diff --git a/composer.json b/composer.json
index 1ad61bf..be68fa4 100644
--- a/composer.json
+++ b/composer.json
@@ -6,6 +6,11 @@
       "ByJG\\MicroOrm\\": "src/"
     }
   },
+  "autoload-dev": {
+    "psr-4": {
+      "Test\\": "tests/"
+    }
+  },
   "prefer-stable": true,
   "minimum-stability": "dev",
   "require": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index d5df793..13600e9 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -4,33 +4,33 @@ To change this license header, choose License Headers in Project Properties.
 To change this template file, choose Tools | Templates
 and open the template in the editor.
 -->
-
 <!-- see http://www.phpunit.de/wiki/Documentation -->
-<phpunit bootstrap="./vendor/autoload.php"
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         bootstrap="./vendor/autoload.php"
          colors="true"
          testdox="true"
          convertErrorsToExceptions="true"
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          convertDeprecationsToExceptions="true"
-         stopOnFailure="false">
-
-    <php>
-        <ini name="display_errors" value="On" />
-        <ini name="display_startup_errors" value="On" />
-        <ini name="error_reporting" value="E_ALL" />
-    </php>
+         stopOnFailure="false"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
 
-    <filter>
-        <whitelist>
-            <directory>./src</directory>
-        </whitelist>
-    </filter>
+  <php>
+    <ini name="display_errors" value="On"/>
+    <ini name="display_startup_errors" value="On"/>
+    <ini name="error_reporting" value="E_ALL"/>
+  </php>
 
-    <testsuites>
-        <testsuite name="Test Suite">
-            <directory>./tests/</directory>
-        </testsuite>
-    </testsuites>
+  <coverage>
+    <include>
+      <directory>./src</directory>
+    </include>
+  </coverage>
 
+  <testsuites>
+    <testsuite name="Test Suite">
+      <directory>./tests/</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>
diff --git a/src/Mapper.php b/src/Mapper.php
index 0099cf7..6826779 100644
--- a/src/Mapper.php
+++ b/src/Mapper.php
@@ -143,9 +143,39 @@ public function getEntity(array $fieldValues = [])
         }
 
         return $instance;
+    }
+
+    public function getQuery(): Query
+    {
+        return Query::getInstance()
+            ->table($this->table);
+    }
 
+    public function getQueryBasic(): QueryBasic
+    {
+        return QueryBasic::getInstance()
+            ->table($this->table);
+    }
+
+    public function getDeleteQuery(): DeleteQuery
+    {
+        return DeleteQuery::getInstance()
+            ->table($this->table);
     }
 
+    public function getInsertQuery(): InsertQuery
+    {
+        return InsertQuery::getInstance()
+            ->table($this->table);
+    }
+
+    public function getUpdateQuery(): UpdateQuery
+    {
+        return UpdateQuery::getInstance()
+            ->table($this->table);
+    }
+
+
     /**
      * @return string
      */
diff --git a/src/ORMSubject.php b/src/ORMSubject.php
index 8057cc9..960f265 100644
--- a/src/ORMSubject.php
+++ b/src/ORMSubject.php
@@ -2,6 +2,8 @@
 
 namespace ByJG\MicroOrm;
 
+use ByJG\MicroOrm\Exception\InvalidArgumentException;
+
 class ORMSubject
 {
     const EVENT_INSERT = 'insert';
@@ -34,6 +36,11 @@ public function addObserver(ObserverProcessorInterface $observerProcessor, Repos
         if (!isset($this->observers[$observerProcessor->getObserverdTable()])) {
             $this->observers[$observerProcessor->getObserverdTable()] = [];
         }
+        foreach ($this->observers[$observerProcessor->getObserverdTable()] as $observer) {
+            if (get_class($observer->getObserverdProcessor()) === get_class($observerProcessor) && get_class($observer->getRepository()) === get_class($observer_in)) {
+                throw new InvalidArgumentException("Observer already exists");
+            }
+        }
         $this->observers[$observerProcessor->getObserverdTable()][] = new ObserverProcessorInternal($observerProcessor, $observer_in);
     }
 
diff --git a/src/Repository.php b/src/Repository.php
index ec0e942..771dc5b 100644
--- a/src/Repository.php
+++ b/src/Repository.php
@@ -133,23 +133,24 @@ public function get($pkId)
     }
 
     /**
-     * @param array $pkId
-     * @return mixed|null
-     * @throws \ByJG\MicroOrm\Exception\InvalidArgumentException
+     * @param array|int $pkId
+     * @return bool
+     * @throws RepositoryReadOnlyException
+     * @throws Exception\InvalidArgumentException
      */
     public function delete($pkId)
     {
         [$filterList, $filterKeys] = $this->getPkFilter($pkId);
-        $updatable = DeleteQuery::getInstance()
-            ->table($this->mapper->getTable())
+        $updatable = $this->getMapper()->getDeleteQuery()
             ->where($filterList, $filterKeys);
 
         return $this->deleteByQuery($updatable);
     }
 
     /**
-     * @param UpdateBuilderInterface $updatable
+     * @param DeleteQuery $updatable
      * @return bool
+     * @throws Exception\InvalidArgumentException
      * @throws RepositoryReadOnlyException
      */
     public function deleteByQuery(DeleteQuery $updatable)
@@ -174,8 +175,7 @@ public function deleteByQuery(DeleteQuery $updatable)
      */
     public function getByFilter($filter, array $params, $forUpdate = false)
     {
-        $query = new Query();
-        $query->table($this->mapper->getTable())
+        $query = $this->getMapper()->getQuery()
             ->where($filter, $params);
 
         if ($forUpdate) {
@@ -315,14 +315,12 @@ public function save($instance, UpdateConstraint $updateConstraint = null)
         if ($isInsert) {
             $closure = $this->beforeInsert;
             $array = $closure($array);
-            $updatable = InsertQuery::getInstance()
-                ->table($this->mapper->getTable())
+            $updatable = $this->getMapper()->getInsertQuery()
                 ->fields(array_keys($array));
         } else {
             $closure = $this->beforeUpdate;
             $array = $closure($array);
-            $updatable = UpdateQuery::getInstance()
-                ->table($this->mapper->getTable());
+            $updatable = $this->getMapper()->getUpdateQuery();
             foreach ($array as $field => $value) {
                 $updatable->set($field, $value);
             }
diff --git a/tests/RepositoryTest.php b/tests/RepositoryTest.php
index 446023e..2af7e49 100644
--- a/tests/RepositoryTest.php
+++ b/tests/RepositoryTest.php
@@ -6,6 +6,7 @@
 use ByJG\AnyDataset\Db\Factory;
 use ByJG\MicroOrm\DeleteQuery;
 use ByJG\MicroOrm\Exception\AllowOnlyNewValuesConstraintException;
+use ByJG\MicroOrm\Exception\InvalidArgumentException;
 use ByJG\MicroOrm\Exception\RepositoryReadOnlyException;
 use ByJG\MicroOrm\FieldMapping;
 use ByJG\MicroOrm\Literal;
@@ -407,8 +408,7 @@ public function testDeleteLiteral()
 
     public function testDelete2()
     {
-        $query = DeleteQuery::getInstance()
-            ->table($this->userMapper->getTable())
+        $query = $this->userMapper->getDeleteQuery()
             ->where('name like :name', ['name'=>'Jane%']);
 
         $this->repository->deleteByQuery($query);
@@ -424,8 +424,7 @@ public function testDelete2()
 
     public function testGetByQueryNone()
     {
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>1000])
             ->orderBy(['property']);
 
@@ -437,8 +436,7 @@ public function testGetByQueryNone()
 
     public function testGetByQueryOne()
     {
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>3])
             ->orderBy(['property']);
 
@@ -504,8 +502,7 @@ public function testFilterInTwo()
      */
     public function testGetScalar()
     {
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->fields(['property'])
             ->where('iduser = :id', ['id'=>3]);
 
@@ -517,8 +514,7 @@ public function testGetScalar()
 
     public function testGetByQueryMoreThanOne()
     {
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>1])
             ->orderBy(['property']);
 
@@ -536,8 +532,7 @@ public function testGetByQueryMoreThanOne()
 
     public function testJoin()
     {
-        $query = new Query();
-        $query->table($this->userMapper->getTable())
+        $query = $this->userMapper->getQuery()
             ->fields([
                 'users.id',
                 'users.name',
@@ -570,8 +565,7 @@ public function testJoin()
 
     public function testLeftJoin()
     {
-        $query = new Query();
-        $query->table($this->userMapper->getTable())
+        $query = $this->userMapper->getQuery()
             ->fields([
                 'users.id',
                 'users.name',
@@ -596,8 +590,7 @@ public function testLeftJoin()
 
     public function testTop()
     {
-        $query = Query::getInstance()
-            ->table($this->userMapper->getTable())
+        $query = $this->userMapper->getQuery()
             ->top(1);
 
         $result = $this->repository->getByQuery($query);
@@ -611,8 +604,7 @@ public function testTop()
 
     public function testLimit()
     {
-        $query = Query::getInstance()
-            ->table($this->userMapper->getTable())
+        $query = $this->userMapper->getQuery()
             ->limit(1, 1);
 
         $result = $this->repository->getByQuery($query);
@@ -626,12 +618,11 @@ public function testLimit()
 
     public function testQueryRaw()
     {
-        $query = Query::getInstance()
+        $query = $this->userMapper->getQuery()
             ->fields([
                 "name",
                 "julianday('2020-06-28') - julianday(createdate) as days"
             ])
-            ->table($this->userMapper->getTable())
             ->limit(1, 1);
 
         $result = $this->repository->getByQuery($query);
@@ -699,8 +690,7 @@ public function getObserverdTable(): string
 
 
         // This update has an observer, and you change the `test` variable
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>3])
             ->orderBy(['property']);
 
@@ -798,12 +788,38 @@ public function getObserverdTable(): string
         $this->assertTrue($this->test);
     }
 
+    public function testAddSameObserverTwice()
+    {
+        $this->test = null;
+
+        $class = new class($this->infoMapper->getTable(), $this->repository, $this) implements ObserverProcessorInterface {
+
+            protected $table;
+            public function __construct($table, $parentRepository, $parent)
+            {
+                $this->table = $table;
+            }
+
+            public function process(ObserverData $observerData)
+            {
+            }
+
+            public function getObserverdTable(): string
+            {
+                return $this->table;
+            }
+        }        ;
+        $this->repository->addObserver($class);
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage("Observer already exists");
+        $this->repository->addObserver($class);
+    }
 
     public function testConstraintDifferentValues()
     {
         // This update has an observer, and you change the `test` variable
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>3])
             ->orderBy(['property']);
 
@@ -826,8 +842,7 @@ public function testConstraintSameValues()
         $this->expectExceptionMessage("You are not updating the property 'value'");
 
         // This update has an observer, and you change the `test` variable
-        $query = new Query();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQuery()
             ->where('iduser = :id', ['id'=>3])
             ->orderBy(['property']);
 
@@ -845,8 +860,7 @@ public function testConstraintSameValues()
 
     public function testQueryBasic()
     {
-        $query = new QueryBasic();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQueryBasic()
             ->where('iduser = :id', ['id'=>3]);
 
         $infoRepository = new Repository($this->dbDriver, $this->infoMapper);
@@ -861,12 +875,10 @@ public function testQueryBasic()
 
     public function testUnion()
     {
-        $query = new QueryBasic();
-        $query->table($this->infoMapper->getTable())
+        $query = $this->infoMapper->getQueryBasic()
             ->where('id = :id1', ['id1'=>3]);
 
-        $query2 = new QueryBasic();
-        $query2->table($this->infoMapper->getTable())
+        $query2 = $this->infoMapper->getQueryBasic()
             ->where('id = :id2', ['id2'=>1]);