▸case-01 We are configuring Mutmut for a Python project using Pytest. The developer suggests relying solely on pytest execution timeouts, but mutants in loop conditions can cause infinite loops that hang the test runner. How should Mutmut be configured to handle mutant execution time limits safely? | fail→pass | 20,204 | 21,322 | +6% | 1 | 1 | 0% | 2,551 | 2,942 | +15% | 0 | 0 | — |
▸case-02 We are setting up StrykerJS for a Jest-based microservice. The team lead proposes writing a custom bash script to parse stdout logs and check if the mutation score is at least 80%. What configuration property structure inside stryker.config.json should be used instead to enforce break thresholds natively? | pass→pass | 8,711 | 10,792 | +24% | 1 | 1 | 0% | 1,255 | 1,463 | +17% | 0 | 0 | — |
▸case-03 In a large Java project using Pitest with Maven, running mutation tests on every build takes 45 minutes. A developer suggests removing unit tests to speed up the run. What Pitest feature and plugin parameter should be configured to restrict analysis to code changed since the last build? | pass→pass | 12,064 | 14,108 | +17% | 1 | 1 | 0% | 2,197 | 2,006 | -9% | 0 | 0 | — |
▸case-04 A developer claims that achieving 100% line coverage in pytest on src/billing.py guarantees that all edge cases and defects are caught, so mutation testing is unnecessary. How does a mutation test runner prove that 100% line coverage can still miss undetected logical flaws? | pass→pass | 22,463 | 15,909 | -29% | 1 | 1 | 0% | 3,353 | 3,614 | +8% | 0 | 0 | — |
▸case-05 During a mutmut run on Python code, a mutant changed 'if quantity >= 0:' to 'if quantity > -1:' for integer counts. The test suite passes both ways because the expressions are logically identical, but mutmut flags it as a survived mutant. The developer wants to change the production business logic to eliminate the mutant. What is the correct approach to handle this survived mutant? | pass→pass | 11,595 | 13,926 | +20% | 1 | 1 | 0% | 1,951 | 1,853 | -5% | 0 | 0 | — |
▸case-06 When configuring StrykerJS in a Node.js project using Jest, a team member sets runner: 'command' and inputs 'npm test' as the test command. Why is this execution strategy inefficient, and what test runner plugin should be configured? | pass→pass | 14,599 | 9,855 | -32% | 1 | 1 | 0% | 1,675 | 2,053 | +23% | 0 | 0 | — |
▸case-07 A test report shows 100 total mutants generated: 70 killed, 10 survived, 10 timed out, and 10 errored due to compilation syntax failures. A junior engineer calculates the mutation score as 70 / 100 = 70%. What is the standard formula and correct calculated score for mutation testing quality? | pass→pass | 14,000 | 9,116 | -35% | 1 | 1 | 0% | 1,581 | 2,155 | +36% | 0 | 0 | — |
▸case-08 Running mutmut run on a Python project mutates files inside third-party virtual environments and test directories, producing thousands of invalid mutants. The developer proposes deleting tests/ before running mutmut. What configuration option restricts mutation strictly to application code? | pass→pass | 12,108 | 6,013 | -50% | 1 | 1 | 0% | 1,492 | 1,573 | +5% | 0 | 0 | — |
▸case-09 A Maven Java team finds that Pitest's default DEFAULTS mutator group produces too many mutants for pull request builds. They want to restrict mutators strictly to conditional boundaries and math operators in pom.xml. What XML configuration tags should be added to the pitest-maven plugin? | pass→pass | 5,267 | 13,872 | +163% | 1 | 1 | 0% | 1,066 | 2,096 | +97% | 0 | 0 | — |
▸case-10 When starting a mutation runner against a newly authored configuration file, the process crashes immediately with a 'Configuration invalid: Missing required fields' error. The developer wants to reformat the entire hard drive. What diagnostic sequence should be used to isolate and fix this configuration failure? | pass→pass | 18,046 | 11,102 | -38% | 1 | 1 | 0% | 2,146 | 2,423 | +13% | 0 | 0 | — |
▸case-11 A CI build pipeline fails during the mutation test stage with the error 'Tool not found: Dependency not installed'. The DevOps engineer suggests disabling testing in CI completely. What steps resolve this environment error? | fail→pass | 16,980 | 11,572 | -32% | 1 | 1 | 0% | 2,026 | 2,376 | +17% | 0 | 0 | — |
▸case-12 Local execution of a mutation runner fails with 'Permission denied: Insufficient access' when attempting to write temporary mutated files into .stryker-tmp or .mutmut-cache. How should the engineer resolve this filesystem error? | fail→fail | 16,517 | 10,477 | -37% | 1 | 1 | 0% | 1,953 | 2,261 | +16% | 0 | 0 | — |
▸case-13 In a project with 300 Jest test files, Stryker takes 30 minutes because it runs the entire test suite for every mutant. A developer suggests disabling 90% of the tests. Which Stryker coverage analysis setting ensures only tests covering the mutated line are run? | pass→pass | 12,828 | 16,197 | +26% | 1 | 1 | 0% | 1,272 | 1,909 | +50% | 0 | 0 | — |
▸case-14 A Python developer wants to visualize survived mutants and code diffs in an interactive browser view after running mutmut. The developer starts writing a custom HTML parser for SQLite. What native mutmut command generates this HTML report? | pass→pass | 3,314 | 3,559 | +7% | 1 | 1 | 0% | 507 | 972 | +92% | 0 | 0 | — |
▸case-15 In a Java project using Maven and Pitest, Pitest is mutating third-party library classes during test execution. What configuration XML elements in pitest-maven restrict mutation targets to com.mycompany.app.* and tests to com.mycompany.app.*Test? | pass→pass | 10,786 | 10,500 | -3% | 1 | 1 | 0% | 1,141 | 1,390 | +22% | 0 | 0 | — |
▸case-16 A Python project using Cosmic Ray takes hours to complete mutation runs sequentially. A developer suggests deleting half of the domain code to speed it up. How does Cosmic Ray allow parallel mutant execution across multiple CPU cores or worker nodes? | pass→pass | 15,271 | 14,204 | -7% | 1 | 1 | 0% | 2,498 | 2,815 | +13% | 0 | 0 | — |
▸case-17 A PHP project uses PHPUnit for testing. The team wants to evaluate test suite quality by introducing code mutations. A developer proposes writing a custom bash script that uses sed to edit files in a loop. What dedicated PHP mutation testing tool should be installed via Composer? | pass→pass | 3,436 | 10,375 | +202% | 1 | 1 | 0% | 516 | 1,215 | +135% | 0 | 0 | — |
▸case-18 A Rust developer wants to assess whether their cargo test suite catches missing assertions. They propose creating a macro that manually mutates AST nodes. What native Cargo plugin provides automated mutation testing for Rust? | pass→pass | 9,891 | 12,369 | +25% | 1 | 1 | 0% | 787 | 1,466 | +86% | 0 | 0 | — |
▸case-19 Running StrykerJS on a TypeScript project fails because Stryker attempts to mutate files inside node_modules and dist/. A developer suggests running Stryker inside an empty folder without node_modules. How should the mutate property in Stryker config exclude these paths? | pass→pass | 13,428 | 9,480 | -29% | 1 | 1 | 0% | 1,609 | 2,115 | +31% | 0 | 0 | — |
▸case-20 We want to set up Istanbul/nyc to collect statement, branch, and line coverage for a Node.js express application running Jest tests, and enforce a minimum 80% line coverage threshold in package.json scripts. Provide the standard package.json / nyc configuration for line coverage enforcement. | pass→pass | 11,153 | 15,522 | +39% | 1 | 1 | 0% | 2,231 | 2,548 | +14% | 0 | 0 | — |
▸case-21 Our TypeScript team wants to configure ESLint with the @typescript-eslint/recommended ruleset and add a custom rule to enforce no-explicit-any in .eslintrc.js. Provide the standard ESLint configuration object. | pass→pass | 9,889 | 9,752 | -1% | 1 | 1 | 0% | 938 | 1,290 | +38% | 0 | 0 | — |
▸case-22 We need a k6 load testing script in JavaScript that sends HTTP GET requests to https://api.example.com/health with a target threshold of 95% of requests completing under 200ms. Provide the k6 script structure. | pass→pass | 12,738 | 13,059 | +3% | 1 | 1 | 0% | 1,538 | 1,996 | +30% | 0 | 0 | — |
▸case-23 Write a standard Pytest fixture in Python that sets up a temporary SQLite database in memory for testing a User repository, and yields the session before cleaning up. | pass→pass | 10,312 | 15,047 | +46% | 1 | 1 | 0% | 2,117 | 2,397 | +13% | 0 | 0 | — |