Challenge Library
Coding Challenges
5,893 curated questions across every arena — browse by topic, then jump into a live 3-minute battle to put them to the test.
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5,893 challenges total
- Code AnalysisIntermediate
Password hashing choice
backendintermediate - Code AnalysisIntermediate
X-Frame-Options
backendintermediate - Code AnalysisIntermediate
Audit log entry
backendintermediate - Multiple ChoiceIntermediate
Unit Testing
backendintermediate - Multiple ChoiceIntermediate
Integration Testing
backendintermediate - Multiple ChoiceIntermediate
E2E Testing
backendintermediate - Multiple ChoiceIntermediate
Test Pyramid
backendintermediate - Multiple ChoiceIntermediate
Mocking
backendintermediate - Multiple ChoiceHard
Stub vs Mock
backendhard - Multiple ChoiceBeginner
Assertions
backendbeginner - Multiple ChoiceIntermediate
Test Coverage
backendintermediate - Multiple ChoiceIntermediate
TDD Cycle
backendintermediate - Multiple ChoiceIntermediate
API Testing
backendintermediate - Multiple ChoiceIntermediate
Fixtures
backendintermediate - Multiple ChoiceIntermediate
Snapshot Testing
backendintermediate - Multiple ChoiceIntermediate
Regression Testing
backendintermediate - Multiple ChoiceIntermediate
Smoke Tests
backendintermediate - Multiple ChoiceIntermediate
Isolation in Tests
backendintermediate - Code AnalysisBeginner
Unit test example
backendbeginner - Code AnalysisIntermediate
Mock function
backendintermediate - Code AnalysisIntermediate
Integration test scope
backendintermediate - Code AnalysisIntermediate
Coverage percentage
backendintermediate - Code AnalysisBeginner
Assertion failure
backendbeginner - Code AnalysisIntermediate
TDD red-green-refactor
backendintermediate - Code AnalysisIntermediate
Test isolation issue
backendintermediate - Code AnalysisHard
Trace: Signed Left Shift
canalysishard - Code AnalysisHard
Trace: char Sign
canalysishard - Code AnalysisIntermediate
Trace: Double Free
canalysisintermediate - Code AnalysisIntermediate
Trace: Format Mismatch
canalysisintermediate - Code AnalysisHard
Trace: Struct Size
canalysishard - Code AnalysisIntermediate
Trace: Unsigned Wrap
canalysisintermediate - Code AnalysisBeginner
Trace: Integer Division
canalysisbeginner - Code AnalysisBeginner
Trace: Array Index
canalysisbeginner - Code AnalysisBeginner
Trace: Array Access
canalysisbeginner - Code AnalysisBeginner
Trace: Bitwise AND
canalysisbeginner - Code AnalysisBeginner
Trace: Bitwise OR
canalysisbeginner - Code AnalysisBeginner
Trace: Left Shift
canalysisbeginner - Code AnalysisBeginner
Trace: Break
canalysisbeginner - Code AnalysisBeginner
Trace: Char Arithmetic
canalysisbeginner - Code AnalysisBeginner
Trace: Continue
canalysisbeginner - Code AnalysisBeginner
Trace: Integer Division — Negative
canalysisbeginner - Code AnalysisBeginner
Trace: Float Cast
canalysisbeginner - Code AnalysisBeginner
Trace: Float Division
canalysisbeginner - Code AnalysisBeginner
Trace: Mixed Types
canalysisbeginner - Code AnalysisBeginner
Trace: Float Multiply
canalysisbeginner - Code AnalysisBeginner
Trace: For Loop
canalysisbeginner - Code AnalysisBeginner
Trace: Increment in Printf
canalysisbeginner - Code AnalysisBeginner
Trace: Logical AND
canalysisbeginner - Code AnalysisBeginner
Trace: Modulo
canalysisbeginner - Code AnalysisBeginner
Trace: Unary Negation
canalysisbeginner - Code AnalysisBeginner
Trace: Parentheses
canalysisbeginner - Code AnalysisBeginner
Trace: Post-Increment
canalysisbeginner - Code AnalysisBeginner
Trace: Pre-Increment
canalysisbeginner - Code AnalysisBeginner
Trace: Operator Precedence
canalysisbeginner - Code AnalysisBeginner
Trace: Address Of (basic)
canalysisbeginner - Code AnalysisBeginner
Trace: Array as Pointer
canalysisbeginner - Code AnalysisBeginner
Trace: Pointer Index
canalysisbeginner - Code AnalysisBeginner
Trace: Null Pointer
canalysisbeginner - Code AnalysisBeginner
Trace: Sizeof Array
canalysisbeginner - Code AnalysisBeginner
Trace: Sizeof Int
canalysisbeginner
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