Мутационное тестирование – один из инструментов для повышение качества юнит тестов и, как следствие, всего продукта. В данном докладе будут описаны принципы, по которым работает мутационное тестирование, и инструменты, которые используются для проектов, написанных на JavaScript и TypeScript

1. Mutation Testing inMutation Testing in
JavaScriptJavaScript

2. Andrey KucherenkoAndrey Kucherenko

5. Mutation testing (or mutation
analysis or program mutation) is
used to design new software tests
and evaluate the quality of existing
software tests. Mutation testing
involves modifying a program in
small ways. Each mutated version
is called a mutant and tests detect
and reject mutants by causing the
behavior of the original version to
differ from the mutant. This is
called killingthe mutant. Test
suites are measured by the
percentage of mutants that they
kill. New tests can be designed to
kill additional mutants. Mutants are
based on well­defined mutation
operators that either mimic typical
programming errors (such as using
the wrong operator or variable name)
or force the creation of valuable
tests (such as dividing each
expression by zero). The purpose is
to help the tester develop effective
tests or locate weaknesses in the
[1]

6. Language Framework
Java PiTest
Ruby Mutant
PHP Humburg/Infection PHP
C# VisualMutator
Python Cosmic Ray/ MutPy
LLVM Mull

8. and TypeScript

9. npm install -g stryker-cli

10. stryker init

11. stryker run

14. export class CountService {
sum(a, b) {
return a + b;
}
divide(a, b) {
return a / b;
}
modulo(a, b) {
return a % b;
}
}
describe('Count Service', () => {
let sut;
beforeEach(() => {
sut = new CountService();
})
it('should sum numbers', () => {
expect(sut.sum(2, 2)).toEqual(4);
});
it('should get divided numbers', () => {
expect(sut.divide(2, 1)).toEqual(2);
})
});

16. mutantsmutants

22. LimitationsLimitations
Performance
Not all test frameworks
supported
Not all build tools
supported
Not all envs supported
Not all cases mutated

23. Questions?