diff --git a/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidator.java b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidator.java
index a126bcf7..cb6a2220 100644
--- a/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidator.java
+++ b/src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidator.java
@@ -121,7 +121,8 @@ public abstract class HsHostingAssetEntityValidator extends HsEntityValidator<Hs
 
     private List<String> validateIdentifierPattern(final HsHostingAssetEntity assetEntity) {
         final var expectedIdentifierPattern = identifierPattern(assetEntity);
-        if (!expectedIdentifierPattern.matcher(assetEntity.getIdentifier()).matches()) {
+        if (assetEntity.getIdentifier() == null ||
+                !expectedIdentifierPattern.matcher(assetEntity.getIdentifier()).matches()) {
             return List.of("'identifier' expected to match '"+expectedIdentifierPattern+"', but is '" + assetEntity.getIdentifier() + "'");
         }
         return Collections.emptyList();
diff --git a/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidatorRegistryUnitTest.java b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidatorRegistryUnitTest.java
new file mode 100644
index 00000000..32c098f3
--- /dev/null
+++ b/src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsHostingAssetEntityValidatorRegistryUnitTest.java
@@ -0,0 +1,64 @@
+package net.hostsharing.hsadminng.hs.hosting.asset.validators;
+
+import net.hostsharing.hsadminng.hs.booking.item.HsBookingItemEntity;
+import net.hostsharing.hsadminng.hs.booking.item.HsBookingItemType;
+import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetEntity;
+import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
+import static org.assertj.core.api.Assertions.entry;
+
+class HsHostingAssetEntityValidatorRegistryUnitTest {
+
+    @Test
+    void forTypeWithUnknownTypeThrowsException() {
+        // when
+        final var thrown = catchThrowable(() -> {
+            HsHostingAssetEntityValidatorRegistry.forType(null);
+        });
+
+        // then
+        assertThat(thrown).hasMessage("no validator found for type null");
+    }
+
+    @Test
+    void typesReturnsAllImplementedTypes() {
+        // when
+        final var types = HsHostingAssetEntityValidatorRegistry.types();
+
+        // then
+        // TODO.test: when all types are implemented, replace with set of all types:
+        // assertThat(types).isEqualTo(EnumSet.allOf(HsHostingAssetType.class));
+        // also remove "Implemented" from the test method name.
+        assertThat(types).containsExactlyInAnyOrder(
+                HsHostingAssetType.CLOUD_SERVER,
+                HsHostingAssetType.MANAGED_SERVER,
+                HsHostingAssetType.MANAGED_WEBSPACE,
+                HsHostingAssetType.UNIX_USER
+        );
+    }
+
+    @Test
+    void validatedDoesNotThrowAnExceptionForValidEntity() {
+        final var givenBookingItem = HsBookingItemEntity.builder()
+                .type(HsBookingItemType.CLOUD_SERVER)
+                .resources(Map.ofEntries(
+                        entry("CPUs", 4),
+                        entry("RAM", 20),
+                        entry("SSD", 50),
+                        entry("Traffic", 250)
+                ))
+                .build();
+        final var validEntity = HsHostingAssetEntity.builder()
+                .type(HsHostingAssetType.CLOUD_SERVER)
+                .bookingItem(givenBookingItem)
+                .identifier("vm1234")
+                .caption("some valid cloud server")
+                .build();
+        HsHostingAssetEntityValidatorRegistry.validated(validEntity);
+    }
+}