umassdgithub / mutation_testing

Mutation Testing

Using Stryker to generate mutants and test them

In this example, 2 basic JS functions are tested using the Jest unit testing library.

• bmi.js: which calculates the BMI by pounds, feet and inches
• gradeToLetter.js: Returns the corresponding letter for a grade.

The steps to run

• install nodejs
• install stryker using npm npm install -g stryker
• to install the dependencies, run: npm install
• to run the unit test (Jest), use: npm test
• to run the mutation generate using stryker and Jest : npx stryker run --reporters html

The last line generates an HTML file with the name of repoerters/mutation.html which contains the test results for the coverage and also Mutants.

Exercise

Getting to know the artifact:

Review the code provided for gradeToLetter.js and the provided gradeToLetter.test.js to test the functionality of the function.

Run the tests

Run the following command: npm test

Generate mutants

Run the following command: npx stryker run --reporters html

Open the report

Open the report in the browser: open reports/mutation/mutation.html

Find Survivors

Find the mutants that survived the mutation testing.

Use the report to improve the tests

Add test cases for the mutants that survived the mutation testing.

Redo the tests

Run the previous commands to execute the tests again. Check if there are any other mutants that survived the mutation testing.

Delivarable Checklist

• The new gradeToLetter.test.js file with new test cases. (50 Points)
• The new Stryker report mutation.html file. (50 Points)