Update.

test/dataset/auto_schema.wren

@@ -0,0 +1,20 @@
+// retoor <retoor@molodetz.nl>
+
+import "dataset" for Dataset
+
+var ds = Dataset.memory()
+
+var users = ds["users"]
+users.insert({"name": "Alice"})
+
+var cols1 = users.columns
+System.print(cols1.containsKey("uid")) // expect: true
+System.print(cols1.containsKey("name")) // expect: true
+System.print(cols1.containsKey("email")) // expect: false
+
+users.insert({"name": "Bob", "email": "bob@example.com"})
+
+var cols2 = users.columns
+System.print(cols2.containsKey("email")) // expect: true
+
+ds.close()