diff --git a/composer.json b/composer.json
index 1122551..28ef787 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
     },
     "autoload": {
         "psr-4": {
-            "WBW\\Library\\SMSMode\\": ""
+            "WBW\\Library\\SMSMode\\": "src/"
         },
         "exclude-from-classmap": [
             "/Tests/"
@@ -32,7 +32,7 @@
     },
     "autoload-dev": {
         "psr-4": {
-            "WBW\\Library\\SMSMode\\Tests\\": "Tests/"
+            "WBW\\Library\\SMSMode\\Tests\\": "tests/"
         }
     },
     "config": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index f4a8aa3..c1da8ae 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -4,7 +4,7 @@
          xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/5.7/phpunit.xsd"
          backupGlobals="false"
          backupStaticAttributes="false"
-         bootstrap="Tests/bootstrap.php"
+         bootstrap="tests/bootstrap.php"
          colors="true"
          convertErrorsToExceptions="true"
          convertNoticesToExceptions="true"
@@ -14,17 +14,16 @@
          syntaxCheck="false">
     <filter>
         <whitelist>
-            <directory>./</directory>
+            <directory>./src</directory>
             <exclude>
                 <directory>Resources</directory>
-                <directory>Tests</directory>
                 <directory>vendor</directory>
             </exclude>
         </whitelist>
     </filter>
     <testsuites>
         <testsuite name="webeweb/smsmode-library">
-            <directory>./Tests</directory>
+            <directory>./tests</directory>
         </testsuite>
     </testsuites>
 </phpunit>
diff --git a/API/SMSModeMessageInterface.php b/src/API/SMSModeMessageInterface.php
similarity index 100%
rename from API/SMSModeMessageInterface.php
rename to src/API/SMSModeMessageInterface.php
diff --git a/API/SMSModeRequestInterface.php b/src/API/SMSModeRequestInterface.php
similarity index 100%
rename from API/SMSModeRequestInterface.php
rename to src/API/SMSModeRequestInterface.php
diff --git a/API/SMSModeResponseInterface.php b/src/API/SMSModeResponseInterface.php
similarity index 100%
rename from API/SMSModeResponseInterface.php
rename to src/API/SMSModeResponseInterface.php
diff --git a/Authentication/SMSModeAuthentication.php b/src/Authentication/SMSModeAuthentication.php
similarity index 100%
rename from Authentication/SMSModeAuthentication.php
rename to src/Authentication/SMSModeAuthentication.php
diff --git a/Exception/AbstractSMSModeException.php b/src/Exception/AbstractSMSModeException.php
similarity index 100%
rename from Exception/AbstractSMSModeException.php
rename to src/Exception/AbstractSMSModeException.php
diff --git a/Exception/SMSModeInvalidNumberException.php b/src/Exception/SMSModeInvalidNumberException.php
similarity index 100%
rename from Exception/SMSModeInvalidNumberException.php
rename to src/Exception/SMSModeInvalidNumberException.php
diff --git a/Exception/SMSModeMaxLimitNumberReachedException.php b/src/Exception/SMSModeMaxLimitNumberReachedException.php
similarity index 100%
rename from Exception/SMSModeMaxLimitNumberReachedException.php
rename to src/Exception/SMSModeMaxLimitNumberReachedException.php
diff --git a/Exception/SMSModeMessageTooLongException.php b/src/Exception/SMSModeMessageTooLongException.php
similarity index 100%
rename from Exception/SMSModeMessageTooLongException.php
rename to src/Exception/SMSModeMessageTooLongException.php
diff --git a/Helper/NumberHelper.php b/src/Helper/NumberHelper.php
similarity index 100%
rename from Helper/NumberHelper.php
rename to src/Helper/NumberHelper.php
diff --git a/Provider/SMSModeProvider.php b/src/Provider/SMSModeProvider.php
similarity index 100%
rename from Provider/SMSModeProvider.php
rename to src/Provider/SMSModeProvider.php
diff --git a/Request/SMSModeAccountBalanceRequest.php b/src/Request/SMSModeAccountBalanceRequest.php
similarity index 100%
rename from Request/SMSModeAccountBalanceRequest.php
rename to src/Request/SMSModeAccountBalanceRequest.php
diff --git a/Request/SMSModeCreateSubaccountRequest.php b/src/Request/SMSModeCreateSubaccountRequest.php
similarity index 100%
rename from Request/SMSModeCreateSubaccountRequest.php
rename to src/Request/SMSModeCreateSubaccountRequest.php
diff --git a/Request/SMSModeCreditTransferRequest.php b/src/Request/SMSModeCreditTransferRequest.php
similarity index 100%
rename from Request/SMSModeCreditTransferRequest.php
rename to src/Request/SMSModeCreditTransferRequest.php
diff --git a/Request/SMSModeDeleteSubaccountRequest.php b/src/Request/SMSModeDeleteSubaccountRequest.php
similarity index 100%
rename from Request/SMSModeDeleteSubaccountRequest.php
rename to src/Request/SMSModeDeleteSubaccountRequest.php
diff --git a/Request/SMSModeGetResponsesRequest.php b/src/Request/SMSModeGetResponsesRequest.php
similarity index 100%
rename from Request/SMSModeGetResponsesRequest.php
rename to src/Request/SMSModeGetResponsesRequest.php
diff --git a/Request/SMSModeReceptionReportRequest.php b/src/Request/SMSModeReceptionReportRequest.php
similarity index 100%
rename from Request/SMSModeReceptionReportRequest.php
rename to src/Request/SMSModeReceptionReportRequest.php
diff --git a/Request/SMSModeSendSMSRequest.php b/src/Request/SMSModeSendSMSRequest.php
similarity index 100%
rename from Request/SMSModeSendSMSRequest.php
rename to src/Request/SMSModeSendSMSRequest.php
diff --git a/Resources/doc/API_HTTP_2.7.pdf b/src/Resources/doc/API_HTTP_2.7.pdf
similarity index 100%
rename from Resources/doc/API_HTTP_2.7.pdf
rename to src/Resources/doc/API_HTTP_2.7.pdf
diff --git a/Resources/doc/API_HTTP_3.1.pdf b/src/Resources/doc/API_HTTP_3.1.pdf
similarity index 100%
rename from Resources/doc/API_HTTP_3.1.pdf
rename to src/Resources/doc/API_HTTP_3.1.pdf
diff --git a/Response/AbstractSMSModeResponse.php b/src/Response/AbstractSMSModeResponse.php
similarity index 100%
rename from Response/AbstractSMSModeResponse.php
rename to src/Response/AbstractSMSModeResponse.php
diff --git a/Response/SMSModeAccountBalanceResponse.php b/src/Response/SMSModeAccountBalanceResponse.php
similarity index 100%
rename from Response/SMSModeAccountBalanceResponse.php
rename to src/Response/SMSModeAccountBalanceResponse.php
diff --git a/Response/SMSModeCreateSubaccountResponse.php b/src/Response/SMSModeCreateSubaccountResponse.php
similarity index 100%
rename from Response/SMSModeCreateSubaccountResponse.php
rename to src/Response/SMSModeCreateSubaccountResponse.php
diff --git a/Response/SMSModeCreditTransferResponse.php b/src/Response/SMSModeCreditTransferResponse.php
similarity index 100%
rename from Response/SMSModeCreditTransferResponse.php
rename to src/Response/SMSModeCreditTransferResponse.php
diff --git a/Response/SMSModeDeleteSubaccountResponse.php b/src/Response/SMSModeDeleteSubaccountResponse.php
similarity index 100%
rename from Response/SMSModeDeleteSubaccountResponse.php
rename to src/Response/SMSModeDeleteSubaccountResponse.php
diff --git a/Response/SMSModeGetResponsesResponse.php b/src/Response/SMSModeGetResponsesResponse.php
similarity index 100%
rename from Response/SMSModeGetResponsesResponse.php
rename to src/Response/SMSModeGetResponsesResponse.php
diff --git a/Response/SMSModeReceptionReportResponse.php b/src/Response/SMSModeReceptionReportResponse.php
similarity index 100%
rename from Response/SMSModeReceptionReportResponse.php
rename to src/Response/SMSModeReceptionReportResponse.php
diff --git a/Response/SMSModeSendSMSResponse.php b/src/Response/SMSModeSendSMSResponse.php
similarity index 100%
rename from Response/SMSModeSendSMSResponse.php
rename to src/Response/SMSModeSendSMSResponse.php
diff --git a/Utility/NumberUtility.php b/src/Utility/NumberUtility.php
similarity index 100%
rename from Utility/NumberUtility.php
rename to src/Utility/NumberUtility.php
diff --git a/Tests/Authentication/SMSModeAuthenticationTest.php b/tests/Authentication/SMSModeAuthenticationTest.php
similarity index 100%
rename from Tests/Authentication/SMSModeAuthenticationTest.php
rename to tests/Authentication/SMSModeAuthenticationTest.php
diff --git a/Tests/Exception/SMSModeInvalidNumberExceptionTest.php b/tests/Exception/SMSModeInvalidNumberExceptionTest.php
similarity index 100%
rename from Tests/Exception/SMSModeInvalidNumberExceptionTest.php
rename to tests/Exception/SMSModeInvalidNumberExceptionTest.php
diff --git a/Tests/Exception/SMSModeMaxLimitNumberReachedExceptionTest.php b/tests/Exception/SMSModeMaxLimitNumberReachedExceptionTest.php
similarity index 100%
rename from Tests/Exception/SMSModeMaxLimitNumberReachedExceptionTest.php
rename to tests/Exception/SMSModeMaxLimitNumberReachedExceptionTest.php
diff --git a/Tests/Exception/SMSModeMessageTooLongExceptionTest.php b/tests/Exception/SMSModeMessageTooLongExceptionTest.php
similarity index 100%
rename from Tests/Exception/SMSModeMessageTooLongExceptionTest.php
rename to tests/Exception/SMSModeMessageTooLongExceptionTest.php
diff --git a/Tests/Helper/NumberHelperTest.php b/tests/Helper/NumberHelperTest.php
similarity index 100%
rename from Tests/Helper/NumberHelperTest.php
rename to tests/Helper/NumberHelperTest.php
diff --git a/Tests/Provider/SMSModeProviderTest.php b/tests/Provider/SMSModeProviderTest.php
similarity index 100%
rename from Tests/Provider/SMSModeProviderTest.php
rename to tests/Provider/SMSModeProviderTest.php
diff --git a/Tests/Request/SMSModeAccountBalanceRequestTest.php b/tests/Request/SMSModeAccountBalanceRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeAccountBalanceRequestTest.php
rename to tests/Request/SMSModeAccountBalanceRequestTest.php
diff --git a/Tests/Request/SMSModeCreateSubaccountRequestTest.php b/tests/Request/SMSModeCreateSubaccountRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeCreateSubaccountRequestTest.php
rename to tests/Request/SMSModeCreateSubaccountRequestTest.php
diff --git a/Tests/Request/SMSModeCreditTransferRequestTest.php b/tests/Request/SMSModeCreditTransferRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeCreditTransferRequestTest.php
rename to tests/Request/SMSModeCreditTransferRequestTest.php
diff --git a/Tests/Request/SMSModeDeleteSubaccountRequestTest.php b/tests/Request/SMSModeDeleteSubaccountRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeDeleteSubaccountRequestTest.php
rename to tests/Request/SMSModeDeleteSubaccountRequestTest.php
diff --git a/Tests/Request/SMSModeGetResponsesRequestTest.php b/tests/Request/SMSModeGetResponsesRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeGetResponsesRequestTest.php
rename to tests/Request/SMSModeGetResponsesRequestTest.php
diff --git a/Tests/Request/SMSModeReceptionReportRequestTest.php b/tests/Request/SMSModeReceptionReportRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeReceptionReportRequestTest.php
rename to tests/Request/SMSModeReceptionReportRequestTest.php
diff --git a/Tests/Request/SMSModeSendSMSRequestTest.php b/tests/Request/SMSModeSendSMSRequestTest.php
similarity index 100%
rename from Tests/Request/SMSModeSendSMSRequestTest.php
rename to tests/Request/SMSModeSendSMSRequestTest.php
diff --git a/Tests/Response/SMSModeAccountBalanceResponseTest.php b/tests/Response/SMSModeAccountBalanceResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeAccountBalanceResponseTest.php
rename to tests/Response/SMSModeAccountBalanceResponseTest.php
diff --git a/Tests/Response/SMSModeCreateSubaccountResponseTest.php b/tests/Response/SMSModeCreateSubaccountResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeCreateSubaccountResponseTest.php
rename to tests/Response/SMSModeCreateSubaccountResponseTest.php
diff --git a/Tests/Response/SMSModeCreditTransferResponseTest.php b/tests/Response/SMSModeCreditTransferResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeCreditTransferResponseTest.php
rename to tests/Response/SMSModeCreditTransferResponseTest.php
diff --git a/Tests/Response/SMSModeDeleteSubaccountResponseTest.php b/tests/Response/SMSModeDeleteSubaccountResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeDeleteSubaccountResponseTest.php
rename to tests/Response/SMSModeDeleteSubaccountResponseTest.php
diff --git a/Tests/Response/SMSModeGetResponsesResponseTest.php b/tests/Response/SMSModeGetResponsesResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeGetResponsesResponseTest.php
rename to tests/Response/SMSModeGetResponsesResponseTest.php
diff --git a/Tests/Response/SMSModeReceptionReportResponseTest.php b/tests/Response/SMSModeReceptionReportResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeReceptionReportResponseTest.php
rename to tests/Response/SMSModeReceptionReportResponseTest.php
diff --git a/Tests/Response/SMSModeSendSMSResponseTest.php b/tests/Response/SMSModeSendSMSResponseTest.php
similarity index 100%
rename from Tests/Response/SMSModeSendSMSResponseTest.php
rename to tests/Response/SMSModeSendSMSResponseTest.php
diff --git a/Tests/Utility/NumberUtilityTest.php b/tests/Utility/NumberUtilityTest.php
similarity index 100%
rename from Tests/Utility/NumberUtilityTest.php
rename to tests/Utility/NumberUtilityTest.php
diff --git a/Tests/autoload.php.dist b/tests/autoload.php.dist
similarity index 100%
rename from Tests/autoload.php.dist
rename to tests/autoload.php.dist
diff --git a/Tests/bootstrap.php b/tests/bootstrap.php
similarity index 100%
rename from Tests/bootstrap.php
rename to tests/bootstrap.php