docs(sample): add IT for WriteToDefaultStream (#1158)

Fixes #1156

Author: stephaniewang526

samples/snippets/src/test/java/com/example/bigquerystorage/WriteToDefaultStreamIT.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2021 Google LLC
+ *
+ * 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.
+ */
+
+package com.example.bigquerystorage;
+
+import static com.google.common.truth.Truth.assertThat;
+import static junit.framework.TestCase.assertNotNull;
+
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQuery.DatasetDeleteOption;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.DatasetId;
+import com.google.cloud.bigquery.DatasetInfo;
+import com.google.cloud.bigquery.Field;
+import com.google.cloud.bigquery.Schema;
+import com.google.cloud.bigquery.StandardSQLTypeName;
+import com.google.cloud.bigquery.StandardTableDefinition;
+import com.google.cloud.bigquery.TableId;
+import com.google.cloud.bigquery.TableInfo;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.UUID;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class WriteToDefaultStreamIT {
+
+  private static final String GOOGLE_CLOUD_PROJECT = System.getenv("GOOGLE_CLOUD_PROJECT");
+
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+  private BigQuery bigquery;
+  private String datasetName;
+  private String tableName;
+
+  private static void requireEnvVar(String varName) {
+    assertNotNull(
+        "Environment variable " + varName + " is required to perform these tests.",
+        System.getenv(varName));
+  }
+
+  @BeforeClass
+  public static void checkRequirements() {
+    requireEnvVar("GOOGLE_CLOUD_PROJECT");
+  }
+
+  @Before
+  public void setUp() {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+
+    bigquery = BigQueryOptions.getDefaultInstance().getService();
+
+    // Create a new dataset and table for each test.
+    datasetName = "WRITE_STREAM_TEST" + UUID.randomUUID().toString().substring(0, 8);
+    tableName = "DEFAULT_STREAM_TEST" + UUID.randomUUID().toString().substring(0, 8);
+    Schema schema = Schema.of(Field.of("col1", StandardSQLTypeName.STRING));
+    bigquery.create(DatasetInfo.newBuilder(datasetName).build());
+    TableInfo tableInfo =
+        TableInfo.newBuilder(TableId.of(datasetName, tableName), StandardTableDefinition.of(schema))
+            .build();
+    bigquery.create(tableInfo);
+  }
+
+  @After
+  public void tearDown() {
+    bigquery.delete(
+        DatasetId.of(GOOGLE_CLOUD_PROJECT, datasetName), DatasetDeleteOption.deleteContents());
+    System.setOut(null);
+  }
+
+  @Test
+  public void testWriteToDefaultStream() throws Exception {
+    WriteToDefaultStream.writeToDefaultStream(GOOGLE_CLOUD_PROJECT, datasetName, tableName);
+    assertThat(bout.toString()).contains("Appended records successfully.");
+  }
+}