Understanding Jest Coverage: Hide Files That Are Ignored
When working with Jest, a powerful JavaScript testing framework, you might come across scenarios where certain files are intentionally ignored from coverage reports. This can be due to various reasons, such as external dependencies, test files, or files that are not part of the main application logic. In this article, I will guide you through the process of hiding ignored files in Jest coverage reports, providing a detailed and multi-dimensional introduction.
Why Hide Ignored Files in Jest Coverage Reports?
Before diving into the technical aspects, let’s understand why you might want to hide ignored files in Jest coverage reports. Here are a few reasons:
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Focus on critical code: By hiding ignored files, you can concentrate on the code that is actually part of your application, making it easier to identify areas that require improvement.
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Enhanced readability: Coverage reports can become cluttered with ignored files, making it difficult to interpret the results. Hiding these files can improve the readability of the report.
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Customization: You might have specific requirements for your coverage report, and hiding ignored files allows you to tailor the report to your needs.
How to Hide Ignored Files in Jest Coverage Reports
Now that we understand the reasons for hiding ignored files, let’s explore the steps involved in achieving this:
1. Configure Jest to Ignore Files
First, you need to configure Jest to ignore the files you want to exclude from coverage reports. You can do this by adding a testMatch pattern in your Jest configuration file (usually jest.config.js):
module.exports = { testMatch: [ '/.js', '!/node_modules/', '!/test/', '!/dist/', ],};In the above example, the files in the node_modules, test, and dist directories are ignored.
2. Generate Coverage Report
After configuring Jest to ignore files, you can generate a coverage report using a tool like istanbul. To do this, run the following command in your project directory:
npm install --save-dev istanbulistanbul cover node_modules/jest-cli/bin/jest -- --coverageThis command will execute Jest with coverage enabled and generate a coverage report in the coverage directory.
3. Customize Coverage Report
Now that you have a coverage report, you can customize it to hide ignored files. One way to achieve this is by using a tool like istanbul-reports, which provides various report formats. To hide ignored files, you can use the text-summary format with the ignore option:
istanbul-reports text-summary --ignore node_modules/ test/ dist/ < coverage/coverage-final.jsonThis command will generate a text summary of the coverage report, excluding the ignored files.
Example: Customizing Coverage Report with Table
Let’s say you want to display the coverage report in a table format. You can use the text-table format provided by istanbul-reports with the ignore option:
istanbul-reports text-table --ignore node_modules/ test/ dist/ < coverage/coverage-final.jsonHere’s an example of the output:
| File | Statements | Branches | Functions | Lines |
|---|---|---|---|---|
| src/app.js | 100% | 100% | 100% | 100% |
| src/utils.js | 100% | 100% | 100% | 100% |
