diff --git a/.gitattributes b/.gitattributes
index 085a2fb..2108458 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,5 +1,6 @@
 /.github/                       export-ignore
 /.phive/                        export-ignore
+/src/Test/                      export-ignore
 /.editorconfig                  export-ignore
 /.gitattributes                 export-ignore
 /.gitignore                     export-ignore
@@ -9,6 +10,8 @@
 /composer-require-checker.json  export-ignore
 /composer.lock                  export-ignore
 /Makefile                       export-ignore
+/phpbench.json                  export-ignore
+/phpunit.xml                    export-ignore
 /psalm-baseline.xml             export-ignore
 /psalm.xml                      export-ignore
 /rector.php                     export-ignore
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 7ca8b1a..06eb960 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -46,6 +46,28 @@ make dependency-analysis
 
 to run a dependency analysis.
 
+## Mutation Tests
+
+We are using [`infection/infection`](https://github.com/infection/infection) to ensure a minimum quality of the tests.
+
+Enable `Xdebug` and run
+
+```sh
+make mutation-tests
+```
+
+to run mutation tests.
+
+## Performance Tests
+
+We are using [`phpbench/phpbench`](https://github.com/phpbench/phpbench) to control the performance of our production code.
+
+```sh
+make performance-tests
+```
+
+to run performance tests.
+
 ## Refactoring
 
 We are using [`rector/rector`](https://github.com/rectorphp/rector) to automatically refactor code.
@@ -94,6 +116,17 @@ to regenerate the baseline in [`../psalm-baseline.xml`](../psalm-baseline.xml).
 
 :exclamation: Ideally, the baseline should shrink over time.
 
+## Tests
+
+We are using [`phpunit/phpunit`](https://github.com/sebastianbergmann/phpunit) to drive the development.
+
+Run
+
+```sh
+make tests
+```
+
+to run all the tests.
 
 ## Extra lazy?
 
@@ -103,7 +136,7 @@ Run
 make
 ```
 
-to automatically refactor code, enforce coding standards, and run a static code analysis!
+to automatically refactor code, enforce coding standards, run a static code analysis, run tests, run performance tests, and run mutation tests!
 
 ## Help
 
diff --git a/.github/settings.yml b/.github/settings.yml
index 57ebbf4..8946ccf 100644
--- a/.github/settings.yml
+++ b/.github/settings.yml
@@ -15,11 +15,15 @@ branches:
       required_status_checks:
         checks:
           - context: "Autoloader (8.2, locked)"
+          - context: "Code Coverage (8.2, locked)"
           - context: "Coding Standards (8.2, locked)"
           - context: "Dependency Analysis (8.2, locked)"
+          - context: "Mutation Tests (8.2, locked)"
+          - context: "Performance Tests (8.2, locked)"
           - context: "Refactoring (8.2, locked)"
           - context: "Security Analysis (8.2, locked)"
           - context: "Static Code Analysis (8.2, locked)"
+          - context: "Tests (8.2, locked)"
         strict: false
       restrictions: null
 
diff --git a/.github/workflows/integrate.yaml b/.github/workflows/integrate.yaml
index d557ea6..0de4537 100644
--- a/.github/workflows/integrate.yaml
+++ b/.github/workflows/integrate.yaml
@@ -62,6 +62,62 @@ jobs:
       - name: "Test autoloader for production"
         run: "php autoloader.php"
 
+  code-coverage:
+    name: "Code Coverage"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "8.2"
+
+        dependencies:
+          - "locked"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3.3.0"
+
+      - name: "Set up PHP"
+        uses: "shivammathur/setup-php@2.24.0"
+        with:
+          coverage: "xdebug"
+          extensions: "none, ctype, dom, json, mbstring, phar, simplexml, tokenizer, xml, xmlwriter"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Set up problem matchers for PHP"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/php.json\""
+
+      - name: "Set up problem matchers for phpunit/phpunit"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/phpunit.json\""
+
+      - name: "Determine composer cache directory"
+        uses: "ergebnis/.github/actions/composer/determine-cache-directory@1.8.0"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v3.2.6"
+        with:
+          path: "${{ env.COMPOSER_CACHE_DIR }}"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install ${{ matrix.dependencies }} dependencies with composer"
+        uses: "ergebnis/.github/actions/composer/install@1.8.0"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Collect code coverage with Xdebug and phpunit/phpunit"
+        env:
+          XDEBUG_MODE: "coverage"
+        run: "vendor/bin/phpunit --colors=always --configuration=phpunit.xml --coverage-clover=.build/phpunit/logs/clover.xml"
+
+      - name: "Send code coverage report to codecov.io"
+        uses: "codecov/codecov-action@v3.1.1"
+        with:
+          files: ".build/phpunit/logs/clover.xml"
+          token: "${{ secrets.CODECOV_TOKEN }}"
+
   coding-standards:
     name: "Coding Standards"
 
@@ -190,6 +246,98 @@ jobs:
       - name: "Run maglnet/composer-require-checker"
         run: ".phive/composer-require-checker check --ansi --config-file=$(pwd)/composer-require-checker.json"
 
+  mutation-tests:
+    name: "Mutation Tests"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "8.2"
+
+        dependencies:
+          - "locked"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3.3.0"
+
+      - name: "Set up PHP"
+        uses: "shivammathur/setup-php@2.24.0"
+        with:
+          coverage: "xdebug"
+          extensions: "none, ctype, dom, json, mbstring, phar, simplexml, tokenizer, xml, xmlwriter"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Set up problem matchers for PHP"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/php.json\""
+
+      - name: "Determine composer cache directory"
+        uses: "ergebnis/.github/actions/composer/determine-cache-directory@1.8.0"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v3.2.6"
+        with:
+          path: "${{ env.COMPOSER_CACHE_DIR }}"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install ${{ matrix.dependencies }} dependencies with composer"
+        uses: "ergebnis/.github/actions/composer/install@1.8.0"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Run mutation tests with Xdebug and infection/infection"
+        env:
+          XDEBUG_MODE: "coverage"
+        run: "vendor/bin/infection --ansi --configuration=infection.json --logger-github"
+
+  performance-tests:
+    name: "Performance Tests"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "8.2"
+
+        dependencies:
+          - "locked"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3.3.0"
+
+      - name: "Set up PHP"
+        uses: "shivammathur/setup-php@2.24.0"
+        with:
+          coverage: "none"
+          extensions: "none, ctype, dom, json, mbstring, phar, simplexml, tokenizer, xml, xmlwriter"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Set up problem matchers for PHP"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/php.json\""
+
+      - name: "Determine composer cache directory"
+        uses: "ergebnis/.github/actions/composer/determine-cache-directory@1.8.0"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v3.2.6"
+        with:
+          path: "${{ env.COMPOSER_CACHE_DIR }}"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install ${{ matrix.dependencies }} dependencies with composer"
+        uses: "ergebnis/.github/actions/composer/install@1.8.0"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Run performance tests with phpbench/phpbench"
+        run: "vendor/bin/phpbench run --config=phpbench.json src/Test/"
+
   refactoring:
     name: "Refactoring"
 
@@ -354,3 +502,53 @@ jobs:
 
       - name: "Run vimeo/psalm"
         run: "vendor/bin/psalm --config=psalm.xml --output-format=github --shepherd --show-info=false --stats --threads=4"
+
+  tests:
+    name: "Tests"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "8.2"
+
+        dependencies:
+          - "lowest"
+          - "locked"
+          - "highest"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3.3.0"
+
+      - name: "Set up PHP"
+        uses: "shivammathur/setup-php@2.24.0"
+        with:
+          coverage: "none"
+          extensions: "none, ctype, dom, json, mbstring, phar, simplexml, tokenizer, xml, xmlwriter"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Set up problem matchers for PHP"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/php.json\""
+
+      - name: "Set up problem matchers for phpunit/phpunit"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/phpunit.json\""
+
+      - name: "Determine composer cache directory"
+        uses: "ergebnis/.github/actions/composer/determine-cache-directory@1.8.0"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v3.2.6"
+        with:
+          path: "${{ env.COMPOSER_CACHE_DIR }}"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install ${{ matrix.dependencies }} dependencies with composer"
+        uses: "ergebnis/.github/actions/composer/install@1.8.0"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Run tests with phpunit/phpunit"
+        run: "vendor/bin/phpunit --colors=always --configuration=phpunit.xml"
diff --git a/Makefile b/Makefile
index 49c82f8..9266095 100644
--- a/Makefile
+++ b/Makefile
@@ -1,11 +1,16 @@
 .PHONY: it
-it: refactoring coding-standards security-analysis static-code-analysis autoloader ## Runs the refactoring, coding-standards, security-analysis, static-code-analysis, and autoloader targets
+it: refactoring coding-standards security-analysis static-code-analysis tests performance-tests mutation-tests autoloader ## Runs the refactoring, coding-standards, security-analysis, static-code-analysis, tests, performance-tests, mutation-tests, and autoloader targets
 
 .PHONY: autoloader
 autoloader: ## Dumps the autoloader for production and verifies that it does not include classes not intended for production
 	composer dump-autoload --no-dev --optimize
 	php autoloader.php
 
+.PHONY: code-coverage
+code-coverage: vendor ## Collects coverage from running unit tests with phpunit/phpunit
+	mkdir -p .build/phpunit
+	vendor/bin/phpunit --configuration=phpunit.xml --coverage-text
+
 .PHONY: coding-standards
 coding-standards: vendor ## Lints YAML files with yamllint, normalizes composer.json with ergebnis/composer-normalize, and fixes code style issues with friendsofphp/php-cs-fixer
 	yamllint -c .yamllint.yaml --strict .
@@ -21,6 +26,15 @@ dependency-analysis: phive vendor ## Runs a dependency analysis with maglnet/com
 help: ## Displays this list of targets with descriptions
 	@grep -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[32m%-30s\033[0m %s\n", $$1, $$2}'
 
+.PHONY: performance-tests
+performance-tests: vendor ## Runs performance tests with phpbench/phpbench
+	vendor/bin/phpbench run --config=phpbench.json src/Test/
+
+.PHONY: mutation-tests
+mutation-tests: vendor ## Runs mutation tests with infection/infection
+	mkdir -p .build/infection
+	vendor/bin/infection --configuration=infection.json
+
 .PHONY: phive
 phive: .phive ## Installs dependencies with phive
 	mkdir -p .build/phive/
@@ -47,6 +61,11 @@ static-code-analysis-baseline: vendor ## Generates a baseline for static code an
 	vendor/bin/psalm --config=psalm.xml --clear-cache
 	vendor/bin/psalm --config=psalm.xml --set-baseline=psalm-baseline.xml
 
+.PHONY: tests
+tests: vendor ## Runs tests with phpunit/phpunit
+	mkdir -p .build/phpunit
+	vendor/bin/phpunit --configuration=phpunit.xml
+
 vendor: composer.json composer.lock
 	composer validate --strict
 	composer install --no-interaction --no-progress
diff --git a/composer.json b/composer.json
index 5ac1537..87c8d69 100644
--- a/composer.json
+++ b/composer.json
@@ -34,7 +34,10 @@
   "autoload": {
     "psr-4": {
       "Localheinz\\OrganizingTestCodeInPhp\\": "src/"
-    }
+    },
+    "exclude-from-classmap": [
+      "/src/Test/"
+    ]
   },
   "config": {
     "allow-plugins": {
diff --git a/infection.json b/infection.json
new file mode 100644
index 0000000..e237036
--- /dev/null
+++ b/infection.json
@@ -0,0 +1,20 @@
+{
+  "ignoreMsiWithNoMutations": true,
+  "logs": {
+    "text": ".build/infection/infection-log.txt"
+  },
+  "minCoveredMsi": 100,
+  "minMsi": 100,
+  "phpUnit": {
+    "configDir": "."
+  },
+  "source": {
+    "directories": [
+      "src"
+    ],
+    "excludes": [
+      "Test/"
+    ]
+  },
+  "timeout": 10
+}
diff --git a/phpbench.json b/phpbench.json
new file mode 100644
index 0000000..4d5bd3e
--- /dev/null
+++ b/phpbench.json
@@ -0,0 +1,5 @@
+{
+  "$schema":"vendor/phpbench/phpbench/phpbench.schema.json",
+  "runner.bootstrap": "vendor/autoload.php",
+  "runner.file_pattern": "*.php"
+}
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..da3edd6
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,44 @@
+<?xml version="1.0"?>
+<phpunit
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+    beStrictAboutChangesToGlobalState="true"
+    beStrictAboutCoverageMetadata="true"
+    beStrictAboutOutputDuringTests="true"
+    beStrictAboutTestsThatDoNotTestAnything="true"
+    bootstrap="vendor/autoload.php"
+    cacheDirectory=".build/phpunit/unit/"
+    cacheResult="true"
+    colors="true"
+    columns="max"
+    displayDetailsOnIncompleteTests="true"
+    displayDetailsOnSkippedTests="true"
+    displayDetailsOnTestsThatTriggerDeprecations="true"
+    displayDetailsOnTestsThatTriggerErrors="true"
+    displayDetailsOnTestsThatTriggerNotices="true"
+    displayDetailsOnTestsThatTriggerWarnings="true"
+    executionOrder="random"
+    requireCoverageMetadata="true"
+    stopOnError="false"
+    stopOnFailure="false"
+    stopOnIncomplete="false"
+    stopOnSkipped="false"
+>
+    <coverage includeUncoveredFiles="true"/>
+    <extensions>
+        <bootstrap class="Ergebnis\PHPUnit\SlowTestDetector\Extension"/>
+    </extensions>
+    <source>
+        <include>
+            <directory suffix=".php">src/</directory>
+        </include>
+        <exclude>
+            <directory>src/Test/</directory>
+        </exclude>
+    </source>
+    <testsuites>
+        <testsuite name="Tests">
+            <directory>src/Test/</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index 10b8be1..9527e5f 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -1,10 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <files psalm-version="5.15.0@5c774aca4746caf3d239d9c8cadb9f882ca29352">
-  <file src="src/Example.php">
-    <PossiblyUnusedMethod>
-      <code>equals</code>
-      <code>fromString</code>
-      <code>toString</code>
-    </PossiblyUnusedMethod>
+  <file src="src/Test/ExampleBench.php">
+    <UnusedClass>
+      <code>ExampleBench</code>
+    </UnusedClass>
   </file>
 </files>
diff --git a/src/Test/ExampleBench.php b/src/Test/ExampleBench.php
new file mode 100644
index 0000000..65f3c26
--- /dev/null
+++ b/src/Test/ExampleBench.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2023 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/organizing-test-code-in-php
+ */
+
+namespace Localheinz\OrganizingTestCodeInPhp\Test;
+
+use Localheinz\OrganizingTestCodeInPhp\Example;
+
+final class ExampleBench
+{
+    /**
+     * @Revs(1000)
+     *
+     * @Iterations(5)
+     */
+    public function benchFromStringReturnsExample(): void
+    {
+        Example::fromString('foo');
+    }
+}
diff --git a/src/Test/ExampleTest.php b/src/Test/ExampleTest.php
new file mode 100644
index 0000000..97b7698
--- /dev/null
+++ b/src/Test/ExampleTest.php
@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2023 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/organizing-test-code-in-php
+ */
+
+namespace Localheinz\OrganizingTestCodeInPhp\Test;
+
+use Localheinz\OrganizingTestCodeInPhp\Example;
+use Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeBlank;
+use Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeEmpty;
+use PHPUnit\Framework;
+
+/**
+ * @internal
+ *
+ * @covers \Localheinz\OrganizingTestCodeInPhp\Example
+ *
+ * @uses \Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeBlank
+ * @uses \Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeEmpty
+ */
+final class ExampleTest extends Framework\TestCase
+{
+    use Helper;
+
+    /**
+     * @dataProvider \Ergebnis\DataProvider\StringProvider::empty
+     */
+    public function testFromStringRejectsEmptyValue(string $value): void
+    {
+        $this->expectException(ValueCanNotBeEmpty::class);
+
+        Example::fromString($value);
+    }
+
+    /**
+     * @dataProvider \Ergebnis\DataProvider\StringProvider::blank
+     */
+    public function testFromStringRejectsBlankValue(string $value): void
+    {
+        $this->expectException(ValueCanNotBeBlank::class);
+
+        Example::fromString($value);
+    }
+
+    public function testFromStringReturnsExample(): void
+    {
+        $value = self::faker()->word();
+
+        $example = Example::fromString($value);
+
+        self::assertSame($value, $example->toString());
+    }
+
+    public function testEqualsReturnsFalseWhenValueIsDifferent(): void
+    {
+        $faker = self::faker()->unique();
+
+        $one = Example::fromString($faker->word());
+        $two = Example::fromString($faker->word());
+
+        self::assertFalse($one->equals($two));
+    }
+
+    public function testEqualsReturnsTrueWhenValueIsSame(): void
+    {
+        $value = self::faker()->word();
+
+        $one = Example::fromString($value);
+        $two = Example::fromString($value);
+
+        self::assertTrue($one->equals($two));
+    }
+}
diff --git a/src/Test/Helper.php b/src/Test/Helper.php
new file mode 100644
index 0000000..9373b72
--- /dev/null
+++ b/src/Test/Helper.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2023 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/organizing-test-code-in-php
+ */
+
+namespace Localheinz\OrganizingTestCodeInPhp\Test;
+
+use Faker\Factory;
+use Faker\Generator;
+
+/**
+ * @internal
+ */
+trait Helper
+{
+    private static function faker(string $locale = 'en_US'): Generator
+    {
+        /**
+         * @var array<string, Generator>
+         */
+        static $fakers = [];
+
+        if (!\array_key_exists($locale, $fakers)) {
+            $faker = Factory::create($locale);
+
+            $faker->seed(9001);
+
+            $fakers[$locale] = $faker;
+        }
+
+        return $fakers[$locale];
+    }
+}
diff --git a/src/Test/ValueCanNotBeBlankTest.php b/src/Test/ValueCanNotBeBlankTest.php
new file mode 100644
index 0000000..dee83a4
--- /dev/null
+++ b/src/Test/ValueCanNotBeBlankTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2023 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/organizing-test-code-in-php
+ */
+
+namespace Localheinz\OrganizingTestCodeInPhp\Test;
+
+use Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeBlank;
+use PHPUnit\Framework;
+
+/**
+ * @internal
+ *
+ * @covers \Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeBlank
+ */
+final class ValueCanNotBeBlankTest extends Framework\TestCase
+{
+    public function testCreateReturnsException(): void
+    {
+        $exception = ValueCanNotBeBlank::create();
+
+        self::assertSame('Value can not be blank.', $exception->getMessage());
+    }
+}
diff --git a/src/Test/ValueCanNotBeEmptyTest.php b/src/Test/ValueCanNotBeEmptyTest.php
new file mode 100644
index 0000000..824e62a
--- /dev/null
+++ b/src/Test/ValueCanNotBeEmptyTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2023 Andreas Möller
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE.md file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/organizing-test-code-in-php
+ */
+
+namespace Localheinz\OrganizingTestCodeInPhp\Test;
+
+use Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeEmpty;
+use PHPUnit\Framework;
+
+/**
+ * @internal
+ *
+ * @covers \Localheinz\OrganizingTestCodeInPhp\ValueCanNotBeEmpty
+ */
+final class ValueCanNotBeEmptyTest extends Framework\TestCase
+{
+    public function testCreateReturnsException(): void
+    {
+        $exception = ValueCanNotBeEmpty::create();
+
+        self::assertSame('Value can not be empty.', $exception->getMessage());
+    }
+}