diff --git a/DEVELOP.rst b/DEVELOP.rst
index f577bf60..ca6c4a9a 100644
--- a/DEVELOP.rst
+++ b/DEVELOP.rst
@@ -81,15 +81,15 @@ Installation
 
 Install prerequisites::
 
-    # Install different PHP releases.
-    brew install php@7.3 php@7.4 php@8.0 composer
+    # Install different PHP releases and Composer.
+    brew install php@7.3 php@7.4 php@8.0 brew-php-switcher composer
 
     # Select PHP version.
     brew-php-switcher 7.3
     brew-php-switcher 7.4
     brew-php-switcher 8.0
 
-    # Install xdebug extension for tracking code coverage.
+    # Install `xdebug` extension into each environment for tracking code coverage.
     pecl install xdebug
 
 Get the sources::
@@ -113,9 +113,19 @@ Running the Tests
         --mount type=bind,source=$PWD/test/provisioning/truststore,target=/vagrant/test/provisioning/truststore \
         --publish 4200:4200 --publish 5432:5432 crate/crate:nightly
 
-    # Run test suite
+    # Run test suite on current/default version of PHP
     composer run test
 
+    # Run tests on both PHP7 and PHP8 to get the full picture of coverage
+    composer run multicover
+    open build/multicover/html/index.html
+
+
+Invoke code style checks
+========================
+
+::
+
     # Run code style checks
     composer run check-style
 
diff --git a/composer.json b/composer.json
index 702acf96..822c4497 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,8 @@
     "require-dev": {
         "phpunit/phpunit": "^9.5",
         "phpstan/phpstan": "^0.12",
-        "squizlabs/php_codesniffer": "^3.5"
+        "squizlabs/php_codesniffer": "^3.5",
+        "nimut/phpunit-merger": "^1.1"
     },
     "autoload-dev": {
         "psr-0": {
@@ -35,6 +36,8 @@
     },
     "scripts": {
         "test": "XDEBUG_MODE=coverage phpunit --coverage-clover build/logs/clover.xml",
+        "coverage-html": "XDEBUG_MODE=coverage phpunit --coverage-html build/logs/html",
+        "multicover": "./devtools/php-multicover.sh",
         "check-style": "phpcs",
         "fix-style": "phpcbf"
     }
diff --git a/composer.lock b/composer.lock
index 6a89f3e7..8717f23a 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "788e6343538a0ba45e412100c38fac81",
+    "content-hash": "ad611bed50a7bdc4729b138a4d42c526",
     "packages": [
         {
             "name": "guzzlehttp/guzzle",
@@ -572,6 +572,77 @@
             },
             "time": "2020-12-20T10:01:03+00:00"
         },
+        {
+            "name": "nimut/phpunit-merger",
+            "version": "1.1.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/Nimut/phpunit-merger.git",
+                "reference": "edec3fc30e005540fdec91bea9a33b0297c20742"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/Nimut/phpunit-merger/zipball/edec3fc30e005540fdec91bea9a33b0297c20742",
+                "reference": "edec3fc30e005540fdec91bea9a33b0297c20742",
+                "shasum": ""
+            },
+            "require": {
+                "ext-dom": "*",
+                "ext-json": "*",
+                "ext-simplexml": "*",
+                "php": ">=7.0.8 <7.5",
+                "phpunit/php-code-coverage": ">=5.0 <10.0",
+                "symfony/console": ">=2.7 <6.0",
+                "symfony/finder": ">=2.7 <6.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": ">=6.0 <10.0",
+                "symfony/filesystem": ">=2.7 <6.0"
+            },
+            "suggest": {
+                "friendsofphp/php-cs-fixer": "Tool to automatically fix PHP coding standards issues"
+            },
+            "bin": [
+                "bin/phpunit-merger"
+            ],
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Nimut\\PhpunitMerger\\": "src/PhpunitMerger/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "GPL-2.0+"
+            ],
+            "authors": [
+                {
+                    "name": "Nicole Cordes",
+                    "email": "typo3@cordes.co",
+                    "homepage": "https://www.biz-design.biz",
+                    "role": "Developer"
+                },
+                {
+                    "name": "Helmut Hummel",
+                    "email": "info@helhum.io",
+                    "homepage": "https://helhum.io",
+                    "role": "Developer"
+                }
+            ],
+            "description": "Merge multiple PHPUnit reports into one file",
+            "homepage": "https://github.com/Nimut/phpunit-merger",
+            "keywords": [
+                "TYPO3 CMS",
+                "coverage",
+                "phpunit",
+                "sonarqube"
+            ],
+            "support": {
+                "issues": "https://github.com/Nimut/phpunit-merger/issues",
+                "source": "https://github.com/Nimut/phpunit-merger/tree/1.1.0"
+            },
+            "time": "2020-10-06T12:13:54+00:00"
+        },
         {
             "name": "phar-io/manifest",
             "version": "2.0.1",
@@ -1389,6 +1460,59 @@
             ],
             "time": "2021-02-02T14:45:58+00:00"
         },
+        {
+            "name": "psr/container",
+            "version": "1.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/container.git",
+                "reference": "b7ce3b176482dbbc1245ebf52b181af44c2cf55f"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/container/zipball/b7ce3b176482dbbc1245ebf52b181af44c2cf55f",
+                "reference": "b7ce3b176482dbbc1245ebf52b181af44c2cf55f",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Container\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "http://www.php-fig.org/"
+                }
+            ],
+            "description": "Common Container Interface (PHP FIG PSR-11)",
+            "homepage": "https://github.com/php-fig/container",
+            "keywords": [
+                "PSR-11",
+                "container",
+                "container-interface",
+                "container-interop",
+                "psr"
+            ],
+            "support": {
+                "issues": "https://github.com/php-fig/container/issues",
+                "source": "https://github.com/php-fig/container/tree/master"
+            },
+            "time": "2017-02-14T16:28:37+00:00"
+        },
         {
             "name": "sebastian/cli-parser",
             "version": "1.0.1",
@@ -2409,6 +2533,164 @@
             },
             "time": "2020-10-23T02:01:07+00:00"
         },
+        {
+            "name": "symfony/console",
+            "version": "v5.2.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/console.git",
+                "reference": "89d4b176d12a2946a1ae4e34906a025b7b6b135a"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/console/zipball/89d4b176d12a2946a1ae4e34906a025b7b6b135a",
+                "reference": "89d4b176d12a2946a1ae4e34906a025b7b6b135a",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.5",
+                "symfony/polyfill-mbstring": "~1.0",
+                "symfony/polyfill-php73": "^1.8",
+                "symfony/polyfill-php80": "^1.15",
+                "symfony/service-contracts": "^1.1|^2",
+                "symfony/string": "^5.1"
+            },
+            "conflict": {
+                "symfony/dependency-injection": "<4.4",
+                "symfony/dotenv": "<5.1",
+                "symfony/event-dispatcher": "<4.4",
+                "symfony/lock": "<4.4",
+                "symfony/process": "<4.4"
+            },
+            "provide": {
+                "psr/log-implementation": "1.0"
+            },
+            "require-dev": {
+                "psr/log": "~1.0",
+                "symfony/config": "^4.4|^5.0",
+                "symfony/dependency-injection": "^4.4|^5.0",
+                "symfony/event-dispatcher": "^4.4|^5.0",
+                "symfony/lock": "^4.4|^5.0",
+                "symfony/process": "^4.4|^5.0",
+                "symfony/var-dumper": "^4.4|^5.0"
+            },
+            "suggest": {
+                "psr/log": "For using the console logger",
+                "symfony/event-dispatcher": "",
+                "symfony/lock": "",
+                "symfony/process": ""
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Console\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Eases the creation of beautiful and testable command line interfaces",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "cli",
+                "command line",
+                "console",
+                "terminal"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/console/tree/v5.2.3"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-28T22:06:19+00:00"
+        },
+        {
+            "name": "symfony/finder",
+            "version": "v5.2.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/finder.git",
+                "reference": "4adc8d172d602008c204c2e16956f99257248e03"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/finder/zipball/4adc8d172d602008c204c2e16956f99257248e03",
+                "reference": "4adc8d172d602008c204c2e16956f99257248e03",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.5"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\Finder\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Finds files and directories via an intuitive fluent interface",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/finder/tree/v5.2.3"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-28T22:06:19+00:00"
+        },
         {
             "name": "symfony/polyfill-ctype",
             "version": "v1.22.1",
@@ -2488,6 +2770,575 @@
             ],
             "time": "2021-01-07T16:49:33+00:00"
         },
+        {
+            "name": "symfony/polyfill-intl-grapheme",
+            "version": "v1.22.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-intl-grapheme.git",
+                "reference": "5601e09b69f26c1828b13b6bb87cb07cddba3170"
+            },
+            "dist": {
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+                "url": "https://api.github.com/repos/symfony/polyfill-intl-grapheme/zipball/5601e09b69f26c1828b13b6bb87cb07cddba3170",
+                "reference": "5601e09b69f26c1828b13b6bb87cb07cddba3170",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "suggest": {
+                "ext-intl": "For best performance"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "1.22-dev"
+                },
+                "thanks": {
+                    "name": "symfony/polyfill",
+                    "url": "https://github.com/symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Polyfill\\Intl\\Grapheme\\": ""
+                },
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill for intl's grapheme_* functions",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
+                "grapheme",
+                "intl",
+                "polyfill",
+                "portable",
+                "shim"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/polyfill-intl-grapheme/tree/v1.22.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-22T09:19:47+00:00"
+        },
+        {
+            "name": "symfony/polyfill-intl-normalizer",
+            "version": "v1.22.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-intl-normalizer.git",
+                "reference": "43a0283138253ed1d48d352ab6d0bdb3f809f248"
+            },
+            "dist": {
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+                "url": "https://api.github.com/repos/symfony/polyfill-intl-normalizer/zipball/43a0283138253ed1d48d352ab6d0bdb3f809f248",
+                "reference": "43a0283138253ed1d48d352ab6d0bdb3f809f248",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "suggest": {
+                "ext-intl": "For best performance"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "1.22-dev"
+                },
+                "thanks": {
+                    "name": "symfony/polyfill",
+                    "url": "https://github.com/symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Polyfill\\Intl\\Normalizer\\": ""
+                },
+                "files": [
+                    "bootstrap.php"
+                ],
+                "classmap": [
+                    "Resources/stubs"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill for intl's Normalizer class and related functions",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
+                "intl",
+                "normalizer",
+                "polyfill",
+                "portable",
+                "shim"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/polyfill-intl-normalizer/tree/v1.22.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-22T09:19:47+00:00"
+        },
+        {
+            "name": "symfony/polyfill-mbstring",
+            "version": "v1.22.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-mbstring.git",
+                "reference": "5232de97ee3b75b0360528dae24e73db49566ab1"
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+                "reference": "5232de97ee3b75b0360528dae24e73db49566ab1",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "suggest": {
+                "ext-mbstring": "For best performance"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "1.22-dev"
+                },
+                "thanks": {
+                    "name": "symfony/polyfill",
+                    "url": "https://github.com/symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Polyfill\\Mbstring\\": ""
+                },
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill for the Mbstring extension",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
+                "mbstring",
+                "polyfill",
+                "portable",
+                "shim"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/polyfill-mbstring/tree/v1.22.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-22T09:19:47+00:00"
+        },
+        {
+            "name": "symfony/polyfill-php73",
+            "version": "v1.22.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-php73.git",
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+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "1.22-dev"
+                },
+                "thanks": {
+                    "name": "symfony/polyfill",
+                    "url": "https://github.com/symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Polyfill\\Php73\\": ""
+                },
+                "files": [
+                    "bootstrap.php"
+                ],
+                "classmap": [
+                    "Resources/stubs"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill backporting some PHP 7.3+ features to lower PHP versions",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
+                "polyfill",
+                "portable",
+                "shim"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/polyfill-php73/tree/v1.22.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-07T16:49:33+00:00"
+        },
+        {
+            "name": "symfony/polyfill-php80",
+            "version": "v1.22.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/polyfill-php80.git",
+                "reference": "dc3063ba22c2a1fd2f45ed856374d79114998f91"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/polyfill-php80/zipball/dc3063ba22c2a1fd2f45ed856374d79114998f91",
+                "reference": "dc3063ba22c2a1fd2f45ed856374d79114998f91",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-main": "1.22-dev"
+                },
+                "thanks": {
+                    "name": "symfony/polyfill",
+                    "url": "https://github.com/symfony/polyfill"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Polyfill\\Php80\\": ""
+                },
+                "files": [
+                    "bootstrap.php"
+                ],
+                "classmap": [
+                    "Resources/stubs"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Ion Bazan",
+                    "email": "ion.bazan@gmail.com"
+                },
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Symfony polyfill backporting some PHP 8.0+ features to lower PHP versions",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "compatibility",
+                "polyfill",
+                "portable",
+                "shim"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/polyfill-php80/tree/v1.22.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-07T16:49:33+00:00"
+        },
+        {
+            "name": "symfony/service-contracts",
+            "version": "v2.2.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/service-contracts.git",
+                "reference": "d15da7ba4957ffb8f1747218be9e1a121fd298a1"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/service-contracts/zipball/d15da7ba4957ffb8f1747218be9e1a121fd298a1",
+                "reference": "d15da7ba4957ffb8f1747218be9e1a121fd298a1",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.5",
+                "psr/container": "^1.0"
+            },
+            "suggest": {
+                "symfony/service-implementation": ""
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.2-dev"
+                },
+                "thanks": {
+                    "name": "symfony/contracts",
+                    "url": "https://github.com/symfony/contracts"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Contracts\\Service\\": ""
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Generic abstractions related to writing services",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "abstractions",
+                "contracts",
+                "decoupling",
+                "interfaces",
+                "interoperability",
+                "standards"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/service-contracts/tree/master"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2020-09-07T11:33:47+00:00"
+        },
+        {
+            "name": "symfony/string",
+            "version": "v5.2.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/string.git",
+                "reference": "c95468897f408dd0aca2ff582074423dd0455122"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/string/zipball/c95468897f408dd0aca2ff582074423dd0455122",
+                "reference": "c95468897f408dd0aca2ff582074423dd0455122",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.5",
+                "symfony/polyfill-ctype": "~1.8",
+                "symfony/polyfill-intl-grapheme": "~1.0",
+                "symfony/polyfill-intl-normalizer": "~1.0",
+                "symfony/polyfill-mbstring": "~1.0",
+                "symfony/polyfill-php80": "~1.15"
+            },
+            "require-dev": {
+                "symfony/error-handler": "^4.4|^5.0",
+                "symfony/http-client": "^4.4|^5.0",
+                "symfony/translation-contracts": "^1.1|^2",
+                "symfony/var-exporter": "^4.4|^5.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Symfony\\Component\\String\\": ""
+                },
+                "files": [
+                    "Resources/functions.php"
+                ],
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Nicolas Grekas",
+                    "email": "p@tchwork.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Provides an object-oriented API to strings and deals with bytes, UTF-8 code points and grapheme clusters in a unified way",
+            "homepage": "https://symfony.com",
+            "keywords": [
+                "grapheme",
+                "i18n",
+                "string",
+                "unicode",
+                "utf-8",
+                "utf8"
+            ],
+            "support": {
+                "source": "https://github.com/symfony/string/tree/v5.2.3"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2021-01-25T15:14:59+00:00"
+        },
         {
             "name": "theseer/tokenizer",
             "version": "1.2.0",
diff --git a/devtools/php-multicover.sh b/devtools/php-multicover.sh
new file mode 100755
index 00000000..acf796ad
--- /dev/null
+++ b/devtools/php-multicover.sh
@@ -0,0 +1,55 @@
+#!/bin/sh
+#
+# About
+# =====
+#
+# Run tests with coverage on both PHP7 and PHP8,
+# merge coverage reports and render them as HTML.
+#
+# Please adjust the paths to the PHP interpreters
+# to fit your needs. Make sure to `pecl install xdebug`
+# in both PHP7 and PHP8 environments beforehand.
+#
+# Setup
+# =====
+#
+# Install different PHP releases and Composer::
+#
+#   brew install php@7.3 php@7.4 php@8.0 brew-php-switcher composer
+#
+# Select PHP version::
+#
+#   brew-php-switcher 7.3
+#   brew-php-switcher 7.4
+#   brew-php-switcher 8.0
+#
+# Install `xdebug` extension into each environment for tracking code coverage::
+#
+#   pecl install xdebug
+#
+
+# Define shortcuts to executables.
+php7=/usr/local/Cellar/php@7.4/7.4.15/bin/php
+php8=/usr/local/Cellar/php/8.0.2/bin/php
+phpunit="$(pwd)/vendor/bin/phpunit"
+phpunit_merger="$(pwd)/vendor/bin/phpunit-merger"
+
+# Prepare output directories.
+mkdir -p build/multicover/reports build/multicover/html
+rm -rf build/multicover/reports/* build/multicover/html/*
+
+# Enable coverage tracing.
+export XDEBUG_MODE=coverage
+
+# Run tests with PHP coverage output on both PHP7 and PHP8.
+echo Running tests with coverage on PHP7
+$php7 $phpunit --coverage-php build/multicover/reports/clover-php7.php
+echo; echo
+
+echo Running tests with coverage on PHP8
+$php8 $phpunit --coverage-php build/multicover/reports/clover-php8.php
+echo; echo
+
+# Merge coverage reports and generate HTML output.
+echo Merging test reports
+$php8 $phpunit_merger coverage build/multicover/reports --html=build/multicover/html /dev/null