balance of MKR is greater than or equal to the minimum output amount. ```javascript assertGe(mkr.balanceOf(user), amountOutMin, "MKR balance of user"); ``` In this test, we're simulating a swap of WETH to DAI and then from DAI to MKR. This test also demonstrates how to use the `swapExactTokensForTokens` function in a practical scenario. To execute this test, we need to run `forge` with the correct fork URL and path. ```bash forge test --fork-url $FORK_URL --match-path test/uniswap-v2/exercises/UniswapV2/swap.sol -vv ``` This will run the test on a mainnet fork and provide verbose logging. This concludes our introduction to the `swapExactTokensForTokens` function. In future lessons, we'll delve deeper into the function's workings and explore additional use cases.