diff --git a/core/src/test/java/google/registry/model/ImmutableObjectSubject.java b/core/src/test/java/google/registry/model/ImmutableObjectSubject.java
new file mode 100644
index 000000000..c3fc5bd03
--- /dev/null
+++ b/core/src/test/java/google/registry/model/ImmutableObjectSubject.java
@@ -0,0 +1,95 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.model;
+
+import static com.google.common.truth.Truth.assertAbout;
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.truth.Correspondence;
+import com.google.common.truth.Correspondence.BinaryPredicate;
+import com.google.common.truth.FailureMetadata;
+import com.google.common.truth.SimpleSubjectBuilder;
+import com.google.common.truth.Subject;
+import java.lang.reflect.Field;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import javax.annotation.Nullable;
+
+/** Truth subject for asserting things about ImmutableObjects that are not built in. */
+public final class ImmutableObjectSubject extends Subject {
+
+  private final ImmutableObject actual;
+
+  protected ImmutableObjectSubject(FailureMetadata failureMetadata, ImmutableObject actual) {
+    super(failureMetadata, actual);
+    this.actual = actual;
+  }
+
+  public void isEqualExceptFields(ImmutableObject expected, String... ignoredFields) {
+    Map<Field, Object> actualFields = filterFields(actual, ignoredFields);
+    Map<Field, Object> expectedFields = filterFields(expected, ignoredFields);
+    assertThat(actualFields).containsExactlyEntriesIn(expectedFields);
+  }
+
+  public static Correspondence<ImmutableObject, ImmutableObject> immutableObjectCorrespondence(
+      String... ignoredFields) {
+    return Correspondence.from(
+        new ImmutableObjectBinaryPredicate(ignoredFields), "has all relevant fields equal to");
+  }
+
+  public static SimpleSubjectBuilder<ImmutableObjectSubject, ImmutableObject>
+      assertAboutImmutableObjects() {
+    return assertAbout(ImmutableObjectSubject::new);
+  }
+
+  private static class ImmutableObjectBinaryPredicate
+      implements BinaryPredicate<ImmutableObject, ImmutableObject> {
+
+    private final String[] ignoredFields;
+
+    private ImmutableObjectBinaryPredicate(String... ignoredFields) {
+      this.ignoredFields = ignoredFields;
+    }
+
+    @Override
+    public boolean apply(@Nullable ImmutableObject actual, @Nullable ImmutableObject expected) {
+      if (actual == null && expected == null) {
+        return true;
+      }
+      if (actual == null || expected == null) {
+        return false;
+      }
+      Map<Field, Object> actualFields = filterFields(actual, ignoredFields);
+      Map<Field, Object> expectedFields = filterFields(expected, ignoredFields);
+      return Objects.equals(actualFields, expectedFields);
+    }
+  }
+
+  private static Map<Field, Object> filterFields(
+      ImmutableObject original, String... ignoredFields) {
+    ImmutableSet<String> ignoredFieldSet = ImmutableSet.copyOf(ignoredFields);
+    Map<Field, Object> originalFields = ModelUtils.getFieldValues(original);
+    // don't use ImmutableMap or a stream->collect model since we can have nulls
+    Map<Field, Object> result = new LinkedHashMap<>();
+    for (Map.Entry<Field, Object> entry : originalFields.entrySet()) {
+      if (!ignoredFieldSet.contains(entry.getKey().getName())) {
+        result.put(entry.getKey(), entry.getValue());
+      }
+    }
+    return result;
+  }
+}
diff --git a/core/src/test/java/google/registry/model/history/HostHistoryTest.java b/core/src/test/java/google/registry/model/history/HostHistoryTest.java
index df6e268e5..3ded202a3 100644
--- a/core/src/test/java/google/registry/model/history/HostHistoryTest.java
+++ b/core/src/test/java/google/registry/model/history/HostHistoryTest.java
@@ -14,7 +14,7 @@
 
 package google.registry.model.history;
 
-import static com.google.common.truth.Truth.assertThat;
+import static google.registry.model.ImmutableObjectSubject.assertAboutImmutableObjects;
 import static google.registry.persistence.transaction.TransactionManagerFactory.jpaTm;
 import static google.registry.testing.SqlHelper.saveRegistrar;
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -74,14 +74,9 @@ public class HostHistoryTest extends EntityTestCase {
   }
 
   private void assertHostHistoriesEqual(HostHistory one, HostHistory two) {
-    // enough of the fields get changed during serialization that we can't depend on .equals()
-    assertThat(one.getClientId()).isEqualTo(two.getClientId());
-    assertThat(one.getHostRepoId()).isEqualTo(two.getHostRepoId());
-    assertThat(one.getBySuperuser()).isEqualTo(two.getBySuperuser());
-    assertThat(one.getRequestedByRegistrar()).isEqualTo(two.getRequestedByRegistrar());
-    assertThat(one.getReason()).isEqualTo(two.getReason());
-    assertThat(one.getTrid()).isEqualTo(two.getTrid());
-    assertThat(one.getType()).isEqualTo(two.getType());
-    assertThat(one.getHostBase().getHostName()).isEqualTo(two.getHostBase().getHostName());
+    assertAboutImmutableObjects().that(one).isEqualExceptFields(two, "hostBase");
+    assertAboutImmutableObjects()
+        .that(one.getHostBase())
+        .isEqualExceptFields(two.getHostBase(), "repoId");
   }
 }