coverage : is a process of collecting all reports about our unit tests that display uncovered lines to be reviewed again. we use the following command.
npm test -- --coverage
The preceding command creates a coverage directory that contains all reports about your unit tests.
We can automate the coverage process to be done after each modification you do in the file.test.js by adding jest options for the package.json file as follows.
{
...
"jest": {
"collectCoverage": true, // coverage process iteratively.
"coverageReports": ['html'] // types of reports.
}
}Then we run the following command.
npm test