Bugs Discovered 🐛: We've come across a UI bug that prevents the redemption of tokens. Additionally, we've identified an issue where Flashloans are being reverted without reason.If you are new to UniLend, please take a look at the introduction provided in the first article available here: <a href="https://www.buildbear.io/resources/guides-and-tutorials/QA_UniLend">https://www.buildbear.io/resources/guides-and-tutorials/QA_UniLend</a>Setting up Infrastructure for Testing:UniLendV2 is deployed on Sepolia Testnet and ZkEVM Testnet. However, testing solely on these networks raises some concerns:<ul style="list-style-type:disc;"><li>Time constraints: Waiting for a year to test results is impractical, and it may render the review irrelevant.</li><li>Limitations on changing Token Price: The ability to modify the Token Price is not available.</li></ul>Due to these limitations, using Sepolia Testnet or ZkEVM is not feasible.Is there an alternative? Yes, we could consider using local hardhat fork or anvil fork. Nevertheless, this approach requires impersonating accounts to obtain ERC20 Tokens and executing additional hacks to observe our transactions and their outcomes. To simplify the process, we utilized <a href="http://buildbear.io/">BuildBear.io</a> to create a Private Testnet based on the Sepolia Testnet.NOTE: As premium users of BuildBear, the <code>chainId</code> we receive matches the forked Testnet's chainID (e.g., the private Testnet we created on BuildBear with the custom name batman has <code>chainId 11155111</code>, as it is a fork of Sepolia Testnet).Set-up before the testing:&nbsp;Using our Private Testnet Faucet to mint USDT.<figure class="image"><img src="https://strapi.buildbear.io/uploads/Untitled_design_7_1_283e587a56_6cf3dad369.gif" alt="Untitled_design_7_1_283e587a56.gif"></figure><ul style="list-style-type:disc;"><li>Transaction 1: Lending 10,000 USDC into USDC/WETH</li></ul><figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_2023_08_18_T094437_589_d7cadb2961.png" alt="Untitled - 2023-08-18T094437.589.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_2023_08_18_T094437_589_d7cadb2961.png 130w,https://strapi.buildbear.io/uploads/small_Untitled_2023_08_18_T094437_589_d7cadb2961.png 417w," sizes="100vw"></figure>&nbsp;&nbsp;<ol><li>Transaction 2: Borrowing 4 WETH using the 10,000 USDC Lent position</li></ol><figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_2023_08_18_T095600_265_d560988155.png" alt="Untitled - 2023-08-18T095600.265.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_2023_08_18_T095600_265_d560988155.png 89w,https://strapi.buildbear.io/uploads/small_Untitled_2023_08_18_T095600_265_d560988155.png 286w,https://strapi.buildbear.io/uploads/medium_Untitled_2023_08_18_T095600_265_d560988155.png 429w," sizes="100vw"></figure>&nbsp;<ol><li>Transaction 3: Creating a New pool for Pizza and USDC assets.&nbsp; The user interface for creating a new pool hasn't been added yet, so we have utilized the BuildBear Explorer to interact directly with the contract. The pool is created from the function createPool in Core Contract and requires addresses of both assets.</li></ol><figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/Untitled_4_41d1c683dc.png" alt="Untitled 4.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_4_41d1c683dc.png 245w,https://strapi.buildbear.io/uploads/small_Untitled_4_41d1c683dc.png 500w,https://strapi.buildbear.io/uploads/medium_Untitled_4_41d1c683dc.png 750w," sizes="100vw"></figure>&nbsp;USDC address: <code>0x6f14C02Fc1F78322cFd7d707aB90f18baD3B54f5</code>&nbsp; Pizza address: <code>0xccFeC573D5a84eA688c3b1e99a7b10D4b6D153A3</code><figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_5_9edd81d7c8.png" alt="Untitled 5.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_5_9edd81d7c8.png 245w," sizes="100vw"></figure><ol><li>Transaction 4: Lending 1000 USDC and 1000 Pizza tokens in the Newly Created pool</li></ol>&nbsp;<figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_13_c4a0a4ba7a.png" alt="Untitled 13.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_13_c4a0a4ba7a.png 115w,https://strapi.buildbear.io/uploads/small_Untitled_13_c4a0a4ba7a.png 369w," sizes="100vw"></figure><figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_7_a6f0c5606c.png" alt="Untitled 7.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_7_a6f0c5606c.png 128w,https://strapi.buildbear.io/uploads/small_Untitled_7_a6f0c5606c.png 412w," sizes="100vw"></figure><ol><li>Transaction 5: Borrowing 500 Pizza tokens from USDC/pizza pool</li></ol><figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_8_edc407edbd.png" alt="Untitled 8.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_8_edc407edbd.png 89w,https://strapi.buildbear.io/uploads/small_Untitled_8_edc407edbd.png 286w,https://strapi.buildbear.io/uploads/medium_Untitled_8_edc407edbd.png 430w," sizes="100vw"></figure>Executing different scenariosIn order to facilitate this, it is crucial to have the following abilities:The ability to modify the price of assets.The ability to save the state of the Testnet at different points of testing. This eliminates the need to create multiple Testnets for executing different scenarios. To accomplish this, we have utilized the BuildBear utility tool, as demonstrated below, to create a snapshot of the Testnet at the required points.<figure class="image"><img src="https://strapi.buildbear.io/uploads/Untitled_design_8_1_e716fb252c_b58f41fb68.gif" alt="Untitled_design_8_1_e716fb252c.gif"></figure>Advancing the time for a year&nbsp;(Using the BuildBear utility tools we were able to Advance time by a year as shown below).<figure class="image"><img src="https://strapi.buildbear.io/uploads/image_b8f3a93ec4.gif" alt="image.gif"></figure>Case 1: The price of Assets Remains the same || The simplest of the testRepaying the 500 Pizza and 4 WETH tokens we have Borrowed Tokens with interest.<figure class="image image_resized" style="width:22.63%;"><img src="https://strapi.buildbear.io/uploads/Untitled_9_19031d5af1.png" alt="Untitled 9.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_9_19031d5af1.png 157w," sizes="100vw"></figure><figure class="image image_resized" style="width:22.48%;"><img src="https://strapi.buildbear.io/uploads/Untitled_10_429f82d156.png" alt="Untitled 10.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_10_429f82d156.png 155w," sizes="100vw"></figure>&nbsp;Redeeming USDC, and Pizza Tokens we received from our lending positions.<figure class="image image_resized" style="width:25%;"><img src="https://strapi.buildbear.io/uploads/Untitled_11_491f456e59.png" alt="Untitled 11.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_11_491f456e59.png 117w,https://strapi.buildbear.io/uploads/small_Untitled_11_491f456e59.png 374w," sizes="100vw"></figure>Discovered a Bug While Claiming Tokens:While in the process of redeeming the tokens, we encountered the following error. We promptly reported this issue to UniLend, and they identified it to be a frontend-issue.The error message is as follows:<code>Error: invalid BigNumber string (argument="value", value="-10000000137036236430941.05"</code><figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/Untitled_14_af5276b444.png" alt="Untitled 14.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_14_af5276b444.png 245w,https://strapi.buildbear.io/uploads/small_Untitled_14_af5276b444.png 500w,https://strapi.buildbear.io/uploads/medium_Untitled_14_af5276b444.png 750w,https://strapi.buildbear.io/uploads/large_Untitled_14_af5276b444.png 1000w," sizes="100vw"></figure>Status : As of August 15, 2023, Unilend's team has been notified about this issue and has acknowledged their intent to investigate it further.Utilizing Flashloans:The UnilendV2 flashloan feature facilitates smart contracts in accessing pool liquidity within a single transaction through uncollateralized borrowing, as long as the borrowed amount plus a fee is repaid.In our current implementation, we have opted for the standard template provided by Unilend.<figure class="image"><img src="https://strapi.buildbear.io/uploads/carbon_6_175615be60.svg" alt="carbon_(6).svg"></figure>The code can be found here: <a href="https://github.com/BuildBearLabs/Tutorials/tree/main/flashloan_Unilend">GitHub Link</a>To execute a successful Flashloan we have added the required tokens to the flash loan contract to cover the associated flash loan fee. Subsequently, proceed with the execution of the flash loan. However, during the execution of the FlashLoan, the transaction is getting reverted as shown below.<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/Untitled_2023_08_17_T141334_490_84da3a4a8c.png" alt="Untitled_-_2023-08-17T141334.490.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_2023_08_17_T141334_490_84da3a4a8c.png 245w,https://strapi.buildbear.io/uploads/small_Untitled_2023_08_17_T141334_490_84da3a4a8c.png 500w,https://strapi.buildbear.io/uploads/medium_Untitled_2023_08_17_T141334_490_84da3a4a8c.png 750w,https://strapi.buildbear.io/uploads/large_Untitled_2023_08_17_T141334_490_84da3a4a8c.png 1000w," sizes="100vw"></figure>We have escalated the issue to the UniLend team, and they are currently conducting an investigation to identify the root cause.Status : As of August 15, 2023, Unilend's team has been notified about this issue and has acknowledged their intent to investigate it further.Conclusion: Thanks to BuildBear's advanced features, we were able to fast-forward time and identify the UI issue during the token redemption process.Using BuildBear for your QAIf you are DeFi Web3 App and you are looking to either<ul style="list-style-type:disc;"><li>Create an internal QA Environment for your team, or</li><li>Creating a private testing environment for your community before releasing to the Mainnet, or</li></ul>Come talk to us at&nbsp;<a href="mailto:team@buildbear.io">team@buildbear.io</a>&nbsp;We can help you create your own, 100% customized testing environment, so that you can use it without any hassle.NOTE:&nbsp;Information in this article shouldn’t be taken as Finance Advice.Author: <a href="https://twitter.com/chandan1_">chandan</a>

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We've come across a UI bug that prevents the redemption of tokens. Additionally, we've identified an issue where Flashloans are being reverted without reason...

In-Depth Technical QA Dive into UniLendV2 || Reporting a Front-End Bug

BUILDBEAR // TUTORIALS

In-Depth Technical QA Dive into UniLendV2 || Reporting a Front-End Bug

Let’s get started then, Shall we?

Let’s get started then, Shall we?

Test DApps at Scale.