[BEAM-143] [flink] add test for UnboundedSourceWrapper

The test ensures serialization and execution of the wrapper works as
expected.

runners/flink/runner/src/test/java/org/apache/beam/runners/flink/streaming/UnboundedSourceITCase.java

@@ -0,0 +1,203 @@
+/*
+ * 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.beam.runners.flink.streaming;
+
+import com.google.cloud.dataflow.sdk.Pipeline;
+import com.google.cloud.dataflow.sdk.coders.BigEndianIntegerCoder;
+import com.google.cloud.dataflow.sdk.coders.Coder;
+import com.google.cloud.dataflow.sdk.io.Read;
+import com.google.cloud.dataflow.sdk.io.TextIO;
+import com.google.cloud.dataflow.sdk.io.UnboundedSource;
+import com.google.cloud.dataflow.sdk.options.PipelineOptions;
+import com.google.cloud.dataflow.sdk.transforms.DoFn;
+import com.google.cloud.dataflow.sdk.transforms.ParDo;
+import com.google.cloud.dataflow.sdk.transforms.windowing.AfterPane;
+import com.google.cloud.dataflow.sdk.transforms.windowing.BoundedWindow;
+import com.google.cloud.dataflow.sdk.transforms.windowing.GlobalWindow;
+import com.google.cloud.dataflow.sdk.transforms.windowing.GlobalWindows;
+import com.google.cloud.dataflow.sdk.transforms.windowing.PaneInfo;
+import com.google.cloud.dataflow.sdk.transforms.windowing.Window;
+import com.google.cloud.dataflow.sdk.util.WindowedValue;
+import com.google.cloud.dataflow.sdk.values.PCollection;
+import com.google.common.base.Joiner;
+import org.apache.beam.runners.flink.FlinkTestPipeline;
+import org.apache.flink.streaming.util.StreamingProgramTestBase;
+import org.joda.time.Instant;
+import org.junit.internal.ArrayComparisonFailure;
+
+import javax.annotation.Nullable;
+import java.io.IOException;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+
+public class UnboundedSourceITCase extends StreamingProgramTestBase {
+
+  protected static String resultPath;
+
+  public UnboundedSourceITCase() {
+  }
+
+  static final String[] EXPECTED_RESULT = new String[]{
+      "1", "2", "3", "4", "5", "6", "7", "8", "9"};
+
+  @Override
+  protected void preSubmit() throws Exception {
+    resultPath = getTempDirPath("result");
+  }
+
+  @Override
+  protected void postSubmit() throws Exception {
+    compareResultsByLinesInMemory(Joiner.on('\n').join(EXPECTED_RESULT), resultPath);
+  }
+
+  @Override
+  protected void testProgram() throws Exception {
+    runProgram(resultPath);
+  }
+
+  private static void runProgram(String resultPath) {
+
+    Pipeline p = FlinkTestPipeline.createForStreaming();
+
+    PCollection<String> result = p
+        .apply(Read.from(new RangeReadSource(1, 10)))
+        .apply(Window.<Integer>into(new GlobalWindows())
+            .triggering(AfterPane.elementCountAtLeast(10))
+            .discardingFiredPanes())
+        .apply(ParDo.of(new DoFn<Integer, String>() {
+          @Override
+          public void processElement(ProcessContext c) throws Exception {
+            c.output(c.element().toString());
+          }
+        }));
+
+    result.apply(TextIO.Write.to(resultPath));
+
+    try {
+      p.run();
+    } catch(Exception e) {
+      assertEquals("The source terminates as expected.", e.getCause().getCause().getMessage());
+    }
+  }
+
+
+  private static class RangeReadSource extends UnboundedSource<Integer, UnboundedSource.CheckpointMark> {
+
+    final int from;
+    final int to;
+
+    RangeReadSource(int from, int to) {
+      this.from = from;
+      this.to = to;
+    }
+
+
+    @Override
+    public List<? extends UnboundedSource<Integer, CheckpointMark>> generateInitialSplits(
+        int desiredNumSplits, PipelineOptions options) throws Exception {
+      return null;
+    }
+
+    @Override
+    public UnboundedReader<Integer> createReader(PipelineOptions options, @Nullable CheckpointMark checkpointMark) {
+      return new RangeReadReader(options);
+    }
+
+    @Nullable
+    @Override
+    public Coder<CheckpointMark> getCheckpointMarkCoder() {
+      return null;
+    }
+
+    @Override
+    public void validate() {
+    }
+
+    @Override
+    public Coder<Integer> getDefaultOutputCoder() {
+      return BigEndianIntegerCoder.of();
+    }
+
+    private class RangeReadReader extends UnboundedReader<Integer> {
+
+      private int current;
+
+      public RangeReadReader(PipelineOptions options) {
+        assertNotNull(options);
+        current = from;
+      }
+
+      @Override
+      public boolean start() throws IOException {
+        return true;
+      }
+
+      @Override
+      public boolean advance() throws IOException {
+        current++;
+        if (current >= to) {
+          try {
+            compareResultsByLinesInMemory(Joiner.on('\n').join(EXPECTED_RESULT), resultPath);
+            throw new IOException("The source terminates as expected.");
+          } catch (IOException e) {
+            // pass on the exception to terminate the source
+            throw e;
+          } catch (Throwable t) {
+            // expected here from the file check
+          }
+        }
+        return current < to;
+      }
+
+      @Override
+      public Integer getCurrent() throws NoSuchElementException {
+        return current;
+      }
+
+      @Override
+      public Instant getCurrentTimestamp() throws NoSuchElementException {
+        return Instant.now();
+      }
+
+      @Override
+      public void close() throws IOException {
+      }
+
+      @Override
+      public Instant getWatermark() {
+        return Instant.now();
+      }
+
+      @Override
+      public CheckpointMark getCheckpointMark() {
+        return null;
+      }
+
+      @Override
+      public UnboundedSource<Integer, ?> getCurrentSource() {
+        return RangeReadSource.this;
+      }
+    }
+  }
+}
+
+