diff --git a/teaql-core/src/test/java/io/teaql/core/EntityChangeSetTest.java b/teaql-core/src/test/java/io/teaql/core/EntityChangeSetTest.java
new file mode 100644
index 0000000..d442c28
--- /dev/null
+++ b/teaql-core/src/test/java/io/teaql/core/EntityChangeSetTest.java
@@ -0,0 +1,97 @@
+package io.teaql.core;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Map;
+import java.util.Set;
+import org.junit.Test;
+
+public class EntityChangeSetTest {
+
+    private static final EntityKey ORDER = new EntityKey("Order", 1L);
+    private static final EntityKey OTHER_ORDER = new EntityKey("Order", 2L);
+
+    @Test
+    public void newChangeSetIsEmpty() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+
+        assertTrue(changeSet.isEmpty());
+        assertTrue(changeSet.changes().isEmpty());
+    }
+
+    @Test
+    public void setMakesFieldValueReadable() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+
+        changeSet.set(ORDER, "status", "PAID");
+
+        assertFalse(changeSet.isEmpty());
+        assertEquals("PAID", changeSet.get(ORDER, "status"));
+        assertNull(changeSet.get(ORDER, "missing"));
+    }
+
+    @Test
+    public void settingSameFieldKeepsLatestValue() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+        changeSet.set(ORDER, "status", "CREATED");
+
+        changeSet.set(ORDER, "status", "PAID");
+
+        assertEquals("PAID", changeSet.get(ORDER, "status"));
+        assertEquals(1, changeSet.fieldNames(ORDER).size());
+    }
+
+    @Test
+    public void changesForDifferentEntitiesRemainIsolated() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+
+        changeSet.set(ORDER, "status", "PAID");
+        changeSet.set(OTHER_ORDER, "status", "CANCELLED");
+
+        assertEquals("PAID", changeSet.get(ORDER, "status"));
+        assertEquals("CANCELLED", changeSet.get(OTHER_ORDER, "status"));
+    }
+
+    @Test
+    public void fieldNamesContainOnlyFieldsForRequestedEntity() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+        changeSet.set(ORDER, "status", "PAID");
+        changeSet.set(ORDER, "total", 100L);
+        changeSet.set(OTHER_ORDER, "comment", "other");
+
+        assertEquals(Set.of("status", "total"), changeSet.fieldNames(ORDER));
+        assertEquals(Set.of("comment"), changeSet.fieldNames(OTHER_ORDER));
+        assertTrue(changeSet.fieldNames(new EntityKey("Order", 3L)).isEmpty());
+    }
+
+    @Test
+    public void clearEntityRemovesOnlyRequestedEntity() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+        changeSet.set(ORDER, "status", "PAID");
+        changeSet.set(OTHER_ORDER, "status", "CANCELLED");
+
+        changeSet.clearEntity(ORDER);
+
+        assertNull(changeSet.get(ORDER, "status"));
+        assertEquals("CANCELLED", changeSet.get(OTHER_ORDER, "status"));
+        assertFalse(changeSet.isEmpty());
+    }
+
+    @Test
+    public void exposedCollectionsAreReadOnly() {
+        EntityChangeSet changeSet = new EntityChangeSet();
+        changeSet.set(ORDER, "status", "PAID");
+
+        Map<EntityKey, Map<String, Object>> changes = changeSet.changes();
+        Set<String> fieldNames = changeSet.fieldNames(ORDER);
+
+        assertThrows(
+                UnsupportedOperationException.class,
+                () -> changes.put(OTHER_ORDER, Map.of("status", "CANCELLED")));
+        assertThrows(UnsupportedOperationException.class, () -> fieldNames.add("total"));
+    }
+}