diff --git a/src/main/java/com/sitepark/ies/userrepository/core/domain/entity/Identifier.java b/src/main/java/com/sitepark/ies/userrepository/core/domain/entity/Identifier.java
index 9575752..4f5980b 100644
--- a/src/main/java/com/sitepark/ies/userrepository/core/domain/entity/Identifier.java
+++ b/src/main/java/com/sitepark/ies/userrepository/core/domain/entity/Identifier.java
@@ -96,7 +96,7 @@ public boolean equals(Object o) {
 	@Override
 	public String toString() {
 		if (this.id != null) {
-			return this.id.toString();
+			return this.id;
 		}
 		return this.anchor.toString();
 	}
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/AccessTokenTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/AccessTokenTest.java
index 74b0ecc..1dcfa32 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/AccessTokenTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/AccessTokenTest.java
@@ -21,9 +21,14 @@
 import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
 @SuppressWarnings("PMD.TooManyMethods")
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class AccessTokenTest {
 
 	private static final ZoneId ZONE_ID = ZoneId.of( "Europe/Berlin" );
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/IdentifierTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/IdentifierTest.java
index 3c9414a..aec63e5 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/IdentifierTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/IdentifierTest.java
@@ -7,8 +7,13 @@
 
 import org.junit.jupiter.api.Test;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class IdentifierTest {
 
 	@Test
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/RoleTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/RoleTest.java
index bb56362..8acf465 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/RoleTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/RoleTest.java
@@ -11,6 +11,10 @@
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class RoleTest {
 
 	private static final String TEST_ROLE_NAME = "ADMINISTRATOR";
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserTest.java
index bbd4a36..971d61e 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserTest.java
@@ -20,6 +20,7 @@
 import com.sitepark.ies.userrepository.core.domain.entity.role.Ref;
 import com.sitepark.ies.userrepository.core.domain.entity.role.UserLevelRoles;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
 @SuppressWarnings({
@@ -27,6 +28,11 @@
 	"PMD.TooManyMethods",
 	"PMD.GodClass"
 })
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL",
+	"NP_NULL_PARAM_DEREF_ALL_TARGETS_DANGEROUS"
+})
 class UserTest {
 
 	private static Identity TEST_IDENTITY = LdapIdentity.builder()
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserValidityTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserValidityTest.java
index 8e442b7..dab4d71 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserValidityTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/UserValidityTest.java
@@ -19,6 +19,7 @@
 import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
 @SuppressWarnings({
@@ -26,6 +27,10 @@
 	"PMD.AvoidDuplicateLiterals",
 	"PMD.TooManyMethods"
 })
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class UserValidityTest {
 
 	private static final ZoneId ZONE_ID = ZoneId.of( "Europe/Berlin" );
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/identity/LdapIdentityTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/identity/LdapIdentityTest.java
index f353d4b..fd59a15 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/identity/LdapIdentityTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/identity/LdapIdentityTest.java
@@ -11,9 +11,14 @@
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
 @SuppressWarnings("PMD.TooManyMethods")
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class LdapIdentityTest {
 
 	private static final String USER_DN = "userdn";
diff --git a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/role/RefTest.java b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/role/RefTest.java
index 96a15ed..1adfe3a 100644
--- a/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/role/RefTest.java
+++ b/src/test/java/com/sitepark/ies/userrepository/core/domain/entity/role/RefTest.java
@@ -9,8 +9,13 @@
 
 import com.sitepark.ies.userrepository.core.domain.entity.Anchor;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import nl.jqno.equalsverifier.EqualsVerifier;
 
+@SuppressFBWarnings({
+	"PI_DO_NOT_REUSE_PUBLIC_IDENTIFIERS_CLASS_NAMES",
+	"NP_NULL_PARAM_DEREF_NONVIRTUAL"
+})
 class RefTest {
 
 	@Test