diff --git a/src/Link.php b/src/Link.php
index cb1e088..a97fa30 100644
--- a/src/Link.php
+++ b/src/Link.php
@@ -189,6 +189,7 @@ class Link {
   public function close() {
     if ($this->_link)
       @ldap_close($this->_link);
+    $this -> _link = false;
   }
 
 }
diff --git a/tests/LinkTest.php b/tests/LinkTest.php
new file mode 100644
index 0000000..adc1894
--- /dev/null
+++ b/tests/LinkTest.php
@@ -0,0 +1,466 @@
+<?php
+declare(strict_types=1);
+use \Mockery\Adapter\Phpunit\MockeryTestCase;
+use PHPUnit\Extension\FunctionMocker;
+use EesyLDAP\Link;
+
+
+/**
+ * @covers \EesyLDAP\Link
+ */
+final class LinkTest extends MockeryTestCase {
+
+  /**
+   * @var FunctionMocker
+   */
+  protected $func;
+
+  public function setUp(): void {
+    $this->func = FunctionMocker::start($this, 'EesyLDAP')
+                  ->mockFunction('ldap_connect')
+                  ->mockFunction('ldap_start_tls')
+                  ->mockFunction('ldap_errno')
+                  ->mockFunction('ldap_err2str')
+                  ->mockFunction('ldap_bind')
+                  ->mockFunction('ldap_set_option')
+                  ->mockFunction('ldap_list')
+                  ->mockFunction('ldap_read')
+                  ->mockFunction('ldap_search')
+                  ->mockFunction('ldap_get_entries')
+                  ->mockFunction('ldap_close')
+                  ->getMock();
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::connect
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testConnect() {
+    $link = new Link();
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue(true));
+    $link->connect('ldap://host', 389);
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::connect
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testConnectNoPort() {
+    $link = new Link();
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::start_tls
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testStartTLS() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_start_tls')
+               ->with($ldap_link)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->start_tls());
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::start_tls
+   */
+  public function testStartTLSNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->start_tls());
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::errno
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testErrNo() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $error = 186;
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_errno')
+               ->with($ldap_link)
+               ->will($this->returnValue($error));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertEquals($error, $link->errno());
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::errno
+   */
+  public function testErrNoNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->errno());
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::err2str
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testErr2Str() {
+    $link = new Link();
+    $error = 186;
+    $error_msg = 'oups';
+    $this->func->expects($this->once())
+               ->method('ldap_err2str')
+               ->with($error)
+               ->will($this->returnValue($error_msg));
+    $this->assertEquals($error_msg, $link->err2str($error));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::bind
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testBind() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $dn = 'cn=test';
+    $password = 'secret';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_bind')
+               ->with($ldap_link, $dn, $password)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->bind($dn, $password));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::bind
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testBindNoParams() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_bind')
+               ->with($ldap_link, null, null)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->bind());
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::errno
+   */
+  public function testBindNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->bind('cn=test', 'secret'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::set_option
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testSetOption() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $option = 10;
+    $value = 'value';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_set_option')
+               ->with($ldap_link, $option, $value)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->set_option($option, $value));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::set_option
+   */
+  public function testSetOptionNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->set_option(10, 'test'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::list
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testList() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $attributes = array('cn');
+    $attributes_only=1;
+    $sizelimit = 10;
+    $timelimit = 30;
+    $deref =  LDAP_DEREF_ALWAYS;
+	  $controls = array();
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_list')
+               ->with(
+                 $ldap_link, $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit,
+                 $deref, $controls)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue(
+      $link->list(
+        $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit, $deref, $controls
+      )
+    );
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::list
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testListWithMinimalParameters() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_list')
+               ->with($ldap_link, $base, $filter, [], 0, -1, -1,  LDAP_DEREF_NEVER, [])
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->list($base, $filter));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::list
+   */
+  public function testListNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->list('o=example', 'test=value'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::read
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testRead() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $attributes = array('cn');
+    $attributes_only=1;
+    $sizelimit = 10;
+    $timelimit = 30;
+    $deref =  LDAP_DEREF_ALWAYS;
+	  $controls = array();
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_read')
+               ->with(
+                 $ldap_link, $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit,
+                 $deref, $controls)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue(
+      $link->read(
+        $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit, $deref, $controls
+      )
+    );
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::read
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testReadWithMinimalParameters() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_read')
+               ->with($ldap_link, $base, $filter, [], 0, -1, -1,  LDAP_DEREF_NEVER, [])
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->read($base, $filter));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::read
+   */
+  public function testReadNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->read('o=example', 'test=value'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::search
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testSearch() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $attributes = array('cn');
+    $attributes_only=1;
+    $sizelimit = 10;
+    $timelimit = 30;
+    $deref =  LDAP_DEREF_ALWAYS;
+	  $controls = array();
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_search')
+               ->with(
+                 $ldap_link, $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit,
+                 $deref, $controls)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue(
+      $link->search(
+        $base, $filter, $attributes, $attributes_only, $sizelimit, $timelimit, $deref, $controls
+      )
+    );
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::search
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testSearchWithMinimalParameters() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $base = 'o=example';
+    $filter = 'cn=test';
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_search')
+               ->with($ldap_link, $base, $filter, [], 0, -1, -1,  LDAP_DEREF_NEVER, [])
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $this->assertTrue($link->search($base, $filter));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::search
+   */
+  public function testSearchNoLink() {
+    $link = new Link();
+    $this->assertFalse($link->search('o=example', 'test=value'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::get_entries
+   * @runInSeparateProcess
+   * @preserveGlobalState disabled
+   */
+  public function testGetEntries() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $search_ref = 'search_ref';
+    $expected_result = array('test');
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_get_entries')
+               ->with($ldap_link, $search_ref)
+               ->will($this->returnValue($expected_result));
+    $this->assertTrue($link->connect('ldap://host'));
+    // @phpstan-ignore-next-line
+    $this->assertEquals($expected_result, $link->get_entries($search_ref));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::get_entries
+   */
+  public function testGetEntriesNoLink() {
+    $link = new Link();
+    // @phpstan-ignore-next-line
+    $this->assertFalse($link->get_entries('search_ref'));
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::close
+   */
+  public function testClose() {
+    $link = new Link();
+    $ldap_link = 'ldap_link';
+    $search_ref = 'search_ref';
+    $expected_result = array('test');
+    $this->func->expects($this->once())
+               ->method('ldap_connect')
+               ->with('ldap://host', 389)
+               ->will($this->returnValue($ldap_link));
+    $this->func->expects($this->once())
+               ->method('ldap_close')
+               ->with($ldap_link)
+               ->will($this->returnValue(true));
+    $this->assertTrue($link->connect('ldap://host'));
+    $link->close();
+  }
+
+  /**
+   * @covers \EesyLDAP\Link::close
+   */
+  public function testCloseNoLink() {
+    $link = new Link();
+    $link->close();
+  }
+}