diff --git a/build.gradle b/build.gradle
index 7efa4725..dcdd80df 100644
--- a/build.gradle
+++ b/build.gradle
@@ -208,12 +208,29 @@ task cucumberTestReport(type: TestReport) {
 
 pitest {
     targetClasses = ['org.hostsharing.hsadminng.*']
+
+    excludedClasses = [
+                        // Unit Testing Spring configurations makes little sense in most cases.
+                        'org.hostsharing.hsadminng.config.*',
+                        'org.hostsharing.hsadminng.ApplicationWebXml',
+                        'org.hostsharing.hsadminng.HsadminNgApp',
+
+                        // Unit testing this would need PowerMock and
+                        // blackbox testing of random values has little value.
+                        'org.hostsharing.hsadminng.service.util.RandomUtil',
+
+                        // The following are mostly generated classes,
+                        // as soon as we amend these, consider removing the exclude.
+                        'org.hostsharing.hsadminng.**Criteria',
+                        'org.hostsharing.hsadminng.aop.logging.*',
+                        'org.hostsharing.hsadminng.web.api.*' // API helpers, not the API itself
+                      ]
     threads = 2
 
-    // Do not set these limit even lower, they are already pretty bad values!
-    // 83%*78% means that only ~66% of the code is properly covered by automated tests.
-    mutationThreshold = 78
-    coverageThreshold = 83
+    // Do not set these limit lower! 90% each might sound good, but keep in mind:
+    // 90%*90% means that ~81% of the code are properly covered by automated tests.
+    mutationThreshold = 90
+    coverageThreshold = 90
 
     outputFormats = ['XML', 'HTML']
     timestampedReports = false
diff --git a/src/main/java/org/hostsharing/hsadminng/domain/Customer.java b/src/main/java/org/hostsharing/hsadminng/domain/Customer.java
index c7cb1495..08548949 100644
--- a/src/main/java/org/hostsharing/hsadminng/domain/Customer.java
+++ b/src/main/java/org/hostsharing/hsadminng/domain/Customer.java
@@ -195,16 +195,6 @@ public class Customer implements Serializable {
         return this;
     }
 
-    public Customer removeMembership(Membership membership) {
-        this.memberships.remove(membership);
-        membership.setCustomer(null);
-        return this;
-    }
-
-    public void setMemberships(Set<Membership> memberships) {
-        this.memberships = memberships;
-    }
-
     public Set<SepaMandate> getSepamandates() {
         return sepamandates;
     }
@@ -220,15 +210,6 @@ public class Customer implements Serializable {
         return this;
     }
 
-    public Customer removeSepamandate(SepaMandate sepaMandate) {
-        this.sepamandates.remove(sepaMandate);
-        sepaMandate.setCustomer(null);
-        return this;
-    }
-
-    public void setSepamandates(Set<SepaMandate> sepaMandates) {
-        this.sepamandates = sepaMandates;
-    }
     // jhipster-needle-entity-add-getters-setters - JHipster will add getters and setters here, do not remove
 
     @Override
diff --git a/src/main/java/org/hostsharing/hsadminng/domain/Membership.java b/src/main/java/org/hostsharing/hsadminng/domain/Membership.java
index d6e4e5bd..78ce7bff 100644
--- a/src/main/java/org/hostsharing/hsadminng/domain/Membership.java
+++ b/src/main/java/org/hostsharing/hsadminng/domain/Membership.java
@@ -129,16 +129,6 @@ public class Membership implements Serializable {
         return this;
     }
 
-    public Membership removeShare(Share share) {
-        this.shares.remove(share);
-        share.setMembership(null);
-        return this;
-    }
-
-    public void setShares(Set<Share> shares) {
-        this.shares = shares;
-    }
-
     public Set<Asset> getAssets() {
         return assets;
     }
@@ -154,16 +144,6 @@ public class Membership implements Serializable {
         return this;
     }
 
-    public Membership removeAsset(Asset asset) {
-        this.assets.remove(asset);
-        asset.setMembership(null);
-        return this;
-    }
-
-    public void setAssets(Set<Asset> assets) {
-        this.assets = assets;
-    }
-
     public Customer getCustomer() {
         return customer;
     }
diff --git a/src/test/java/org/hostsharing/hsadminng/service/dto/MembershipDTOTest.java b/src/test/java/org/hostsharing/hsadminng/service/dto/MembershipDTOTest.java
new file mode 100644
index 00000000..ffcec115
--- /dev/null
+++ b/src/test/java/org/hostsharing/hsadminng/service/dto/MembershipDTOTest.java
@@ -0,0 +1,15 @@
+package org.hostsharing.hsadminng.service.dto;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class MembershipDTOTest {
+
+    @Test
+    public void withShouldApplyCallback() {
+        final MembershipDTO actual = new MembershipDTO().with(m -> m.setRemark("Some Remark"));
+
+        assertThat(actual.getRemark()).isEqualTo("Some Remark");
+    }
+}