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test/unit/stream_spec.js

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+/* Copyright 2017 Mozilla Foundation
+ *
+ * Licensed 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.
+ */
+
+import { Dict } from "../../src/core/primitives.js";
+import { PredictorStream } from "../../src/core/predictor_stream.js";
+import { Stream } from "../../src/core/stream.js";
+
+describe("stream", function () {
+  describe("PredictorStream", function () {
+    it("should decode simple predictor data", function () {
+      const dict = new Dict();
+      dict.set("Predictor", 12);
+      dict.set("Colors", 1);
+      dict.set("BitsPerComponent", 8);
+      dict.set("Columns", 2);
+
+      const input = new Stream(
+        new Uint8Array([2, 100, 3, 2, 1, 255, 2, 1, 255]),
+        0,
+        9,
+        dict
+      );
+      const predictor = new PredictorStream(input, /* length = */ 9, dict);
+      const result = predictor.getBytes(6);
+
+      expect(result).toEqual(new Uint8Array([100, 3, 101, 2, 102, 1]));
+    });
+  });
+});