diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8b912ba..06c449c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,7 +33,13 @@ jobs:
           php-version: ${{ matrix.php }}
           coverage: xdebug
       - run: composer install
-      - run: vendor/bin/phpunit --coverage-text ${{ matrix.php < 7.3 && '-c phpunit.xml.legacy' || '' }}
+      - run: vendor/bin/phpunit --coverage-text --coverage-clover clover.xml ${{ matrix.php < 7.3 && '-c phpunit.xml.legacy' || '' }}
+      - name: Check 100% code coverage
+        shell: php {0}
+        run: |
+          <?php
+          $metrics = simplexml_load_file('clover.xml')->project->metrics;
+          exit((int) $metrics['statements'] === (int) $metrics['coveredstatements'] ? 0 : 1);
 
   PHPUnit-hhvm:
     name: PHPUnit (HHVM)
diff --git a/README.md b/README.md
index 3a60ec3..d70c0f2 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,7 @@
 # clue/reactphp-csv
 
 [![CI status](https://github.com/clue/reactphp-csv/actions/workflows/ci.yml/badge.svg)](https://github.com/clue/reactphp-csv/actions)
+[![code coverage](https://img.shields.io/badge/code%20coverage-100%25-success)](#tests)
 [![installs on Packagist](https://img.shields.io/packagist/dt/clue/reactphp-csv?color=blue&label=installs%20on%20Packagist)](https://packagist.org/packages/clue/reactphp-csv)
 
 Streaming CSV (Comma-Separated Values or Character-Separated Values) parser and encoder for [ReactPHP](https://reactphp.org/).
@@ -411,6 +412,14 @@ To run the test suite, go to the project root and run:
 vendor/bin/phpunit
 ```
 
+The test suite is set up to always ensure 100% code coverage across all
+supported environments. If you have the Xdebug extension installed, you can also
+generate a code coverage report locally like this:
+
+```bash
+XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-text
+```
+
 ## License
 
 This project is released under the permissive [MIT license](LICENSE).
diff --git a/src/Encoder.php b/src/Encoder.php
index fe5d39f..4dc9d2d 100644
--- a/src/Encoder.php
+++ b/src/Encoder.php
@@ -82,7 +82,7 @@ public function write($data)
 
         // manually replace custom EOL on PHP < 8.1
         if (\PHP_VERSION_ID < 80100 && $this->eol !== "\n") {
-            $data = \substr($data, 0, -1) . $this->eol;
+            $data = \substr($data, 0, -1) . $this->eol; // @codeCoverageIgnore
         }
 
         return $this->output->write($data);