How-to Guides

How to run Infection only for changed files

If you have thousands of files and too many tests, running Mutation Testing can take hours for your project. In this case, it’s very convenient to run it only for the modified files.

Assuming you are on a feature branch, and the main branch is master, we can do it as the following:

CHANGED_FILES=$(git diff origin/master --diff-filter=AM --name-only | grep src/ | paste -sd "," -);
INFECTION_FILTER="--filter=${CHANGED_FILES} --ignore-msi-with-no-mutations";

infection --threads=4 $INFECTION_FILTER

The --diff-filter=AM returns only added and modified files, because we are not going to use removed ones.

The --ignore-msi-with-no-mutations option tells Infection to not error on min MSI when we have 0 mutations.

Example for Travis CI:

- stage: Mutation Testing
- |
if [[ "${TRAVIS_PULL_REQUEST}" == "false" ]]; then
git remote set-branches --add origin $TRAVIS_BRANCH;
git fetch;
CHANGED_FILES=$(git diff origin/$TRAVIS_BRANCH --diff-filter=AM --name-only | grep src/ | paste -sd "," -);
INFECTION_FILTER="--filter=${CHANGED_FILES} --ignore-msi-with-no-mutations";


infection --threads=4 --log-verbosity=none $INFECTION_FILTER

For each job, Travis CI fetches only tested branch:

git clone --depth=50 --branch=feature/branch

That’s why we need to fetch $TRAVIS_BRANCH as well to make a git diff possible. Otherwise, you will get an error:

fatal: ambiguous argument 'origin/master': unknown revision or path not in the working tree.

How to disable Mutators and profiles

Disable Mutator

Mutators can be disabled in a config file - infection.json.. Let’s say you don’t want to mutate + to -. In order to disable this Mutator, the following config can be used:

"mutators": {
"@default": true,
"Plus": false

The full list of Mutator names can be found here.

In this example, we explicitly enable all Mutators from @default profile and disable Plus Mutator.

Read about Profiles here

Disable Profile

To disable all Mutators that work with Regular Expressions, we should disable the whole @regex profile:

"mutators": {
"@default": true,
"@regex": false

Disable in particular class or method or line

Sometimes you may want to disable Mutator or Profile just for one particular method or class. It’s possible with ignore setting of Mutators and Profiles with the following syntax:

"mutators": {
"@default": true,
"@regex": {
"ignore": [
"Minus": {
"ignore": [

Want to ignore the whole class? App\Controller\User

All classes in the namespace: App\Api\*

All classes Product in any namespace: App\*\Product

Method of the class: App\Api\Product::productList

Method in all classes: App\Api\*::productList

Method by pattern: App\Api\Product::pr?duc?List

Line of the code: App\Api\Product::product::33

Internally, all patterns are passed to fnmatch() PHP function. Please read its documentation to better understand how it works.