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diff --git a/core/src/test/java/org/elasticsearch/search/suggest/phrase/LinearInterpolationModelTests.java b/core/src/test/java/org/elasticsearch/search/suggest/phrase/LinearInterpolationModelTests.java
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+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.elasticsearch.search.suggest.phrase;
+
+import org.elasticsearch.search.suggest.phrase.PhraseSuggestionBuilder.LinearInterpolation;
+import org.elasticsearch.search.suggest.phrase.PhraseSuggestionBuilder.SmoothingModel;
+
+import static org.hamcrest.Matchers.instanceOf;
+
+public class LinearInterpolationModelTests extends SmoothingModelTestCase {
+
+    @Override
+    protected SmoothingModel createTestModel() {
+        double trigramLambda = randomDoubleBetween(0.0, 10.0, false);
+        double bigramLambda = randomDoubleBetween(0.0, 10.0, false);
+        double unigramLambda = randomDoubleBetween(0.0, 10.0, false);
+        // normalize so parameters sum to 1
+        double sum = trigramLambda + bigramLambda + unigramLambda;
+        return new LinearInterpolation(trigramLambda / sum, bigramLambda / sum, unigramLambda / sum);
+    }
+
+    /**
+     * mutate the given model so the returned smoothing model is different
+     */
+    @Override
+    protected LinearInterpolation createMutation(SmoothingModel input) {
+        LinearInterpolation original = (LinearInterpolation) input;
+        // swap two values permute original lambda values
+        switch (randomIntBetween(0, 2)) {
+        case 0:
+            // swap first two
+            return new LinearInterpolation(original.getBigramLambda(), original.getTrigramLambda(), original.getUnigramLambda());
+        case 1:
+            // swap last two
+            return new LinearInterpolation(original.getTrigramLambda(), original.getUnigramLambda(), original.getBigramLambda());
+        case 2:
+        default:
+            // swap first and last
+            return new LinearInterpolation(original.getUnigramLambda(), original.getBigramLambda(), original.getTrigramLambda());
+        }
+    }
+
+    @Override
+    void assertWordScorer(WordScorer wordScorer, SmoothingModel in) {
+        LinearInterpolation testModel = (LinearInterpolation) in;
+        LinearInterpoatingScorer testScorer = (LinearInterpoatingScorer) wordScorer;
+        assertThat(wordScorer, instanceOf(LinearInterpoatingScorer.class));
+        assertEquals(testModel.getTrigramLambda(), (testScorer).trigramLambda(), 1e-15);
+        assertEquals(testModel.getBigramLambda(), (testScorer).bigramLambda(), 1e-15);
+        assertEquals(testModel.getUnigramLambda(), (testScorer).unigramLambda(), 1e-15);
+    }
+}