diff --git a/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/ClassificationMetricsFncSpec.scala b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/ClassificationMetricsFncSpec.scala
new file mode 100644
index 00000000000..5b1cbd1b87a
--- /dev/null
+++ b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/ClassificationMetricsFncSpec.scala
@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.texera.amber.operator.machineLearning.Scorer
+
+import org.apache.texera.amber.util.JSONUtils.objectMapper
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class ClassificationMetricsFncSpec extends AnyFlatSpec with Matchers {
+
+  "classificationMetricsFnc" should "map each constant to its wire value" in {
+    classificationMetricsFnc.accuracy.getName shouldBe "Accuracy"
+    classificationMetricsFnc.precisionScore.getName shouldBe "Precision Score"
+    classificationMetricsFnc.recallScore.getName shouldBe "Recall Score"
+    classificationMetricsFnc.f1Score.getName shouldBe "F1 Score"
+    classificationMetricsFnc.values() should have length 4
+  }
+
+  "classificationMetricsFnc" should "round-trip through Jackson using its wire value" in {
+    objectMapper.writeValueAsString(classificationMetricsFnc.f1Score) shouldBe "\"F1 Score\""
+    objectMapper.readValue(
+      "\"F1 Score\"",
+      classOf[classificationMetricsFnc]
+    ) shouldBe classificationMetricsFnc.f1Score
+  }
+}
diff --git a/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/RegressionMetricsFncSpec.scala b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/RegressionMetricsFncSpec.scala
new file mode 100644
index 00000000000..6d822f46d6f
--- /dev/null
+++ b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/machineLearning/Scorer/RegressionMetricsFncSpec.scala
@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.texera.amber.operator.machineLearning.Scorer
+
+import org.apache.texera.amber.util.JSONUtils.objectMapper
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class RegressionMetricsFncSpec extends AnyFlatSpec with Matchers {
+
+  "regressionMetricsFnc" should "map each constant to its wire value" in {
+    regressionMetricsFnc.mse.getName shouldBe "MSE"
+    regressionMetricsFnc.rmse.getName shouldBe "RMSE"
+    regressionMetricsFnc.mae.getName shouldBe "MAE"
+    regressionMetricsFnc.r2.getName shouldBe "R2"
+    regressionMetricsFnc.values() should have length 4
+  }
+
+  "regressionMetricsFnc" should "round-trip through Jackson using its wire value" in {
+    objectMapper.writeValueAsString(regressionMetricsFnc.rmse) shouldBe "\"RMSE\""
+    objectMapper.readValue(
+      "\"RMSE\"",
+      classOf[regressionMetricsFnc]
+    ) shouldBe regressionMetricsFnc.rmse
+  }
+}
diff --git a/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/sort/SortPreferenceSpec.scala b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/sort/SortPreferenceSpec.scala
new file mode 100644
index 00000000000..53c78ab8e76
--- /dev/null
+++ b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/sort/SortPreferenceSpec.scala
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.texera.amber.operator.sort
+
+import org.apache.texera.amber.util.JSONUtils.objectMapper
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class SortPreferenceSpec extends AnyFlatSpec with Matchers {
+
+  "SortPreference" should "expose exactly the ascending and descending constants" in {
+    SortPreference.values() should have length 2
+    SortPreference.valueOf("ASC") shouldBe SortPreference.ASC
+    SortPreference.valueOf("DESC") shouldBe SortPreference.DESC
+  }
+
+  "SortPreference" should "round-trip through Jackson using its constant name" in {
+    objectMapper.writeValueAsString(SortPreference.ASC) shouldBe "\"ASC\""
+    objectMapper.readValue("\"DESC\"", classOf[SortPreference]) shouldBe SortPreference.DESC
+  }
+}