diff --git a/CHANGELOG.md b/CHANGELOG.md
index f80ee679..3dbf5ed6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/kbsali/php-redmine-api/compare/v2.0.1...v2.x)
 
+### Added
+
+- New interface `Redmine\Exception` that is implemented by every library-related exception
+- New exception `Redmine\Exception\ClientException` for client related exceptions
+- New exception `Redmine\Exception\InvalidApiNameException` if an invalid API instance is requested
+- New exception `Redmine\Exception\InvalidParameterException` for invalid parameter provided to an API instance
+- New exception `Redmine\Exception\MissingParameterException` for missing parameter while using an API instance
+
 ### Changed
 
 - Switched from Travis-CI to Github Actions
diff --git a/docs/migrate-to-psr18client.md b/docs/migrate-to-psr18client.md
index e3cc8fdd..35066a7d 100644
--- a/docs/migrate-to-psr18client.md
+++ b/docs/migrate-to-psr18client.md
@@ -1,6 +1,6 @@
 # Migrate from `Redmine\Client` to `Redmine\Client\Psr18Client`
 
-Since `php-redmine-api` v1.7.0 there is a new PSR-18 based client `Redmine\Client\Psr18Client`. This guide will help you to migrate your code if you want to use an app-wide PSR-18 HTTP client.
+Since `v1.7.0` there is a new PSR-18 based client `Redmine\Client\Psr18Client`. This guide will help you to migrate your code if you want to use an app-wide PSR-18 HTTP client.
 
 ## 1. Use new client methods
 
diff --git a/docs/usage.md b/docs/usage.md
index 149ff130..07110609 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -51,6 +51,8 @@ client.
 
 #### Native cURL Client `Redmine\Client\NativeCurlClient`
 
+> :bulb: The `Redmine\Client\NativeCurlClient` class was introduced in `v1.8.0`.
+
 Every client requires a URL to your Redmine instance and either a valid
 Apikey...
 
@@ -100,6 +102,8 @@ $client = new \Redmine\Client('https://redmine.example.com', '1234567890abcdfgh'
 
 #### Psr-18 compatible Client `Redmine\Client\Psr18Client`
 
+> :bulb: The `Redmine\Client\Psr18Client` class was introduced in `v1.7.0`.
+
 The `Psr18Client` requires
 
 - a `Psr\Http\Client\ClientInterface` implementation (like guzzlehttp/guzzle) ([possible implementations](https://packagist.org/providers/psr/http-client-implementation))
@@ -117,7 +121,7 @@ The `Psr18Client` requires
 require_once 'vendor/autoload.php';
 +
 +$guzzle = \GuzzleHttp\Client();
-+$psr17Factory = new \Nyholm\Psr7\Factory\Psr17Factory();
++$psr17Factory = new \GuzzleHttp\Psr7\HttpFactory();
 +
 +// Instantiate with ApiKey
 +$client = new Redmine\Client\Prs18Client($guzzle, $psr17Factory, $psr17Factory, 'https://redmine.example.com', '1234567890abcdfgh');
@@ -147,7 +151,7 @@ require_once 'vendor/autoload.php';
 +use Psr\Http\Message\ResponseInterface;
 +
 $guzzle = \GuzzleHttp\Client();
-$psr17Factory = new \Nyholm\Psr7\Factory\Psr17Factory();
+$psr17Factory = new \GuzzleHttp\Psr7\HttpFactory();
 
 +$guzzleWrapper = new class(\GuzzleHttp\Client $guzzle) implements ClientInterface
 +{
@@ -195,6 +199,22 @@ $client->startImpersonateUser('kim');
 $client->stopImpersonateUser();
 ```
 
+## Error handling
+
+Every exception implement the interface `Redmine\Exception` making it easy to catch Redmine specific issues.
+
+> :bulb: The `Redmine\Exception` interface was introduced in `v2.1.0`.
+
+```php
+try {
+    $client->getApi('issue')->create($data);
+} catch (\Redmine\Exception $e) {
+    // exceptions from kbsali/redmine-api
+} catch (\Throwable $e) {
+    // other errors
+}
+```
+
 ## API
 
 You can now use the `getApi()` method to create and get a specific Redmine API.
diff --git a/src/Redmine/Api/Group.php b/src/Redmine/Api/Group.php
index 65eef20b..3b364af9 100644
--- a/src/Redmine/Api/Group.php
+++ b/src/Redmine/Api/Group.php
@@ -2,6 +2,9 @@
 
 namespace Redmine\Api;
 
+use Exception;
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Handling of groups.
  *
@@ -56,7 +59,7 @@ public function listing($forceUpdate = false)
      *
      * @param array $params the new group data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return \SimpleXMLElement
      */
@@ -71,7 +74,7 @@ public function create(array $params = [])
         if (
             !isset($params['name'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `name`');
         }
 
         $xml = $this->buildXML($params);
@@ -86,11 +89,11 @@ public function create(array $params = [])
      *
      * @param int $id
      *
-     * @throws \Exception Not implemented
+     * @throws Exception Not implemented
      */
     public function update($id, array $params = [])
     {
-        throw new \Exception('Not implemented');
+        throw new Exception('Not implemented');
     }
 
     /**
diff --git a/src/Redmine/Api/IssueCategory.php b/src/Redmine/Api/IssueCategory.php
index 5e2cbba6..66eaed62 100644
--- a/src/Redmine/Api/IssueCategory.php
+++ b/src/Redmine/Api/IssueCategory.php
@@ -2,6 +2,8 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Listing issue categories, creating, editing.
  *
@@ -91,7 +93,7 @@ public function show($id)
      * @param string|int $project project id or literal identifier
      * @param array      $params  the new issue category data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -106,7 +108,7 @@ public function create($project, array $params = [])
         if (
             !isset($params['name'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `name`');
         }
 
         $xml = new \SimpleXMLElement('<?xml version="1.0"?><issue_category></issue_category>');
diff --git a/src/Redmine/Api/Membership.php b/src/Redmine/Api/Membership.php
index a552e3d3..99695f5f 100644
--- a/src/Redmine/Api/Membership.php
+++ b/src/Redmine/Api/Membership.php
@@ -2,6 +2,8 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Handling project memberships.
  *
@@ -38,7 +40,7 @@ public function all($project, array $params = [])
      * @param string|int $project project id or literal identifier
      * @param array      $params  the new membership data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -51,7 +53,7 @@ public function create($project, array $params = [])
         $params = $this->sanitizeParams($defaults, $params);
 
         if (!isset($params['user_id']) || !isset($params['role_ids'])) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `user_id`, `role_ids`');
         }
 
         $xml = $this->buildXML($params);
@@ -67,7 +69,7 @@ public function create($project, array $params = [])
      * @param int   $id     id of the membership
      * @param array $params the new membership data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -79,7 +81,7 @@ public function update($id, array $params = [])
         $params = $this->sanitizeParams($defaults, $params);
 
         if (!isset($params['role_ids'])) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Missing mandatory parameters');
         }
 
         $xml = $this->buildXML($params);
diff --git a/src/Redmine/Api/Project.php b/src/Redmine/Api/Project.php
index c7c97b75..d12f5d1a 100755
--- a/src/Redmine/Api/Project.php
+++ b/src/Redmine/Api/Project.php
@@ -2,6 +2,8 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Listing projects, creating, editing.
  *
@@ -98,7 +100,7 @@ public function show($id, array $params = [])
      *
      * @param array $params the new project data
      *
-     * @throws \Exception
+     * @throws MissingParameterException
      *
      * @return \SimpleXMLElement
      */
@@ -115,7 +117,7 @@ public function create(array $params = [])
             !isset($params['name'])
          || !isset($params['identifier'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `name`, `identifier`');
         }
 
         $xml = $this->prepareParamsXml($params);
diff --git a/src/Redmine/Api/TimeEntry.php b/src/Redmine/Api/TimeEntry.php
index 81966b22..e91491f0 100644
--- a/src/Redmine/Api/TimeEntry.php
+++ b/src/Redmine/Api/TimeEntry.php
@@ -2,6 +2,8 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Listing time entries, creating, editing.
  *
@@ -50,7 +52,7 @@ public function show($id)
      *
      * @param array $params the new time entry data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -70,7 +72,7 @@ public function create(array $params = [])
             (!isset($params['issue_id']) && !isset($params['project_id']))
          || !isset($params['hours'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `issue_id` or `project_id`, `hours`');
         }
 
         $xml = new \SimpleXMLElement('<?xml version="1.0"?><time_entry></time_entry>');
diff --git a/src/Redmine/Api/User.php b/src/Redmine/Api/User.php
index dde78bbf..d1f70b82 100644
--- a/src/Redmine/Api/User.php
+++ b/src/Redmine/Api/User.php
@@ -2,6 +2,8 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Listing users, creating, editing.
  *
@@ -129,7 +131,7 @@ public function show($id, array $params = [])
      *
      * @param array $params the new user data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -150,7 +152,7 @@ public function create(array $params = [])
          || !isset($params['firstname'])
          || !isset($params['mail'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `login`, `lastname`, `firstname`, `mail`');
         }
         $xml = new \SimpleXMLElement('<?xml version="1.0"?><user></user>');
         foreach ($params as $k => $v) {
diff --git a/src/Redmine/Api/Version.php b/src/Redmine/Api/Version.php
index 5685b680..121dad71 100644
--- a/src/Redmine/Api/Version.php
+++ b/src/Redmine/Api/Version.php
@@ -2,6 +2,9 @@
 
 namespace Redmine\Api;
 
+use Redmine\Exception\InvalidParameterException;
+use Redmine\Exception\MissingParameterException;
+
 /**
  * Listing versions, creating, editing.
  *
@@ -94,7 +97,7 @@ public function show($id)
      * @param string|int $project project id or literal identifier
      * @param array      $params  the new issue category data
      *
-     * @throws \Exception Missing mandatory parameters
+     * @throws MissingParameterException Missing mandatory parameters
      *
      * @return string|false
      */
@@ -112,7 +115,7 @@ public function create($project, array $params = [])
         if (
             !isset($params['name'])
         ) {
-            throw new \Exception('Missing mandatory parameters');
+            throw new MissingParameterException('Theses parameters are mandatory: `name`');
         }
         $this->validateStatus($params);
         $this->validateSharing($params);
@@ -171,7 +174,7 @@ private function validateStatus(array $params = [])
             'closed',
         ];
         if (isset($params['status']) && !in_array($params['status'], $arrStatus)) {
-            throw new \Exception('Possible values for status : '.implode(', ', $arrStatus));
+            throw new InvalidParameterException('Possible values for status : '.implode(', ', $arrStatus));
         }
     }
 
@@ -185,7 +188,7 @@ private function validateSharing(array $params = [])
             'system' => 'With all projects',
         ];
         if (isset($params['sharing']) && !isset($arrSharing[$params['sharing']])) {
-            throw new \Exception('Possible values for sharing : '.implode(', ', array_keys($arrSharing)));
+            throw new InvalidParameterException('Possible values for sharing : '.implode(', ', array_keys($arrSharing)));
         }
     }
 
diff --git a/src/Redmine/Client/Client.php b/src/Redmine/Client/Client.php
index e7daf2f2..610b5234 100644
--- a/src/Redmine/Client/Client.php
+++ b/src/Redmine/Client/Client.php
@@ -2,8 +2,8 @@
 
 namespace Redmine\Client;
 
-use InvalidArgumentException;
 use Redmine\Api;
+use Redmine\Exception\InvalidApiNameException;
 
 /**
  * client interface.
@@ -11,7 +11,7 @@
 interface Client
 {
     /**
-     * @throws InvalidArgumentException if $name is not a valid api name
+     * @throws InvalidApiNameException if $name is not a valid api name
      */
     public function getApi(string $name): Api;
 
diff --git a/src/Redmine/Client/ClientApiTrait.php b/src/Redmine/Client/ClientApiTrait.php
index 2c1af81b..b8b47bb4 100644
--- a/src/Redmine/Client/ClientApiTrait.php
+++ b/src/Redmine/Client/ClientApiTrait.php
@@ -2,8 +2,8 @@
 
 namespace Redmine\Client;
 
-use InvalidArgumentException;
 use Redmine\Api;
+use Redmine\Exception\InvalidApiNameException;
 
 /**
  * Provide API instantiation to clients.
@@ -38,12 +38,12 @@ trait ClientApiTrait
     ];
 
     /**
-     * @throws InvalidArgumentException if $name is not a valid api name
+     * @throws InvalidApiNameException if $name is not a valid api name
      */
     public function getApi(string $name): Api
     {
         if (!isset($this->apiClassnames[$name])) {
-            throw new InvalidArgumentException(sprintf('`%s` is not a valid api. Possible apis are `%s`', $name, implode('`, `', array_keys($this->apiClassnames))));
+            throw new InvalidApiNameException(sprintf('`%s` is not a valid api. Possible apis are `%s`', $name, implode('`, `', array_keys($this->apiClassnames))));
         }
         if (isset($this->apiInstances[$name])) {
             return $this->apiInstances[$name];
diff --git a/src/Redmine/Client/NativeCurlClient.php b/src/Redmine/Client/NativeCurlClient.php
index 0b074fd0..4553a788 100644
--- a/src/Redmine/Client/NativeCurlClient.php
+++ b/src/Redmine/Client/NativeCurlClient.php
@@ -4,8 +4,8 @@
 
 namespace Redmine\Client;
 
-use Exception;
 use Redmine\Api;
+use Redmine\Exception\ClientException;
 
 /**
  * Native cURL client.
@@ -210,7 +210,7 @@ private function unsetHttpHeader(string $name): void
     }
 
     /**
-     * @throws Exception If anything goes wrong on curl request
+     * @throws ClientException If anything goes wrong on curl request
      */
     private function request(string $method, string $path, string $body = ''): bool
     {
@@ -225,7 +225,7 @@ private function request(string $method, string $path, string $body = ''): bool
         $curlErrorNumber = curl_errno($curl);
 
         if (CURLE_OK !== $curlErrorNumber) {
-            $e = new Exception(curl_error($curl), $curlErrorNumber);
+            $e = new ClientException(curl_error($curl), $curlErrorNumber);
             curl_close($curl);
             throw $e;
         }
diff --git a/src/Redmine/Client/Psr18Client.php b/src/Redmine/Client/Psr18Client.php
index cefc3b28..b7c17509 100644
--- a/src/Redmine/Client/Psr18Client.php
+++ b/src/Redmine/Client/Psr18Client.php
@@ -4,13 +4,13 @@
 
 namespace Redmine\Client;
 
-use Exception;
 use Psr\Http\Client\ClientExceptionInterface;
 use Psr\Http\Client\ClientInterface;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestFactoryInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Message\StreamFactoryInterface;
+use Redmine\Exception\ClientException;
 
 /**
  * Psr18 client.
@@ -136,7 +136,7 @@ public function getLastResponseBody(): string
     /**
      * Create and run a request.
      *
-     * @throws Exception If anything goes wrong on the request
+     * @throws ClientException If anything goes wrong on the request
      *
      * @return bool true if status code of the response is not 4xx oder 5xx
      */
@@ -149,7 +149,7 @@ private function runRequest(string $method, string $path, string $body = ''): bo
         try {
             $this->lastResponse = $this->httpClient->sendRequest($request);
         } catch (ClientExceptionInterface $e) {
-            throw new Exception($e->getMessage(), $e->getCode(), $e);
+            throw new ClientException($e->getMessage(), $e->getCode(), $e);
         }
 
         return $this->lastResponse->getStatusCode() < 400;
diff --git a/src/Redmine/Exception.php b/src/Redmine/Exception.php
new file mode 100644
index 00000000..fdc82d4b
--- /dev/null
+++ b/src/Redmine/Exception.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Redmine;
+
+use Throwable;
+
+interface Exception extends Throwable
+{
+}
diff --git a/src/Redmine/Exception/ClientException.php b/src/Redmine/Exception/ClientException.php
new file mode 100644
index 00000000..bf05b8be
--- /dev/null
+++ b/src/Redmine/Exception/ClientException.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Redmine\Exception;
+
+use Exception;
+use Redmine\Exception as RedmineException;
+
+class ClientException extends Exception implements RedmineException
+{
+}
diff --git a/src/Redmine/Exception/InvalidApiNameException.php b/src/Redmine/Exception/InvalidApiNameException.php
new file mode 100644
index 00000000..4aab40ea
--- /dev/null
+++ b/src/Redmine/Exception/InvalidApiNameException.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Redmine\Exception;
+
+use InvalidArgumentException;
+use Redmine\Exception as RedmineException;
+
+class InvalidApiNameException extends InvalidArgumentException implements RedmineException
+{
+}
diff --git a/src/Redmine/Exception/InvalidParameterException.php b/src/Redmine/Exception/InvalidParameterException.php
new file mode 100644
index 00000000..08311a8c
--- /dev/null
+++ b/src/Redmine/Exception/InvalidParameterException.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Redmine\Exception;
+
+use InvalidArgumentException;
+use Redmine\Exception as RedmineException;
+
+class InvalidParameterException extends InvalidArgumentException implements RedmineException
+{
+}
diff --git a/src/Redmine/Exception/MissingParameterException.php b/src/Redmine/Exception/MissingParameterException.php
new file mode 100644
index 00000000..222e1463
--- /dev/null
+++ b/src/Redmine/Exception/MissingParameterException.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Redmine\Exception;
+
+use InvalidArgumentException;
+use Redmine\Exception as RedmineException;
+
+class MissingParameterException extends InvalidArgumentException implements RedmineException
+{
+}
diff --git a/tests/Integration/GroupXmlTest.php b/tests/Integration/GroupXmlTest.php
index 575e61d1..7070050a 100644
--- a/tests/Integration/GroupXmlTest.php
+++ b/tests/Integration/GroupXmlTest.php
@@ -5,6 +5,7 @@
 use DOMDocument;
 use Exception;
 use PHPUnit\Framework\TestCase;
+use Redmine\Exception\MissingParameterException;
 use Redmine\Tests\Fixtures\MockClient;
 use SimpleXMLElement;
 
@@ -25,8 +26,8 @@ public function testCreateBlank()
         $api = $this->client->getApi('group');
         $this->assertInstanceOf('Redmine\Api\Group', $api);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         $api->create();
     }
diff --git a/tests/Integration/IssueCategoryXmlTest.php b/tests/Integration/IssueCategoryXmlTest.php
index ae9c88fe..d7207be7 100644
--- a/tests/Integration/IssueCategoryXmlTest.php
+++ b/tests/Integration/IssueCategoryXmlTest.php
@@ -5,6 +5,7 @@
 use DOMDocument;
 use Exception;
 use PHPUnit\Framework\TestCase;
+use Redmine\Exception\MissingParameterException;
 use Redmine\Tests\Fixtures\MockClient;
 use SimpleXMLElement;
 
@@ -25,8 +26,8 @@ public function testCreateBlank()
         $api = $this->client->getApi('issue_category');
         $this->assertInstanceOf('Redmine\Api\IssueCategory', $api);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         $api->create('aProject');
     }
diff --git a/tests/Integration/MembershipXmlTest.php b/tests/Integration/MembershipXmlTest.php
index 3cce1dc6..0dcd5614 100644
--- a/tests/Integration/MembershipXmlTest.php
+++ b/tests/Integration/MembershipXmlTest.php
@@ -5,6 +5,7 @@
 use DOMDocument;
 use Exception;
 use PHPUnit\Framework\TestCase;
+use Redmine\Exception\MissingParameterException;
 use Redmine\Tests\Fixtures\MockClient;
 use SimpleXMLElement;
 
@@ -25,8 +26,8 @@ public function testCreateBlank()
         $api = $this->client->getApi('membership');
         $this->assertInstanceOf('Redmine\Api\Membership', $api);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `user_id`, `role_ids`');
 
         $api->create('aProject');
     }
diff --git a/tests/Integration/ProjectXmlTest.php b/tests/Integration/ProjectXmlTest.php
index 83624905..88afd570 100644
--- a/tests/Integration/ProjectXmlTest.php
+++ b/tests/Integration/ProjectXmlTest.php
@@ -5,6 +5,7 @@
 use DOMDocument;
 use Exception;
 use PHPUnit\Framework\TestCase;
+use Redmine\Exception\MissingParameterException;
 use Redmine\Tests\Fixtures\MockClient;
 use SimpleXMLElement;
 
@@ -25,8 +26,8 @@ public function testCreateBlank()
         $api = $this->client->getApi('project');
         $this->assertInstanceOf('Redmine\Api\Project', $api);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`, `identifier`');
 
         $api->create();
     }
diff --git a/tests/Integration/UserXmlTest.php b/tests/Integration/UserXmlTest.php
index 90c42a3f..ea858bb7 100644
--- a/tests/Integration/UserXmlTest.php
+++ b/tests/Integration/UserXmlTest.php
@@ -5,6 +5,7 @@
 use DOMDocument;
 use Exception;
 use PHPUnit\Framework\TestCase;
+use Redmine\Exception\MissingParameterException;
 use Redmine\Tests\Fixtures\MockClient;
 use SimpleXMLElement;
 
@@ -25,8 +26,8 @@ public function testCreateBlank()
         $api = $this->client->getApi('user');
         $this->assertInstanceOf('Redmine\Api\User', $api);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `login`, `lastname`, `firstname`, `mail`');
 
         $api->create();
     }
diff --git a/tests/Unit/Api/GroupTest.php b/tests/Unit/Api/GroupTest.php
index 294db809..dd3e2e6b 100644
--- a/tests/Unit/Api/GroupTest.php
+++ b/tests/Unit/Api/GroupTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\Group;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\Group
@@ -341,7 +342,7 @@ public function testCreateCallsPost()
      *
      * @test
      */
-    public function testCreateThrowsExceptionIsNameIsMissing()
+    public function testCreateThrowsExceptionIfNameIsMissing()
     {
         // Test values
         $postParameter = [];
@@ -352,8 +353,8 @@ public function testCreateThrowsExceptionIsNameIsMissing()
         // Create the object under test
         $api = new Group($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         // Perform the tests
         $api->create($postParameter);
diff --git a/tests/Unit/Api/IssueCategoryTest.php b/tests/Unit/Api/IssueCategoryTest.php
index 83bb3427..c7b6ff8c 100644
--- a/tests/Unit/Api/IssueCategoryTest.php
+++ b/tests/Unit/Api/IssueCategoryTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\IssueCategory;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\IssueCategory
@@ -353,8 +354,8 @@ public function testCreateThrowsExceptionIfNameIsMissing()
         // Create the object under test
         $api = new IssueCategory($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         // Perform the tests
         $api->create(5, $parameters);
diff --git a/tests/Unit/Api/MembershipTest.php b/tests/Unit/Api/MembershipTest.php
index 757a8a36..9fb952c1 100644
--- a/tests/Unit/Api/MembershipTest.php
+++ b/tests/Unit/Api/MembershipTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\Membership;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\Membership
@@ -133,8 +134,8 @@ public function testCreateThrowsExceptionWithEmptyParameters()
         // Create the object under test
         $api = new Membership($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `user_id`, `role_ids`');
 
         // Perform the tests
         $this->assertSame($response, $api->create(5));
@@ -158,8 +159,8 @@ public function testCreateThrowsExceptionIfRoleIdsAreMissingInParameters()
         // Create the object under test
         $api = new Membership($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `user_id`, `role_ids`');
 
         // Perform the tests
         $this->assertSame($response, $api->create(5, ['user_id' => 4]));
diff --git a/tests/Unit/Api/ProjectTest.php b/tests/Unit/Api/ProjectTest.php
index 2e96f70f..27f757da 100644
--- a/tests/Unit/Api/ProjectTest.php
+++ b/tests/Unit/Api/ProjectTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\Project;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\Project
@@ -337,8 +338,8 @@ public function testCreateThrowsExceptionWithEmptyParameters()
         // Create the object under test
         $api = new Project($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`, `identifier`');
 
         // Perform the tests
         $this->assertSame($response, $api->create(['id' => 5]));
@@ -365,8 +366,8 @@ public function testCreateThrowsExceptionIfIdentifierIsMissingInParameters()
         // Create the object under test
         $api = new Project($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`, `identifier`');
 
         // Perform the tests
         $this->assertSame($response, $api->create($parameters));
@@ -393,8 +394,8 @@ public function testCreateThrowsExceptionIfNameIsMissingInParameters()
         // Create the object under test
         $api = new Project($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`, `identifier`');
 
         // Perform the tests
         $this->assertSame($response, $api->create($parameters));
diff --git a/tests/Unit/Api/TimeEntryTest.php b/tests/Unit/Api/TimeEntryTest.php
index 90694674..efb9e92e 100644
--- a/tests/Unit/Api/TimeEntryTest.php
+++ b/tests/Unit/Api/TimeEntryTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\TimeEntry;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\TimeEntry
@@ -158,8 +159,8 @@ public function testCreateThrowsExceptionWithEmptyParameters()
         // Create the object under test
         $api = new TimeEntry($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `issue_id` or `project_id`, `hours`');
 
         // Perform the tests
         $this->assertSame($response, $api->create(['id' => 5]));
@@ -186,8 +187,8 @@ public function testCreateThrowsExceptionIfIssueIdAndProjectIdAreMissingInParame
         // Create the object under test
         $api = new TimeEntry($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `issue_id` or `project_id`, `hours`');
 
         // Perform the tests
         $this->assertSame($response, $api->create($parameters));
@@ -215,8 +216,8 @@ public function testCreateThrowsExceptionIfHoursAreMissingInParameters()
         // Create the object under test
         $api = new TimeEntry($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `issue_id` or `project_id`, `hours`');
 
         // Perform the tests
         $this->assertSame($response, $api->create($parameters));
diff --git a/tests/Unit/Api/UserTest.php b/tests/Unit/Api/UserTest.php
index 095b44d1..b1b7c96a 100644
--- a/tests/Unit/Api/UserTest.php
+++ b/tests/Unit/Api/UserTest.php
@@ -6,6 +6,7 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\User;
 use Redmine\Client\Client;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\User
@@ -263,8 +264,8 @@ public function testCreateThrowsExceptionWithEmptyParameters()
         // Create the object under test
         $api = new User($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `login`, `lastname`, `firstname`, `mail`');
 
         // Perform the tests
         $this->assertSame($response, $api->create());
@@ -288,8 +289,8 @@ public function testCreateThrowsExceptionIfValueIsMissingInParameters($parameter
         // Create the object under test
         $api = new User($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `login`, `lastname`, `firstname`, `mail`');
 
         // Perform the tests
         $api->create($parameters);
diff --git a/tests/Unit/Api/VersionTest.php b/tests/Unit/Api/VersionTest.php
index 230744ec..dfe9c1ed 100644
--- a/tests/Unit/Api/VersionTest.php
+++ b/tests/Unit/Api/VersionTest.php
@@ -6,6 +6,8 @@
 use PHPUnit\Framework\TestCase;
 use Redmine\Api\Version;
 use Redmine\Client\Client;
+use Redmine\Exception\InvalidParameterException;
+use Redmine\Exception\MissingParameterException;
 
 /**
  * @coversDefaultClass \Redmine\Api\Version
@@ -211,8 +213,8 @@ public function testCreateThrowsExceptionWithEmptyParameters()
         // Create the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         // Perform the tests
         $api->create(5);
@@ -238,8 +240,8 @@ public function testCreateThrowsExceptionWithMissingNameInParameters()
         // Create the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         // Perform the tests
         $api->create(5, $parameters);
@@ -267,8 +269,8 @@ public function testCreateThrowsExceptionWithInvalidStatus()
         // Create the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
-        $this->expectExceptionMessage('Missing mandatory parameters');
+        $this->expectException(MissingParameterException::class);
+        $this->expectExceptionMessage('Theses parameters are mandatory: `name`');
 
         // Perform the tests
         $api->create('test', $parameters);
@@ -377,7 +379,7 @@ public function testUpdateThrowsExceptionWithInvalidStatus()
         // Create the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
+        $this->expectException(InvalidParameterException::class);
         $this->expectExceptionMessage('Possible values for status : open, locked, closed');
 
         // Perform the tests
@@ -757,7 +759,7 @@ public function testCreateThrowsExceptionWithInvalidSharing($sharingValue)
         // Create the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
+        $this->expectException(InvalidParameterException::class);
         $this->expectExceptionMessage('Possible values for sharing : none, descendants, hierarchy, tree, system');
 
         // Perform the tests
@@ -880,7 +882,7 @@ public function testUpdateThrowsExceptionWithInvalidSharing($sharingValue)
         // Update the object under test
         $api = new Version($client);
 
-        $this->expectException(Exception::class);
+        $this->expectException(InvalidParameterException::class);
         $this->expectExceptionMessage('Possible values for sharing : none, descendants, hierarchy, tree, system');
 
         // Perform the tests
diff --git a/tests/Unit/Exception/ClientExceptionTest.php b/tests/Unit/Exception/ClientExceptionTest.php
new file mode 100644
index 00000000..c0195534
--- /dev/null
+++ b/tests/Unit/Exception/ClientExceptionTest.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Redmine\Tests\Unit\Exception;
+
+use Exception;
+use PHPUnit\Framework\TestCase;
+use Redmine\Exception as RedmineException;
+use Redmine\Exception\ClientException;
+
+class ClientExceptionTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function testClientException()
+    {
+        $exception = new ClientException();
+
+        $this->assertInstanceOf(Exception::class, $exception);
+        $this->assertInstanceOf(RedmineException::class, $exception);
+    }
+}
diff --git a/tests/Unit/Exception/InvalidApiNameExceptionTest.php b/tests/Unit/Exception/InvalidApiNameExceptionTest.php
new file mode 100644
index 00000000..838aade8
--- /dev/null
+++ b/tests/Unit/Exception/InvalidApiNameExceptionTest.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Redmine\Tests\Unit\Exception;
+
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+use Redmine\Exception as RedmineException;
+use Redmine\Exception\InvalidApiNameException;
+
+class InvalidApiNameExceptionTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function testInvalidApiNameException()
+    {
+        $exception = new InvalidApiNameException();
+
+        $this->assertInstanceOf(InvalidArgumentException::class, $exception);
+        $this->assertInstanceOf(RedmineException::class, $exception);
+    }
+}
diff --git a/tests/Unit/Exception/InvalidParameterExceptionTest.php b/tests/Unit/Exception/InvalidParameterExceptionTest.php
new file mode 100644
index 00000000..0324d9f4
--- /dev/null
+++ b/tests/Unit/Exception/InvalidParameterExceptionTest.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Redmine\Tests\Unit\Exception;
+
+use Exception;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+use Redmine\Exception as RedmineException;
+use Redmine\Exception\InvalidParameterException;
+
+class InvalidParameterExceptionTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function testInvalidParameterException()
+    {
+        $exception = new InvalidParameterException();
+
+        $this->assertInstanceOf(Exception::class, $exception);
+        $this->assertInstanceOf(InvalidArgumentException::class, $exception);
+        $this->assertInstanceOf(RedmineException::class, $exception);
+    }
+}
diff --git a/tests/Unit/Exception/MissingParameterExceptionTest.php b/tests/Unit/Exception/MissingParameterExceptionTest.php
new file mode 100644
index 00000000..31b00c0e
--- /dev/null
+++ b/tests/Unit/Exception/MissingParameterExceptionTest.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Redmine\Tests\Unit\Exception;
+
+use Exception;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+use Redmine\Exception as RedmineException;
+use Redmine\Exception\MissingParameterException;
+
+class MissingParameterExceptionTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function testMissingParameterException()
+    {
+        $exception = new MissingParameterException();
+
+        $this->assertInstanceOf(Exception::class, $exception);
+        $this->assertInstanceOf(InvalidArgumentException::class, $exception);
+        $this->assertInstanceOf(RedmineException::class, $exception);
+    }
+}