diff --git a/tests/php-unit-tests/unitary-tests/core/UniquenessMessageTest.php b/tests/php-unit-tests/unitary-tests/core/UniquenessMessageTest.php
new file mode 100644
index 000000000..03495dfb5
--- /dev/null
+++ b/tests/php-unit-tests/unitary-tests/core/UniquenessMessageTest.php
@@ -0,0 +1,95 @@
+<?php
+
+
+namespace Combodo\iTop\Test\UnitTest\Core;
+
+use Combodo\iTop\Test\UnitTest\ItopDataTestCase;
+use Exception;
+use lnkPersonToTeam;
+use Person;
+use Team;
+
+/**
+ * Class UniquenessMessageTest
+ *
+ * @runTestsInSeparateProcesses
+ * @preserveGlobalState disabled
+ * @backupGlobals disabled
+ *
+ * @package Combodo\iTop\Test\UnitTest\Core
+ */
+class UniquenessMessageTest extends ItopDataTestCase
+{
+
+	/** @inheritdoc */
+	protected function setUp(): void
+	{
+		parent::setUp();
+	}
+
+	/**
+	 * Create a Team in database
+	 *
+	 * @param int $iNum
+	 *
+	 * @return Team
+	 * @throws \Exception
+	 */
+	protected function CreateTeam($iNum)
+	{
+		/** @var Team $oTeam */
+		$oTeam = $this->createObject('Team', array(
+			'name'   => 'Name_'.$iNum,
+			'org_id' => $this->getTestOrgId(),
+		));
+		$this->debug("Created Team {$oTeam->GetName()} ({$oTeam->GetKey()})");
+
+		return $oTeam;
+	}
+
+	/**
+	 *
+	 * @param Person $oPerson
+	 * @param Team $oTeam
+	 *
+	 * @return lnkPersonToTeam
+	 * @throws Exception
+	 */
+	protected function AddPersonToTeam($oPerson, $oTeam)
+	{
+		$oNewLink = new lnkPersonToTeam();
+		$oNewLink->Set('person_id', $oPerson->GetKey());
+		$oPersons = $oTeam->Get('persons_list');
+		$oPersons->AddItem($oNewLink);
+		$oTeam->Set('persons_list', $oPersons);
+
+		return $oNewLink;
+	}
+
+	/**
+	 * testUniquenessRuleMessage.
+	 *
+	 * N°5916 - Generic message on Link Uniqueness rules
+	 */
+	public function testUniquenessRuleMessage()
+	{
+		$this->CreateTestOrganization();
+		$oPerson = $this->CreatePerson(1);
+		$oTeam = $this->CreateTeam(1);
+		$oLnk = $this->AddPersonToTeam($oPerson, $oTeam);
+		$oTeam->DBUpdate();
+
+		// Default error
+		$sMessage = $this->InvokeNonPublicMethod(Person::class, 'GetUniquenessRuleMessage', $oPerson, ['no_duplicate']);
+		$this->assertEquals("Uniqueness rule 'no_duplicate' in error", $sMessage);
+
+		// Generic message
+		$sMessage = $this->InvokeNonPublicMethod(lnkPersonToTeam::class, 'GetUniquenessRuleMessage', $oLnk, ['no_duplicate']);
+		$this->assertEquals("Team: Name_1 is already linked to Person: Test Person_1, duplicates are not allowed on this relation.", $sMessage);
+
+		// Specific message
+		$sMessage = $this->InvokeNonPublicMethod(Person::class, 'GetUniquenessRuleMessage', $oPerson, ['employee_number']);
+		$this->assertEquals("there is already a person in 'UnitTestOrganization' organization with the same employee number", $sMessage);
+	}
+
+}