diff --git a/src/Data/ProcessedCodeCoverageDataMapper.php b/src/Data/ProcessedCodeCoverageDataMapper.php
new file mode 100644
index 000000000..24e927430
--- /dev/null
+++ b/src/Data/ProcessedCodeCoverageDataMapper.php
@@ -0,0 +1,49 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-code-coverage.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\CodeCoverage\Data;
+
+use function json_decode;
+use function json_encode;
+
+/**
+ * @internal This class is not covered by the backward compatibility promise for phpunit/php-code-coverage
+ *
+ * @psalm-import-type XdebugFunctionCoverageType from \SebastianBergmann\CodeCoverage\Driver\XdebugDriver
+ *
+ * @psalm-type TestIdType = string
+ */
+final class ProcessedCodeCoverageDataMapper
+{
+    public const KEY_LINE_COVERAGE     = 'lineCoverage';
+    public const KEY_FUNCTION_COVERAGE = 'functionCoverage';
+
+    public function toJson(ProcessedCodeCoverageData $processedCodeCoverageData): string
+    {
+        $arrayMapping = [
+            self::KEY_LINE_COVERAGE     => $processedCodeCoverageData->lineCoverage(),
+            self::KEY_FUNCTION_COVERAGE => $processedCodeCoverageData->functionCoverage(),
+        ];
+
+        return json_encode($arrayMapping);
+    }
+
+    public function fromJson(string $json): ProcessedCodeCoverageData
+    {
+        /** @var array<array-key, array<array-key, mixed>> */
+        $unserializedData = json_decode($json, true);
+
+        $processedCodeCoverageData = new ProcessedCodeCoverageData;
+
+        $processedCodeCoverageData->setLineCoverage($unserializedData[self::KEY_LINE_COVERAGE]);
+        $processedCodeCoverageData->setFunctionCoverage($unserializedData[self::KEY_FUNCTION_COVERAGE]);
+
+        return $processedCodeCoverageData;
+    }
+}
diff --git a/tests/tests/Data/ProcessedCodeCoverageDataMapperTest.php b/tests/tests/Data/ProcessedCodeCoverageDataMapperTest.php
new file mode 100644
index 000000000..281318702
--- /dev/null
+++ b/tests/tests/Data/ProcessedCodeCoverageDataMapperTest.php
@@ -0,0 +1,178 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-code-coverage.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\CodeCoverage\Data;
+
+use function file_get_contents;
+use function iterator_count;
+use function json_decode;
+use function unlink;
+use FilesystemIterator;
+use SebastianBergmann\CodeCoverage\Report\Xml\Facade;
+use SebastianBergmann\CodeCoverage\TestCase;
+
+final class ProcessedCodeCoverageDataMapperTest extends TestCase
+{
+    private static string $TEST_REPORT_PATH_SOURCE;
+
+    public static function setUpBeforeClass(): void
+    {
+        parent::setUpBeforeClass();
+
+        self::$TEST_REPORT_PATH_SOURCE = TEST_FILES_PATH . 'Report' . DIRECTORY_SEPARATOR . 'XML';
+    }
+
+    protected function tearDown(): void
+    {
+        parent::tearDown();
+
+        if (!file_exists(self::$TEST_TMP_PATH)) {
+            return;
+        }
+
+        foreach (new FilesystemIterator(self::$TEST_TMP_PATH) as $path => $fileInfo) {
+            /* @var \SplFileInfo $fileInfo */
+            unlink($fileInfo->getPathname());
+        }
+    }
+
+    public function testToJsonLineCoverageForBankAccount(): void
+    {
+        $coverage    = $this->getLineCoverageForBankAccount()->getData();
+        $decodedJson = $this->getDecodedJsonForProcessedCodeCoverage($coverage);
+
+        $this->assertEquals(
+            $coverage->lineCoverage(),
+            $decodedJson[ProcessedCodeCoverageDataMapper::KEY_LINE_COVERAGE],
+        );
+
+        $this->assertEquals(
+            $coverage->functionCoverage(),
+            $decodedJson[ProcessedCodeCoverageDataMapper::KEY_FUNCTION_COVERAGE],
+        );
+    }
+
+    public function testToJsonPathCoverageForBankAccount(): void
+    {
+        $coverage    = $this->getPathCoverageForBankAccount()->getData();
+        $decodedJson = $this->getDecodedJsonForProcessedCodeCoverage($coverage);
+
+        $this->assertEquals(
+            $coverage->lineCoverage(),
+            $decodedJson[ProcessedCodeCoverageDataMapper::KEY_LINE_COVERAGE],
+        );
+
+        $this->assertEquals(
+            $coverage->functionCoverage(),
+            $decodedJson[ProcessedCodeCoverageDataMapper::KEY_FUNCTION_COVERAGE],
+        );
+    }
+
+    public function testFromJsonCoverageForBankAccount(): void
+    {
+        $coverage             = $this->getPathCoverageForBankAccount()->getData();
+        $unserializedCoverage = $this->serializeAndUnserializeToJson($coverage);
+
+        $this->assertEquals(
+            $coverage->lineCoverage(),
+            $unserializedCoverage->lineCoverage(),
+        );
+
+        $this->assertEquals(
+            $coverage->functionCoverage(),
+            $unserializedCoverage->functionCoverage(),
+        );
+    }
+
+    public function testFromJsonPathCoverageForBankAccount(): void
+    {
+        $coverage             = $this->getPathCoverageForBankAccount()->getData();
+        $unserializedCoverage = $this->serializeAndUnserializeToJson($coverage);
+
+        $this->assertEquals(
+            $coverage->lineCoverage(),
+            $unserializedCoverage->lineCoverage(),
+        );
+
+        $this->assertEquals(
+            $coverage->functionCoverage(),
+            $unserializedCoverage->functionCoverage(),
+        );
+    }
+
+    /**
+     * I don't expect this test to survive in the PR, but I am trying to
+     * produce the final XML format via the JSON serialization to ensure
+     * that I have everything I need in the JSON format.
+     */
+    public function testFromJsonLineCoverageForBankAccountToXml(): void
+    {
+        $coverage             = $this->getLineCoverageForBankAccount();
+        $unserializedCoverage = $this->serializeAndUnserializeToJson($coverage->getData());
+        $coverage->setData($unserializedCoverage);
+
+        $expectedFilesPath = self::$TEST_REPORT_PATH_SOURCE . DIRECTORY_SEPARATOR . 'CoverageForBankAccount';
+
+        $xml = new Facade('1.0.0');
+        $xml->process($coverage, self::$TEST_TMP_PATH);
+
+        $this->assertFilesEquals($expectedFilesPath, self::$TEST_TMP_PATH);
+    }
+
+    private function getDecodedJsonForProcessedCodeCoverage(ProcessedCodeCoverageData $processedCodeCoverage): array
+    {
+        $dataMapper = new ProcessedCodeCoverageDataMapper;
+        $json       = $dataMapper->toJson($processedCodeCoverage);
+
+        return json_decode($json, true);
+    }
+
+    /**
+     * Doing it this way while the JSON format is being developed, though I expect we'd have a
+     * fixture file in the future.
+     */
+    private function serializeAndUnserializeToJson(ProcessedCodeCoverageData $processedCodeCoverage): ProcessedCodeCoverageData
+    {
+        $dataMapper = new ProcessedCodeCoverageDataMapper;
+        $json       = $dataMapper->toJson($processedCodeCoverage);
+
+        // Instantiate a new data mapper out of an abundance of caution to ensure we have no
+        // persisted state from the serializing instance.
+        $dataMapper = new ProcessedCodeCoverageDataMapper;
+
+        return $dataMapper->fromJson($json);
+    }
+
+    private function assertFilesEquals(string $expectedFilesPath, string $actualFilesPath): void
+    {
+        $expectedFilesIterator = new FilesystemIterator($expectedFilesPath);
+        $actualFilesIterator   = new FilesystemIterator($actualFilesPath);
+
+        $this->assertEquals(
+            iterator_count($expectedFilesIterator),
+            iterator_count($actualFilesIterator),
+            'Generated files and expected files not match',
+        );
+
+        foreach ($expectedFilesIterator as $fileInfo) {
+            /* @var \SplFileInfo $fileInfo */
+            $filename = $fileInfo->getFilename();
+
+            $actualFile = $actualFilesPath . DIRECTORY_SEPARATOR . $filename;
+
+            $this->assertFileExists($actualFile);
+
+            $this->assertStringMatchesFormatFile(
+                $fileInfo->getPathname(),
+                file_get_contents($actualFile),
+                "{$filename} not match",
+            );
+        }
+    }
+}