diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index a5b6b66..7caf4df 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -25,16 +25,18 @@ jobs:
           fetch-depth: 0
 
       - name: Lint Code Base
-        uses: github/super-linter/slim@v5
+        uses: github/super-linter/slim@v6
         env:
           # To report GitHub Actions status checks
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           LINTER_RULES_PATH: 'tools/linters'
+          LOG_LEVEL: NOTICE
           VALIDATE_ALL_CODEBASE: true
+          VALIDATE_CSS: true
+          VALIDATE_JAVASCRIPT_ES: true
           VALIDATE_JSON: true
           VALIDATE_PHP_BUILTIN: true
           VALIDATE_YAML: true
-          VALIDATE_XML: true
           VALIDATE_GITHUB_ACTIONS: true
 
   quality:
@@ -74,13 +76,14 @@ jobs:
       - name: Install Composer dependencies
         run: composer install --no-progress --prefer-dist --optimize-autoloader
 
-      #- name: Check code for hard dependencies missing in composer.json
-      #  run: composer-require-checker check composer.json
+      - name: Check code for hard dependencies missing in composer.json
+        run: composer-require-checker check --config-file tools/composer-require-checker.json composer.json
 
       - name: Check code for unused dependencies in composer.json
         run: |
           composer-unused \
-          --excludePackage=slevomat/coding-standard
+          --excludePackage=slevomat/coding-standard \
+          --excludePackage=symfony/phpunit-bridge
 
       - name: PHP Code Sniffer
         run: phpcs
@@ -140,3 +143,150 @@ jobs:
 
       - name: Security check for updated dependencies
         run: composer audit
+
+  unit-tests-linux:
+    name: "Unit tests, PHP ${{ matrix.php-versions }}, ${{ matrix.operating-system }}"
+    runs-on: ${{ matrix.operating-system }}
+    needs: [linter, quality, security]
+    strategy:
+      fail-fast: false
+      matrix:
+        operating-system: [ubuntu-latest]
+        php-versions: ['8.1', '8.2', '8.3']
+
+    steps:
+      - name: Setup PHP, with composer and extensions
+        # https://github.com/shivammathur/setup-php
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          extensions: ctype, date, dom, fileinfo, filter, hash, json, mbstring, mysql, openssl, pcre,\
+            pdo, pdo_sqlite, posix, soap, spl, xdebug, xml
+          tools: composer
+          ini-values: error_reporting=E_ALL, pcov.directory=.
+          coverage: pcov
+
+      - name: Setup problem matchers for PHP
+        run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+
+      - name: Setup problem matchers for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Set git to use LF
+        run: |
+          git config --global core.autocrlf false
+          git config --global core.eol lf
+
+      - uses: actions/checkout@v4
+
+      - name: Get composer cache directory
+        run: echo COMPOSER_CACHE="$(composer config cache-files-dir)" >> "$GITHUB_ENV"
+
+      - name: Cache composer dependencies
+        uses: actions/cache@v4
+        with:
+          path: $COMPOSER_CACHE
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install Composer dependencies
+        run: composer install --no-progress --prefer-dist --optimize-autoloader
+
+      - name: Run unit tests with coverage
+        if: ${{ matrix.php-versions == '8.3' }}
+        run: vendor/bin/phpunit
+
+      - name: Run unit tests (no coverage)
+        if: ${{ matrix.php-versions != '8.3' }}
+        run: vendor/bin/phpunit --no-coverage
+
+      - name: Save coverage data
+        if: ${{ matrix.php-versions == '8.3' }}
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-data
+          path: ${{ github.workspace }}/build
+
+  unit-tests-windows:
+    name: "Unit tests, PHP ${{ matrix.php-versions }}, ${{ matrix.operating-system }}"
+    runs-on: ${{ matrix.operating-system }}
+    needs: [linter, quality, security]
+    strategy:
+      fail-fast: true
+      matrix:
+        operating-system: [windows-latest]
+        php-versions: ['8.1', '8.2', '8.3']
+
+    steps:
+      - name: Setup PHP, with composer and extensions
+        # https://github.com/shivammathur/setup-php
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          extensions: ctype, dom, date, fileinfo, filter, hash, json, mbstring, mysql, openssl, pcre, \
+            pdo, pdo_sqlite, posix, soap, spl, xdebug, xml
+          tools: composer
+          ini-values: error_reporting=E_ALL
+          coverage: none
+
+      - name: Setup problem matchers for PHP
+        run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+
+      - name: Setup problem matchers for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Set git to use LF
+        run: |
+          git config --global core.autocrlf false
+          git config --global core.eol lf
+
+      - uses: actions/checkout@v4
+
+      - name: Get composer cache directory
+        run: echo COMPOSER_CACHE="$(composer config cache-files-dir)" >> "$env:GITHUB_ENV"
+
+      - name: Cache composer dependencies
+        uses: actions/cache@v4
+        with:
+          path: $COMPOSER_CACHE
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install Composer dependencies
+        run: composer install --no-progress --prefer-dist --optimize-autoloader --ignore-platform-req=ext-posix
+
+      - name: Run unit tests
+        run: vendor/bin/phpunit --no-coverage
+
+  coverage:
+    name: Code coverage
+    runs-on: [ubuntu-latest]
+    needs: [unit-tests-linux]
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/download-artifact@v4
+        with:
+          name: coverage-data
+          path: ${{ github.workspace }}/build
+
+      - name: Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: true
+          verbose: true
+
+  cleanup:
+    name: Cleanup artifacts
+    needs: [unit-tests-linux, coverage]
+    runs-on: [ubuntu-latest]
+    if: |
+      always() &&
+      needs.coverage.result == 'success' ||
+      (needs.unit-tests-linux == 'success' && needs.coverage == 'skipped')
+
+    steps:
+      - uses: geekyeggo/delete-artifact@v5
+        with:
+          name: coverage-data
diff --git a/composer.json b/composer.json
index d4231c4..0c0a296 100644
--- a/composer.json
+++ b/composer.json
@@ -15,15 +15,21 @@
             "SimpleSAML\\TestUtils\\": "lib/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "SimpleSAML\\Test\\TestUtils\\": "tests/src/"
+        }
+    },
     "require": {
+        "php": "^8.1",
+        "ext-curl": "*",
+
         "phpunit/phpunit": "^10.0 || ^11.0",
+        "psr/log": "^2.0 || ^3.0",
         "slevomat/coding-standard": "^8.15",
         "symfony/phpunit-bridge": "^6.4 || ^7.0"
     },
     "require-dev": {
-        "php": "^8.1",
-        "ext-curl": "*",
-
         "simplesamlphp/simplesamlphp": "^2.2.0"
     },
     "support": {
diff --git a/lib/InMemoryStore.php b/lib/InMemoryStore.php
new file mode 100644
index 0000000..05fec37
--- /dev/null
+++ b/lib/InMemoryStore.php
@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\TestUtils;
+
+use SimpleSAML\Store\StoreInterface;
+use SimpleSAML\Utils\ClearableState;
+
+use function array_key_exists;
+
+/**
+ * Class InMemoryStore. Used for testing SSP code.
+ *
+ * Use it by setting `'store.type'` in config.php to this clas
+ */
+class InMemoryStore implements ClearableState, StoreInterface
+{
+    private static array $store = [];
+
+
+    /**
+     * Retrieve a value from the data store.
+     *
+     * @param string $type The data type.
+     * @param string $key The key.
+     *
+     * @return mixed|null The value.
+     */
+    public function get(string $type, string $key): mixed
+    {
+        if (array_key_exists($key, self::$store)) {
+            $item = self::$store[$key];
+            if (isset($item['expire']) && $item['expire'] < time()) {
+                $this->delete($type, $key);
+                return null;
+            }
+            return $item['value'];
+        }
+        return null;
+    }
+
+
+    /**
+     * Save a value to the data store.
+     *
+     * @param string $type The data type.
+     * @param string $key The key.
+     * @param mixed $value The value.
+     * @param int|null $expire The expiration time (unix timestamp), or null if it never expires.
+     */
+    public function set(string $type, string $key, mixed $value, ?int $expire = null): void
+    {
+        self::$store[$key] = [
+            'type' => $type,
+            'value' => $value,
+            'expire' => $expire
+        ];
+    }
+
+
+    /**
+     * Delete a value from the data store.
+     *
+     * @param string $type The data type.
+     * @param string $key The key.
+     */
+    public function delete(string $type, string $key): void
+    {
+        unset(self::$store[$key]);
+    }
+
+
+    /**
+     * Clear any cached internal state.
+     */
+    public static function clearInternalState(): void
+    {
+        self::$store = [];
+    }
+}
diff --git a/phpcs-simplesamlphp.xml b/phpcs-simplesamlphp.xml
index 20925bf..8801d71 100644
--- a/phpcs-simplesamlphp.xml
+++ b/phpcs-simplesamlphp.xml
@@ -17,4 +17,7 @@
 
   <!-- Enforce alphabetically sorted use-statements -->
   <rule ref="SlevomatCodingStandard.Namespaces.AlphabeticallySortedUses" />
+
+  <!-- Enforce the use of trailing commas -->
+  <rule ref="SlevomatCodingStandard.Arrays.TrailingArrayComma" />
 </ruleset>
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..6971499
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" bootstrap="tests/bootstrap.php" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd" cacheDirectory=".phpunit.cache">
+  <coverage>
+    <report>
+      <clover outputFile="build/logs/clover.xml"/>
+      <html outputDirectory="build/coverage" lowUpperBound="35" highLowerBound="70"/>
+      <text outputFile="php://stdout" showUncoveredFiles="true"/>
+    </report>
+  </coverage>
+  <testsuites>
+    <testsuite name="The project's test suite">
+      <directory>./tests</directory>
+    </testsuite>
+  </testsuites>
+  <logging/>
+  <source>
+    <include>
+      <directory suffix=".php">./lib</directory>
+      <directory suffix=".php">./src</directory>
+    </include>
+  </source>
+</phpunit>
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
new file mode 100644
index 0000000..28c2413
--- /dev/null
+++ b/tests/bootstrap.php
@@ -0,0 +1,6 @@
+<?php
+
+declare(strict_types=1);
+
+$projectRoot = dirname(__DIR__);
+require_once($projectRoot . '/vendor/autoload.php');
diff --git a/tests/src/InMemoryStoreTest.php b/tests/src/InMemoryStoreTest.php
new file mode 100644
index 0000000..53ba4bb
--- /dev/null
+++ b/tests/src/InMemoryStoreTest.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Test\TestUtils;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\Configuration;
+use SimpleSAML\Store\StoreFactory;
+use SimpleSAML\TestUtils\InMemoryStore;
+
+use function sleep;
+use function time;
+
+#[CoversClass(InMemoryStore::class)]
+class InMemoryStoreTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        InMemoryStore::clearInternalState();
+        Configuration::clearInternalState();
+    }
+
+
+    public function testState(): void
+    {
+        // given: an SSP config that overrides the store type
+        $config = [
+            'store.type' => 'SimpleSAML\TestUtils\InMemoryStore',
+        ];
+        Configuration::loadFromArray($config, '[ARRAY]', 'simplesaml');
+
+        // when: getting the store
+        $store = StoreFactory::getInstance('SimpleSAML\TestUtils\InMemoryStore');
+
+        // then: will give us the right type of store
+        $this->assertInstanceOf(InMemoryStore::class, $store);
+
+        // and: we can store stuff
+        $this->assertNull($store->get('string', 'key'), 'Key does not exist yet');
+        $store->set('string', 'key', 'value');
+        $this->assertEquals('value', $store->get('string', 'key'));
+        $store->delete('string', 'key');
+        $this->assertNull($store->get('string', 'key'), 'Key was removed');
+    }
+
+
+    public function testExpiration(): void
+    {
+        $store = new InMemoryStore();
+        $store->set('string', 'key', 'value', time() + 1);
+        $this->assertEquals('value', $store->get('string', 'key'));
+        $this->assertEquals('value', $store->get('string', 'key'));
+        sleep(2);
+        $this->assertNull($store->get('string', 'key'));
+    }
+}
diff --git a/tools/composer-require-checker.json b/tools/composer-require-checker.json
new file mode 100644
index 0000000..eed71aa
--- /dev/null
+++ b/tools/composer-require-checker.json
@@ -0,0 +1,4 @@
+{
+  "symbol-whitelist": [
+  ]
+}