test: Improve code coverage for Acl (#490)

* test: Improve code coverage for Acl
In Acl there's still untested class particularly the IamMember.
Also we can still improve the coverage by improving test for Group.

* docs(sample: Fix flaky test for AddEmptyColumnIT
Since nearly every table is using env var,
there's a possibility of concurrency problem in the test.

google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/AclTest.java

@@ -23,6 +23,7 @@
 import com.google.cloud.bigquery.Acl.Entity;
 import com.google.cloud.bigquery.Acl.Entity.Type;
 import com.google.cloud.bigquery.Acl.Group;
+import com.google.cloud.bigquery.Acl.IamMember;
 import com.google.cloud.bigquery.Acl.Role;
 import com.google.cloud.bigquery.Acl.User;
 import com.google.cloud.bigquery.Acl.View;
@@ -52,12 +53,20 @@ public void testGroupEntity() {
   public void testSpecialGroupEntity() {
     Group entity = Group.ofAllAuthenticatedUsers();
     assertEquals("allAuthenticatedUsers", entity.getIdentifier());
+    Dataset.Access pb = entity.toPb();
+    assertEquals(entity, Entity.fromPb(pb));
     entity = Group.ofProjectWriters();
     assertEquals("projectWriters", entity.getIdentifier());
+    pb = entity.toPb();
+    assertEquals(entity, Entity.fromPb(pb));
     entity = Group.ofProjectReaders();
     assertEquals("projectReaders", entity.getIdentifier());
+    pb = entity.toPb();
+    assertEquals(entity, Entity.fromPb(pb));
     entity = Group.ofProjectOwners();
     assertEquals("projectOwners", entity.getIdentifier());
+    pb = entity.toPb();
+    assertEquals(entity, Entity.fromPb(pb));
   }
 
   @Test
@@ -79,6 +88,14 @@ public void testViewEntity() {
     assertEquals(entity, Entity.fromPb(pb));
   }
 
+  @Test
+  public void testIamMemberEntity() {
+    IamMember entity = new IamMember("member1");
+    assertEquals("member1", entity.getIamMember());
+    Dataset.Access pb = entity.toPb();
+    assertEquals(entity, Entity.fromPb(pb));
+  }
+
   @Test
   public void testOf() {
     Acl acl = Acl.of(Group.ofAllAuthenticatedUsers(), Role.READER);

samples/snippets/src/test/java/com/example/bigquery/AddEmptyColumnIT.java

@@ -22,6 +22,10 @@
 import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
 import java.util.UUID;
+
+import com.google.cloud.bigquery.Field;
+import com.google.cloud.bigquery.LegacySQLTypeName;
+import com.google.cloud.bigquery.Schema;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
@@ -32,18 +36,16 @@ public class AddEmptyColumnIT {
   private PrintStream out;
 
   private static final String BIGQUERY_DATASET_NAME = System.getenv("BIGQUERY_DATASET_NAME");
-  private static final String BIGQUERY_TEST_TABLE = System.getenv("BIGQUERY_TEST_TABLE");
 
   private static void requireEnvVar(String varName) {
-    assertNotNull(
+    assertNotNull (
         "Environment variable " + varName + " is required to perform these tests.",
         System.getenv(varName));
   }
 
   @BeforeClass
   public static void checkRequirements() {
     requireEnvVar("BIGQUERY_DATASET_NAME");
-    requireEnvVar("BIGQUERY_TEST_TABLE");
   }
 
   @Before
@@ -60,8 +62,17 @@ public void tearDown() {
 
   @Test
   public void addEmptyColumn() {
+    String tableName = "AddEmptyColumnTestTable_" + UUID.randomUUID().toString().replace('-', '_');
+    Schema schema =
+            Schema.of(
+                    Field.of("booleanField", LegacySQLTypeName.BOOLEAN),
+                    Field.of("numericField", LegacySQLTypeName.NUMERIC));
+
+    // Create table in dataset for testing
+    CreateTable.createTable(BIGQUERY_DATASET_NAME, tableName, schema);
+
     String randomColumnName = "new_" + UUID.randomUUID().toString().replace('-', '_');
-    AddEmptyColumn.addEmptyColumn(randomColumnName, BIGQUERY_DATASET_NAME, BIGQUERY_TEST_TABLE);
+    AddEmptyColumn.addEmptyColumn(randomColumnName, BIGQUERY_DATASET_NAME, tableName);
     assertThat(bout.toString()).contains("Empty column successfully added to table");
   }
 }