diff --git a/.config/.remarkrc b/.config/.remarkrc
new file mode 100644
index 0000000..bfa065d
--- /dev/null
+++ b/.config/.remarkrc
@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "remark-preset-lint-recommended",
+    ["remark-lint-list-item-indent", "space"]
+  ]
+}
diff --git a/.config/.yamllint b/.config/.yamllint
new file mode 100644
index 0000000..7c1b6e4
--- /dev/null
+++ b/.config/.yamllint
@@ -0,0 +1,14 @@
+---
+extends: default
+
+ignore: |
+  vendor/
+
+rules:
+  brackets:
+    max-spaces-inside: 1
+  document-start: disable
+  line-length:
+    level: warning
+    max: 120
+  truthy: {allowed-values: ["true", "false", "on"]}
diff --git a/.github/workflows/json.yml b/.github/workflows/json.yml
new file mode 100644
index 0000000..7e83269
--- /dev/null
+++ b/.github/workflows/json.yml
@@ -0,0 +1,46 @@
+---
+name: JSON Quality Assistance
+
+on:
+  # This event occurs when there is activity on a pull request. The workflow
+  # will be run against the commits, after merge to the target branch (main).
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.json'
+      - '.github/workflows/json.yml'
+    types: [ opened, reopened, synchronize ]
+  # This event occurs when there is a push to the repository.
+  push:
+    paths:
+      - '**.json'
+      - '.github/workflows/json.yml'
+  # Allow manually triggering the workflow.
+  workflow_dispatch:
+
+# Cancels all previous workflow runs for the same branch that have not yet completed.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  # Needed to allow the "concurrency" section to cancel a workflow run.
+  actions: write
+
+jobs:
+  # 01.preflight.json.lint-syntax.yml
+  lint-json-syntax:
+    name: JSON Syntax Linting
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker://pipelinecomponents/jsonlint
+        with:
+          args: >-
+            find .
+            -not -path '*/.git/*'
+            -not -path '*/node_modules/*'
+            -not -path '*/vendor/*'
+            -name '*.json'
+            -type f
+            -exec jsonlint --quiet {} ;
diff --git a/.github/workflows/markdown.yml b/.github/workflows/markdown.yml
new file mode 100644
index 0000000..581b9c7
--- /dev/null
+++ b/.github/workflows/markdown.yml
@@ -0,0 +1,42 @@
+---
+name: Markdown Quality Assistance
+
+on:
+  # This event occurs when there is activity on a pull request. The workflow
+  # will be run against the commits, after merge to the target branch (main).
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.md'
+      - '.github/workflows/markdown.yml'
+    types: [ opened, reopened, synchronize ]
+  # This event occurs when there is a push to the repository.
+  push:
+    paths:
+      - '**.md'
+      - '.github/workflows/markdown.yml'
+  # Allow manually triggering the workflow.
+  workflow_dispatch:
+
+# Cancels all previous workflow runs for the same branch that have not yet completed.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  # Needed to allow the "concurrency" section to cancel a workflow run.
+  actions: write
+
+jobs:
+  # 01.quality.markdown.lint-syntax.yml
+  lint-markdown-syntax:
+    name: Markdown Linting
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker://pipelinecomponents/remark-lint
+        with:
+          args: >-
+            remark
+            --rc-path=.config/.remarkrc
+            --ignore-pattern='*/vendor/*'
diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
new file mode 100644
index 0000000..85c820c
--- /dev/null
+++ b/.github/workflows/php.yml
@@ -0,0 +1,134 @@
+---
+name: PHP Quality Assistance
+
+on:
+  # This event occurs when there is activity on a pull request. The workflow
+  # will be run against the commits, after merge to the target branch (main).
+  pull_request:
+    paths:
+      - '**.php'
+      - '.config/phpcs.xml.dist'
+      - 'tests/phpunit/phpunit.xml'
+      - '.github/workflows/php.yml'
+      - 'composer.json'
+      - 'composer.lock'
+    branches: [ main, feature/php-ci ]
+    types: [ opened, reopened, synchronize ]
+  # This event occurs when there is a push to the repository.
+  push:
+    paths:
+      - '**.php'
+      - '.config/phpcs.xml.dist'
+      - 'tests/phpunit/phpunit.xml'
+      - '.github/workflows/php.yml'
+      - 'composer.json'
+      - 'composer.lock'
+  # Allow manually triggering the workflow.
+  workflow_dispatch:
+
+
+# Cancels all previous workflow runs for the same branch that have not yet completed.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  # Needed to allow the "concurrency" section to cancel a workflow run.
+  actions: write
+
+jobs:
+  # 01.preflight.php.lint-syntax.yml
+  lint-php-syntax:
+    name: PHP Syntax Linting
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker://pipelinecomponents/php-linter
+        with:
+          args: >-
+            parallel-lint
+            --exclude .git
+            --exclude vendor
+            --no-progress
+            .
+#  # 01.quality.php.validate.dependencies-file.yml
+  validate-dependencies-file:
+    name: Validate dependencies file
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - run: >-
+            composer validate
+            --check-lock
+            --no-plugins
+            --no-scripts
+            --strict
+  # 02.test.php.test-unit.yml
+  php-unittest:
+    name: PHP Unit Tests
+    needs:
+      - lint-php-syntax
+      - validate-dependencies-file
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        php:
+          - '8.1'  # from 2021-11 to 2023-11 (2025-12)
+          - '8.2'  # from 2022-12 to 2024-12 (2026-12)
+          - '8.3'  # from 2023-11 to 2025-12 (2027-12)
+    steps:
+      - uses: actions/checkout@v4
+      - uses: shivammathur/setup-php@v2
+        with:
+          coverage: xdebug
+          ini-values: error_reporting=E_ALL, display_errors=On
+          php-version: ${{ matrix.php }}
+      - name: Install and Cache Composer dependencies
+        uses: "ramsey/composer-install@v2"
+        env:
+          COMPOSER_AUTH: '{"github-oauth": {"github.com": "${{ secrets.GITHUB_TOKEN }}"}}'
+      - run: vendor/bin/phpunit --configuration tests/phpunit/phpunit.xml
+  # 03.quality.php.scan.dependencies-vulnerabilities.yml
+  scan-dependencies-vulnerabilities:
+    name: Scan Dependencies Vulnerabilities
+    needs:
+      - validate-dependencies-file
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install and Cache Composer dependencies
+        uses: "ramsey/composer-install@v2"
+        env:
+          COMPOSER_AUTH: '{"github-oauth": {"github.com": "${{ secrets.GITHUB_TOKEN }}"}}'
+      - run: >-
+          composer audit
+          --abandoned=report
+          --no-dev
+          --no-plugins
+          --no-scripts
+  # 03.quality.php.lint-version-compatibility.yml
+  php-check-version-compatibility:
+    name: PHP Version Compatibility
+    needs:
+      - lint-php-syntax
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        php:
+          - '8.1'  # from 2021-11 to 2023-11 (2025-12)
+          - '8.2'  # from 2022-12 to 2024-12 (2026-12)
+          - '8.3'  # from 2023-11 to 2025-12 (2027-12)
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker://pipelinecomponents/php-codesniffer
+        with:
+          args: >-
+            phpcs
+            -s
+            --extensions=php
+            --ignore='*vendor/*'
+            --runtime-set testVersion ${{ matrix.php }}
+            --standard=PHPCompatibility
+            .
diff --git a/.github/workflows/yaml.yml b/.github/workflows/yaml.yml
new file mode 100644
index 0000000..ad8fb9d
--- /dev/null
+++ b/.github/workflows/yaml.yml
@@ -0,0 +1,42 @@
+---
+name: YAML Quality Assistance
+
+on:
+  # This event occurs when there is activity on a pull request. The workflow
+  # will be run against the commits, after merge to the target branch (main).
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.yml'
+      - '**.yaml'
+    types: [ opened, reopened, synchronize ]
+  # This event occurs when there is a push to the repository.
+  push:
+    paths:
+      - '**.yml'
+      - '**.yaml'
+  # Allow manually triggering the workflow.
+  workflow_dispatch:
+
+# Cancels all previous workflow runs for the same branch that have not yet completed.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  # Needed to allow the "concurrency" section to cancel a workflow run.
+  actions: write
+
+jobs:
+  # 01.preflight.yaml.lint.yml
+  lint-yaml:
+    name: YAML Linting
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker://pipelinecomponents/yamllint
+        with:
+          args: >-
+            yamllint
+            --config-file=.config/.yamllint
+            .
diff --git a/TODO b/TODO
index fb86193..0e4659a 100644
--- a/TODO
+++ b/TODO
@@ -57,4 +57,21 @@
 - [v] webid
 - [v] wac
 - [v] solid-crud
-- [v] CI integration
\ No newline at end of file
+- [v] CI integration
+
+------ Unit tests -----
+- [v] ClientRegistration
+- [v] JtiStore
+- [v] IpAttempts
+- [v] Util
+- [v] PasswordValidator
+- [ ] Mailer
+- [ ] MailTemplateGenerator
+- [ ] MailTemplates
+- [ ] Server
+- [ ] SolidNotifications
+- [ ] SolidPubSub
+- [ ] StorageServer
+- [ ] User
+- [-] Middleware
+- [-] Db
diff --git a/composer.json b/composer.json
index d0e1836..1b4d9e0 100644
--- a/composer.json
+++ b/composer.json
@@ -1,5 +1,6 @@
 {
     "name": "pdsinterop/php-solid",
+    "description": "Multi-user Solid Server for PHP",
     "type": "project",
     "license": "MIT",
     "autoload": {
@@ -17,12 +18,12 @@
         "pdsinterop/solid-auth": "v0.13.0",
         "pdsinterop/solid-crud": "v0.8.1",
         "phpmailer/phpmailer": "^6.10",
-        "sweetrdf/easyrdf": "v1.15",
+        "sweetrdf/easyrdf": "~1.15.0",
         "phpseclib/bcmath_compat": "^2.0",
         "phrity/websocket": "^3.5"
     },
     "require-dev": {
-        "phpunit/phpunit": "^12.2",
+        "phpunit/phpunit": "^9 || ^10 || ^11 || ^12",
         "phpstan/phpstan": "^2.1"
     }
 }
diff --git a/init.php b/init.php
index 8bdba37..52d3d89 100644
--- a/init.php
+++ b/init.php
@@ -32,7 +32,7 @@ function initDatabase() {
 		    )',
 		    'CREATE TABLE IF NOT EXISTS jti (
 			jti VARCHAR(255) NOT NULL PRIMARY KEY,
-			expires TEXT
+			expires TEXT NOT NULL
 		    )',
 		    'CREATE TABLE IF NOT EXISTS users (
 			user_id VARCHAR(255) NOT NULL PRIMARY KEY,
@@ -43,7 +43,7 @@ function initDatabase() {
 		    'CREATE TABLE IF NOT EXISTS ipAttempts (
 			ip VARCHAR(255) NOT NULL,
 			type VARCHAR(255) NOT NULL,
-			expires NOT NULL
+			expires TEXT NOT NULL
 		    )',
 		];
 		      
diff --git a/lib/ClientRegistration.php b/lib/ClientRegistration.php
index a0c354c..88d98a0 100644
--- a/lib/ClientRegistration.php
+++ b/lib/ClientRegistration.php
@@ -1,17 +1,12 @@
 <?php
 	namespace Pdsinterop\PhpSolid;
-	
+
+	use Pdsinterop\PhpSolid\Db;
+
 	class ClientRegistration {
-		private static $pdo;
-		private static function connect() {
-			if (!isset(self::$pdo)) {
-				self::$pdo = new \PDO("sqlite:" . DBPATH);
-			}
-		}
-			
 		public static function getRegistration($clientId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT clientData FROM clients WHERE clientId=:clientId'
 			);
 			$query->execute([
@@ -25,11 +20,11 @@ public static function getRegistration($clientId) {
 		}
 		
 		public static function saveClientRegistration($clientData) {
-			self::connect();
+			Db::connect();
 			if (!isset($clientData['client_name'])) {
 				$clientData['client_name'] = $clientData['origin'];
 			}
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'INSERT INTO clients VALUES(:clientId, :origin, :clientData)'
 			);
 			$query->execute([
@@ -40,8 +35,8 @@ public static function saveClientRegistration($clientData) {
 		}
 		
 		public static function getClientByOrigin($origin) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT clientData FROM clients WHERE origin=:origin'
 			);
 			$query->execute([
diff --git a/lib/Db.php b/lib/Db.php
new file mode 100644
index 0000000..8eb46e1
--- /dev/null
+++ b/lib/Db.php
@@ -0,0 +1,11 @@
+<?php
+	namespace Pdsinterop\PhpSolid;
+	
+	class Db {
+		public static $pdo;
+		public static function connect() {
+			if (!isset(self::$pdo)) {
+				self::$pdo = new \PDO("sqlite:" . DBPATH);
+			}
+		}
+	}
diff --git a/lib/IpAttempts.php b/lib/IpAttempts.php
index 09b5c1b..360031e 100644
--- a/lib/IpAttempts.php
+++ b/lib/IpAttempts.php
@@ -1,22 +1,17 @@
 <?php
 	namespace Pdsinterop\PhpSolid;
-	
-	class IpAttempts {
-		private static $pdo;
-		private static function connect() {
-			if (!isset(self::$pdo)) {
-				self::$pdo = new \PDO("sqlite:" . DBPATH);
-			}
-		}
 
+	use Pdsinterop\PhpSolid\Db;
+
+	class IpAttempts {
 		public static function logFailedAttempt($ip, $type, $expires) {
 			if (in_array($ip, TRUSTED_IPS)) {
 				return;
 			}
 
-			self::connect();
+			Db::connect();
 			
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'INSERT INTO ipAttempts VALUES(:ip, :type, :expires)'
 			);
 			$query->execute([
@@ -31,10 +26,10 @@ public static function getAttemptsCount($ip, $type) {
 				return 0;
 			}
 
-			self::connect();
+			Db::connect();
 
 			$now = new \DateTime();
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'SELECT count(ip) as count FROM ipAttempts WHERE ip=:ip AND type=:type AND expires > :now'
 			);
 			$query->execute([
@@ -49,10 +44,10 @@ public static function getAttemptsCount($ip, $type) {
 			return 0;
 		}
 		public static function cleanupAttempts() {
-			self::connect();
+			Db::connect();
 			
 			$now = new \DateTime();
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'DELETE FROM ipAttempts WHERE expires < :now'
 			);
 			$query->execute([
diff --git a/lib/JtiStore.php b/lib/JtiStore.php
index bbf7861..b487059 100644
--- a/lib/JtiStore.php
+++ b/lib/JtiStore.php
@@ -1,19 +1,12 @@
 <?php
 	namespace Pdsinterop\PhpSolid;
-	
+
+	use Pdsinterop\PhpSolid\Db;
 	class JtiStore {
-		private static $pdo;
-		private static function connect() {
-			if (!isset(self::$pdo)) {
-				self::$pdo = new \PDO("sqlite:" . DBPATH);
-			}
-		}
-			
 		public static function hasJti($jti) {
-			self::connect();
+			Db::connect();
 			$now = new \DateTime();
-			
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'SELECT jti FROM jti WHERE jti=:jti AND expires>:now'
 			);
 			$query->execute([
@@ -28,8 +21,8 @@ public static function hasJti($jti) {
 		}
 		
 		public static function saveJti($jti) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'INSERT INTO jti VALUES(:jti, :expires)'
 			);
 			$expires = new \DateTime();
@@ -39,4 +32,15 @@ public static function saveJti($jti) {
 				':expires' => $expires->getTimestamp()
 			]);
 		}
+
+		public static function cleanupJti() {
+			Db::connect();
+			$now = new \DateTime();
+			$query = Db::$pdo->prepare(
+				'DELETE FROM jti WHERE expires < :now'
+			);
+			$query->execute([
+				':now' => $now->getTimestamp()
+			]);
+		}
 	}
\ No newline at end of file
diff --git a/lib/User.php b/lib/User.php
index 66c5505..22a2527 100644
--- a/lib/User.php
+++ b/lib/User.php
@@ -2,15 +2,9 @@
 	namespace Pdsinterop\PhpSolid;
 
 	use Pdsinterop\PhpSolid\PasswordValidator;
-
+	use Pdsinterop\PhpSolid\Db;
+	
 	class User {
-		private static $pdo;
-                private static function connect() {
-                        if (!isset(self::$pdo)) {
-                                self::$pdo = new \PDO("sqlite:" . DBPATH);
-                        }
-                }
-
 		private static function generateTokenCode() {
 			$digits = 6;
 			$code = random_int(0,1000000);
@@ -42,8 +36,8 @@ public static function saveVerifyToken($tokenType, $tokenData) {
 				break;
 			}
 
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'INSERT INTO verify VALUES(:code, :data)'
 			);
 			$query->execute([
@@ -54,8 +48,8 @@ public static function saveVerifyToken($tokenType, $tokenData) {
 		}
 		
 		public static function getVerifyToken($code) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT data FROM verify WHERE code=:code'
 			);
 			$query->execute([
@@ -84,13 +78,14 @@ public static function validatePasswordStrength($password) {
 			$entropy = PasswordValidator::getEntropy($password, BANNED_PASSWORDS);
 			$minimumEntropy = MINIMUM_PASSWORD_ENTROPY;
 			if ($entropy < $minimumEntropy) {
+				error_log("Entered pasword does not satisfy minimum entropy");
 				return false;
 			}
 			return true;
 		}
 
 		public static function createUser($newUser) {
-			self::connect();
+			Db::connect();
 			if (!self::validatePasswordStrength($newUser['password'])) {
 				return false;
 			}
@@ -98,7 +93,7 @@ public static function createUser($newUser) {
 			while (self::userIdExists($generatedUserId)) {
 				$generatedUserId = md5(random_bytes(32));
 			}
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				 'INSERT INTO users VALUES (:userId, :email, :passwordHash, :data)'
 			);
 			
@@ -126,8 +121,8 @@ public static function setUserPassword($email, $newPassword) {
 			if (!self::validatePasswordStrength($newPassword)) {
 				return false;
 			}
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				 'UPDATE users SET password=:passwordHash WHERE email=:email'
 			);
 			$queryParams = [];
@@ -139,8 +134,8 @@ public static function setUserPassword($email, $newPassword) {
 		}
 
 		public static function allowClientForUser($clientId, $userId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'INSERT OR REPLACE INTO allowedClients VALUES(:userId, :clientId)'
 			);
 			$query->execute([
@@ -151,8 +146,8 @@ public static function allowClientForUser($clientId, $userId) {
 		}
 
 		public static function getAllowedClients($userId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT clientId FROM allowedClients WHERE userId=:userId'
 			);
 			$query->execute([
@@ -166,8 +161,8 @@ public static function getAllowedClients($userId) {
 		}
 
 		public static function getStorage($userId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT storageUrl FROM userStorage WHERE userId=:userId'
 			);
 			$query->execute([
@@ -181,8 +176,8 @@ public static function getStorage($userId) {
 		}
 
 		public static function setStorage($userId, $storageUrl) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'INSERT OR REPLACE INTO storage VALUES(:userId, :storageUrl)'
 			);
 			$query->execute([
@@ -192,8 +187,8 @@ public static function setStorage($userId, $storageUrl) {
 		}
 
 		public static function getUser($email) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT user_id, data FROM users WHERE email=:email'
 			);
 			$query->execute([
@@ -217,8 +212,8 @@ public static function getUser($email) {
 		}
 
 		public static function getUserById($userId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT user_id, data FROM users WHERE user_id=:userId'
 			);
 			$query->execute([
@@ -242,8 +237,8 @@ public static function getUserById($userId) {
 		}
 
 		public static function checkPassword($email, $password) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT password FROM users WHERE email=:email'
 			);
 			$query->execute([
@@ -271,8 +266,8 @@ public static function getLoggedInUser() {
 		}
 
 		public static function userIdExists($userId) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT user_id FROM users WHERE user_id=:userId'
 			);
 			$query->execute([
@@ -286,8 +281,8 @@ public static function userIdExists($userId) {
 		}
 
 		public static function userEmailExists($email) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'SELECT user_id FROM users WHERE email=:email'
 			);
 			$query->execute([
@@ -301,8 +296,8 @@ public static function userEmailExists($email) {
 		}
 
 		private static function deleteUser($email) {
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'DELETE FROM users WHERE email=:email'
 			);
 			$query->execute([
@@ -316,8 +311,8 @@ private static function deleteAllowedClients($email) {
 				return;
 			}
 
-			self::connect();
-			$query = self::$pdo->prepare(
+			Db::connect();
+			$query = Db::$pdo->prepare(
 				'DELETE FROM allowedClients WHERE userId=:userId'
 			);
 			$query->execute([
@@ -335,10 +330,10 @@ public static function deleteAccount($email) {
 		}
 
 		public static function cleanupTokens() {
-			self::connect();
+			Db::connect();
 
 			$now = new \DateTime();
-			$query = self::$pdo->prepare(
+			$query = Db::$pdo->prepare(
 				'DELETE FROM verify WHERE json_extract(data, \'$.expires\') < :now'
 			);
 			$query->execute([
diff --git a/tests/phpunit/ClientRegistrationTest.php b/tests/phpunit/ClientRegistrationTest.php
new file mode 100644
index 0000000..8616fde
--- /dev/null
+++ b/tests/phpunit/ClientRegistrationTest.php
@@ -0,0 +1,74 @@
+<?php
+namespace Pdsinterop\PhpSolid\Tests;
+
+require_once(__DIR__ . "/test-config.php");
+
+use Pdsinterop\PhpSolid\ClientRegistration;
+use Pdsinterop\PhpSolid\Db;
+
+class ClientRegistrationTest extends \PHPUnit\Framework\TestCase
+{
+    protected function setUp(): void
+    {
+        $statements = [
+            'DROP TABLE IF EXISTS clients',
+            'CREATE TABLE clients (
+                clientId VARCHAR(255) NOT NULL PRIMARY KEY,
+                origin TEXT NOT NULL,
+                clientData TEXT NOT NULL
+            )'
+        ];
+
+        Db::connect();
+        try {
+            // create tables
+            foreach($statements as $statement){
+                Db::$pdo->exec($statement);
+            }
+        } catch(\PDOException $e) {
+            echo $e->getMessage();
+        }
+
+        ClientRegistration::saveClientRegistration([
+            "client_id" => "12345",
+            "origin" => "https://example.com",
+            "client_name" => "Client name"
+        ]);
+
+        ClientRegistration::saveClientRegistration([
+            "client_id" => "23456",
+            "origin" => "https://example2.com"
+        ]);
+
+        ClientRegistration::saveClientRegistration([
+            "client_id" => "34567",
+            "origin" => "https://example2.com"
+        ]);
+    }
+
+    public function testGetRegistration() {
+        $storedData = ClientRegistration::getRegistration("12345");
+        $this->assertEquals("12345", $storedData['client_id']);
+        $this->assertEquals("https://example.com", $storedData['origin']);
+        $this->assertEquals("Client name", $storedData['client_name']);
+    }
+
+    public function testClientNameAutofill() {
+        $storedData = ClientRegistration::getRegistration("23456");
+        $this->assertEquals("23456", $storedData['client_id']);
+        $this->assertEquals("https://example2.com", $storedData['origin']);
+        $this->assertEquals("https://example2.com", $storedData['client_name']);
+    }
+
+    public function testClientByOrigin() {
+        $storedData = ClientRegistration::getClientByOrigin("https://example.com");
+        $this->assertEquals("12345", $storedData['client_id']);
+        $this->assertEquals("https://example.com", $storedData['origin']);
+        $this->assertEquals("Client name", $storedData['client_name']);
+    }
+
+    public function testClientByDuplicateOrigin() {
+        $storedData = ClientRegistration::getClientByOrigin("https://example2.com");
+        $this->assertFalse($storedData); // false because we have 2 clients with the same origin
+    }
+}
diff --git a/tests/phpunit/IpAttemptsTest.php b/tests/phpunit/IpAttemptsTest.php
new file mode 100644
index 0000000..df0373d
--- /dev/null
+++ b/tests/phpunit/IpAttemptsTest.php
@@ -0,0 +1,123 @@
+<?php
+namespace Pdsinterop\PhpSolid\Tests;
+
+require_once(__DIR__ . "/test-config.php");
+
+use Pdsinterop\PhpSolid\IpAttempts;
+use Pdsinterop\PhpSolid\Db;
+
+class IpAttemptsTest extends \PHPUnit\Framework\TestCase
+{
+    protected function setUp(): void
+    {
+        $statements = [
+            'DROP TABLE IF EXISTS ipAttempts',
+	    'CREATE TABLE IF NOT EXISTS ipAttempts (
+		ip VARCHAR(255) NOT NULL,
+		type VARCHAR(255) NOT NULL,
+		expires NOT NULL
+	    )'
+        ];
+
+        Db::connect();
+        try {
+            // create tables
+            foreach($statements as $statement){
+                Db::$pdo->exec($statement);
+            }
+        } catch(\PDOException $e) {
+            echo $e->getMessage();
+        }
+    }
+
+    public function testGetAttemptsCountZero() {
+        $ip = "10.0.0.1";
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(0, $count);
+    }
+
+    public function testGetAttemptsCountOne() {
+        $ip = "10.0.0.1";
+        
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(1, $count);
+    }
+
+    public function testGetAttemptsCountTwo() {
+        $ip = "10.0.0.1";
+        
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(2, $count);
+    }
+
+    public function testGetAttemptsCountExpired() {
+        $ip = "10.0.0.1";
+        
+        IpAttempts::logFailedAttempt($ip, "test", time() - 1);
+        IpAttempts::logFailedAttempt($ip, "test", time() - 1);
+
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(0, $count);
+    }
+
+    public function testGetAttemptsCountOneExpired() {
+        $ip = "10.0.0.1";
+        
+        IpAttempts::logFailedAttempt($ip, "test", time() + 10);
+        IpAttempts::logFailedAttempt($ip, "test", time() - 1);
+
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(1, $count);
+    }
+
+    public function testCleanup() {
+        $ip = "10.0.0.1";
+        
+        IpAttempts::logFailedAttempt($ip, "test", time() - 1);
+        IpAttempts::logFailedAttempt($ip, "test", time() - 1);
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+
+        $query = Db::$pdo->prepare('SELECT count(*) AS count FROM ipAttempts');
+        $query->execute();
+        $result = $query->fetchAll();
+        $beforeCleanup = $result[0]['count'];
+
+        $this->assertEquals(4, $beforeCleanup);
+        
+        IpAttempts::cleanupAttempts();
+        $query = Db::$pdo->prepare('SELECT count(*) AS count FROM ipAttempts');
+        $query->execute();
+        $result = $query->fetchAll();
+        $afterCleanup = $result[0]['count'];
+
+        $this->assertEquals(2, $afterCleanup);
+    }
+
+    public function testTrustedIpGetAttempts() {
+        $ip = "127.0.0.100"; // trusted IP
+
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+
+        $count = IpAttempts::getAttemptsCount($ip, "test");
+        $this->assertEquals(0, $count);
+    }
+
+    public function testTrustedIpGetAttemptsSkipsDb() {
+        $ip = "127.0.0.100"; // trusted IP
+
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+        IpAttempts::logFailedAttempt($ip, "test", time() + 3600);
+
+        $query = Db::$pdo->prepare('SELECT count(*) AS count FROM ipAttempts');
+        $query->execute();
+        $result = $query->fetchAll();
+        $count = $result[0]['count'];
+        $this->assertEquals(0, $count);
+    }
+}
diff --git a/tests/phpunit/JtiStoreTest.php b/tests/phpunit/JtiStoreTest.php
new file mode 100644
index 0000000..602afa4
--- /dev/null
+++ b/tests/phpunit/JtiStoreTest.php
@@ -0,0 +1,87 @@
+<?php
+namespace Pdsinterop\PhpSolid\Tests;
+
+require_once(__DIR__ . "/test-config.php");
+
+use Pdsinterop\PhpSolid\JtiStore;
+use Pdsinterop\PhpSolid\Db;
+
+class JtiStoreTest extends \PHPUnit\Framework\TestCase
+{
+    protected function setUp(): void
+    {
+        $statements = [
+            'DROP TABLE IF EXISTS jti',
+	    'CREATE TABLE IF NOT EXISTS jti (
+		jti VARCHAR(255) NOT NULL PRIMARY KEY,
+		expires TEXT
+	    )'
+        ];
+
+        Db::connect();
+        try {
+            // create tables
+            foreach($statements as $statement){
+                Db::$pdo->exec($statement);
+            }
+        } catch(\PDOException $e) {
+            echo $e->getMessage();
+        }
+    }
+
+    public function testNonExistingJti() {
+        $jti = "123";
+        $found = JtiStore::hasJti($jti);
+        $this->assertFalse($found);
+    }
+
+    public function testExistingJti() {
+        $jti = "123";
+        JtiStore::saveJti($jti, time() + 3600);
+        $found = JtiStore::hasJti($jti);
+        $this->assertTrue($found);
+    }
+
+    public function testExpiredJti() {
+        $jti = "123";
+        JtiStore::saveJti($jti);
+        $query = Db::$pdo->prepare('UPDATE jti SET expires=:expires WHERE jti=:jti');
+        $query->execute([
+            'expires' => time() - 10,
+            'jti' => $jti
+        ]);
+        $found = JtiStore::hasJti($jti);
+        $this->assertFalse($found);
+    }
+
+    public function testCleanup() {
+        JtiStore::saveJti("123");
+        JtiStore::saveJti("234");
+
+        $query = Db::$pdo->prepare('UPDATE jti SET expires=:expires WHERE jti=:jti');
+        $query->execute([
+            'expires' => time() - 10,
+            'jti' => "123"
+        ]);
+        $query = Db::$pdo->prepare('UPDATE jti SET expires=:expires WHERE jti=:jti');
+        $query->execute([
+            'expires' => time() - 10,
+            'jti' => "234"
+        ]);
+
+        $query = Db::$pdo->prepare('SELECT count(*) AS count FROM jti');
+        $query->execute();
+        $result = $query->fetchAll();
+        $beforeCleanup = $result[0]['count'];
+        $this->assertEquals(2, $beforeCleanup);
+
+        
+        JtiStore::cleanupJti();
+        $query = Db::$pdo->prepare('SELECT count(*) AS count FROM jti');
+        $query->execute();
+        $result = $query->fetchAll();
+        $afterCleanup = $result[0]['count'];
+
+        $this->assertEquals(0, $afterCleanup);
+    }
+}
diff --git a/tests/phpunit/PasswordValidatorTest.php b/tests/phpunit/PasswordValidatorTest.php
new file mode 100644
index 0000000..9930219
--- /dev/null
+++ b/tests/phpunit/PasswordValidatorTest.php
@@ -0,0 +1,79 @@
+<?php
+namespace Pdsinterop\PhpSolid\Tests;
+
+use Pdsinterop\PhpSolid\PasswordValidator;
+
+class PasswordValidatorTest extends \PHPUnit\Framework\TestCase
+{
+    public function testBaseLower()
+    {
+        $password = "aaa";
+        $this->assertEquals(26, PasswordValidator::getBase($password));
+    }
+
+    public function testBaseUpper()
+    {
+        $password = "AAA";
+        $this->assertEquals(26, PasswordValidator::getBase($password));
+    }
+
+    public function testBaseNumbers()
+    {
+        $password = "123";
+        $this->assertEquals(10, PasswordValidator::getBase($password));
+    }
+
+    public function testBaseSpecial()
+    {
+        $password = "!@#$";
+        $this->assertEquals(32, PasswordValidator::getBase($password));
+    }
+
+    public function testBaseUpperAndLower()
+    {
+        $password = "aaaAAA";
+        $this->assertEquals(52, PasswordValidator::getBase($password));
+    }
+
+    public function testLengthLower()
+    {
+        $password = "aaa";
+        $this->assertEquals(2, PasswordValidator::getLength($password));
+    }
+
+    public function testLengthUpper()
+    {
+        $password = "AAA";
+        $this->assertEquals(2, PasswordValidator::getLength($password));
+    }
+
+    public function testLengthNumbers()
+    {
+        $password = "123";
+        $this->assertEquals(3, PasswordValidator::getLength($password));
+    }
+
+    public function testLengthSpecial()
+    {
+        $password = "!@#$";
+        $this->assertEquals(4, PasswordValidator::getLength($password));
+    }
+
+    public function testLengthUpperAndLower()
+    {
+        $password = "aaaAAA";
+        $this->assertEquals(4, PasswordValidator::getLength($password));
+    }
+
+    public function testSimplyEntropy()
+    {
+        $values = [
+            ["password" => "aaa", "expected" => 6.52],
+            ["password" => "abc", "expected" => 9.77]
+        ];
+
+        foreach ($values as $value) {
+            $this->assertEquals($value['expected'], PasswordValidator::getEntropy($value['password']));
+        }
+    }
+}
diff --git a/tests/phpunit/UtilTest.php b/tests/phpunit/UtilTest.php
new file mode 100644
index 0000000..c92b71b
--- /dev/null
+++ b/tests/phpunit/UtilTest.php
@@ -0,0 +1,14 @@
+<?php
+namespace Pdsinterop\PhpSolid\Tests;
+
+use Pdsinterop\PhpSolid\Util;
+
+class UtilTest extends \PHPUnit\Framework\TestCase
+{
+    public function testBase64EncodeDecode() {
+        $string = "this is a test string with more stuffing";
+        $encoded = Util::base64_url_encode($string);
+        $decoded = Util::base64_url_decode($encoded);
+        $this->assertEquals($string, $decoded);
+    }
+}
diff --git a/tests/phpunit/phpunit.xml b/tests/phpunit/phpunit.xml
new file mode 100644
index 0000000..e883c5d
--- /dev/null
+++ b/tests/phpunit/phpunit.xml
@@ -0,0 +1,7 @@
+<phpunit colors="true">
+    <testsuites>
+        <testsuite name="unit">
+            <directory>.</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/tests/phpunit/test-config.php b/tests/phpunit/test-config.php
new file mode 100644
index 0000000..c917c6c
--- /dev/null
+++ b/tests/phpunit/test-config.php
@@ -0,0 +1,5 @@
+<?php
+namespace Pdsinterop\PhpSolid;
+
+const DBPATH = ":memory:";
+const TRUSTED_IPS = ['127.0.0.100'];
diff --git a/www/idp/index.php b/www/idp/index.php
index dec7c29..ca611d6 100644
--- a/www/idp/index.php
+++ b/www/idp/index.php
@@ -12,6 +12,7 @@
 	use Pdsinterop\PhpSolid\User;
 	use Pdsinterop\PhpSolid\Mailer;
 	use Pdsinterop\PhpSolid\IpAttempts;
+	use Pdsinterop\PhpSolid\JtiStore;
 
 	$request = explode("?", $_SERVER['REQUEST_URI'], 2)[0];
 	$method = $_SERVER['REQUEST_METHOD'];
@@ -198,18 +199,22 @@
 				case "/api/accounts/new/":
 					$verifyToken = User::getVerifyToken($_POST['confirm']);
 					if (!$verifyToken) {
+						error_log("No verify token sent");
 						header("HTTP/1.1 400 Bad Request");
 						exit();
 					}
 					if ($verifyToken['email'] !== $_POST['email']) {
+						error_log("Verify token does not match email");
 						header("HTTP/1.1 400 Bad Request");
 						exit();
 					}
 					if (User::userEmailExists($_POST['email'])) {
+						error_log("Account already exists");
 						header("HTTP/1.1 400 Bad Request");
 						exit();
 					}
 					if (!$_POST['password'] === $_POST['repeat_password']) {
+						error_log("Password repeat does not match");
 						header("HTTP/1.1 400 Bad Request");
 						exit();
 					}
@@ -221,6 +226,7 @@
 
 					$createdUser = User::createUser($newUser);
 					if (!$createdUser) {
+						error_log("Failed to create user");
 						header("HTTP/1.1 400 Bad Request");
 						exit();
 					}
@@ -427,6 +433,7 @@
 				touch(CLEANUP_FILE, time() + 3600);
 				User::cleanupTokens();
 				IpAttempts::cleanupAttempts();
+				JtiStore::cleanupJti();
 			}
 		break;
 		case "OPTIONS":