diff --git a/ml-algorithms/src/test/java/org/opensearch/ml/engine/MLEngineTest.java b/ml-algorithms/src/test/java/org/opensearch/ml/engine/MLEngineTest.java
index 85951820e4..9d4710305f 100644
--- a/ml-algorithms/src/test/java/org/opensearch/ml/engine/MLEngineTest.java
+++ b/ml-algorithms/src/test/java/org/opensearch/ml/engine/MLEngineTest.java
@@ -11,6 +11,7 @@
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
+import org.mockito.Mock;
 import org.mockito.MockedStatic;
 import org.mockito.Mockito;
 import org.opensearch.core.common.io.stream.StreamOutput;
@@ -41,6 +42,7 @@
 import java.util.UUID;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
 import static org.opensearch.ml.engine.helper.LinearRegressionHelper.constructLinearRegressionPredictionDataFrame;
 import static org.opensearch.ml.engine.helper.LinearRegressionHelper.constructLinearRegressionTrainDataFrame;
 import static org.opensearch.ml.engine.helper.MLTestHelper.constructTestDataFrame;
@@ -68,6 +70,24 @@ public void testPrebuiltModelPath() {
         assertEquals("https://artifacts.opensearch.org/models/ml-models/huggingface/sentence-transformers/msmarco-distilbert-base-tas-b/1.0.1/torch_script/config.json", prebuiltModelConfigPath);
     }
 
+    @Test
+    public void testGetDeployModelZipPath() {
+        String modelId = "test_id";
+        String modelName = "huggingface/sentence-transformers/msmarco-distilbert-base-tas-b";
+        String modelZipPath = mlEngine.getDeployModelZipPath(modelId, modelName);
+        assertEquals(mlEngine.getMlCachePath() + Path.of("/models_cache/deploy/test_id/huggingface/sentence-transformers/msmarco-distilbert-base-tas-b.zip").toString(), modelZipPath);
+    }
+
+    @Test
+    public void testGetDeployModelChunkPath() {
+        String modelId = "test_id";
+        for (int i = 1; i <= 10; i++) {
+            Integer chunkNum = i;
+            Path chunkPath = mlEngine.getDeployModelChunkPath(modelId, chunkNum);
+            assertEquals(Path.of(mlEngine.getMlCachePath().toString() + "/models_cache/deploy/test_id/chunks/" + chunkNum.toString()), chunkPath);
+        }
+    }
+
     @Test
     public void predictKMeans() {
         MLModel model = trainKMeansModel();
@@ -142,6 +162,33 @@ public void train_NullInput() {
         }
     }
 
+    @Test
+    public void testTrainNullTrainable() {
+        exceptionRule.expect(IllegalArgumentException.class);
+        MLInput mlInput = Mockito.mock(MLInput.class);
+        when(mlInput.getAlgorithm()).thenReturn(FunctionName.LINEAR_REGRESSION);
+        when(MLEngineClassLoader.initInstance(mlInput.getAlgorithm(), mlInput.getParameters(), MLAlgoParams.class)).thenReturn(null);
+        mlEngine.train(mlInput);
+    }
+
+    @Test
+    public void predictNullPredictable() {
+        exceptionRule.expect(IllegalArgumentException.class);
+        MLInput mlInput = Mockito.mock(MLInput.class);
+        MLModel mlModel = Mockito.mock(MLModel.class);
+        when(mlInput.getAlgorithm()).thenReturn(FunctionName.LINEAR_REGRESSION);
+        when(MLEngineClassLoader.initInstance(mlInput.getAlgorithm(), mlInput.getParameters(), MLAlgoParams.class)).thenReturn(null);
+        mlEngine.predict(mlInput, mlModel);
+    }
+
+    @Test
+    public void trainAndPredictNullTrainable() {
+        exceptionRule.expect(IllegalArgumentException.class);
+        MLInput mlInput = Mockito.mock(MLInput.class);
+        when(mlInput.getAlgorithm()).thenReturn(FunctionName.LINEAR_REGRESSION);
+        when(MLEngineClassLoader.initInstance(mlInput.getAlgorithm(), mlInput.getParameters(), MLAlgoParams.class)).thenReturn(null);
+        mlEngine.trainAndPredict(mlInput);
+    }
     //TODO: fix mockito error
     @Ignore
     @Test