# Testcase failed: BLPOP on string value

**URL:** <https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054>\
**Category:** Challenges\
**Tags:** challenge:redis\
**Created:** [April 18, 2026, 5:22am UTC](https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054 "2026-04-18T05:22:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![asli-nobita](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/asli-nobita/32/22277_2.png) [@asli-nobita](https://forum.codecrafters.io/u/asli-nobita)\
**Post date:** [April 18, 2026, 5:22am UTC](https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054/1 "2026-04-18T05:22:07Z")

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How should we handle it if a BLPOP operation is called on a key which stored a string value previously?  
The testcases are as follows:  
SET mango banana  
BLPOP mango 0.3  
Are we to assume the BLPOP operation changes the type of the value stored at key mango, to a list instead?

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**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [April 18, 2026, 10:26pm UTC](https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054/4 "2026-04-18T22:26:08Z")

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Hey @asli-nobita, looks like you’ve got past the stage #XJ7. Do you happen to remember what was wrong? Would love to see if we can improve the tester / instructions.

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<div class="post-metadata">

**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [April 27, 2026, 6:12am UTC](https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054/6 "2026-04-27T06:12:05Z")

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Closing this thread due to inactivity. If you still need assistance, feel free to reopen or start a new discussion!

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**Author:** ![system](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/3X/7/0/700657133935c15703e22c7c8870394f6e6dc27d.svg) [@system](https://forum.codecrafters.io/u/system)\
**Post date:** [May 2, 2026, 6:12am UTC](https://forum.codecrafters.io/t/testcase-failed-blpop-on-string-value/16054/7 "2026-05-02T06:12:38Z")

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Closed on May 2, 2026, 6:12am UTC

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