fix: catch null Firestore in system tests (#215)

Author: Brian Chen

google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITQueryWatchTest.java

@@ -39,6 +39,7 @@
 import com.google.common.base.Joiner;
 import com.google.common.base.Joiner.MapJoiner;
 import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
 import com.google.common.base.Predicate;
 import com.google.common.collect.FluentIterable;
 import com.google.common.collect.Range;
@@ -83,6 +84,9 @@ public void before() {
 
  @AfterClass
  public static void afterClass() throws Exception {
+ Preconditions.checkNotNull(
+ firestore,
+ "Error instantiating Firestore. Check that the service account credentials were properly set.");
  firestore.close();
  }
 

google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java

@@ -55,6 +55,7 @@
 import com.google.cloud.firestore.Transaction.Function;
 import com.google.cloud.firestore.WriteBatch;
 import com.google.cloud.firestore.WriteResult;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import java.util.ArrayList;
@@ -104,6 +105,9 @@ public void before() {
 
  @After
  public void after() throws Exception {
+ Preconditions.checkNotNull(
+ firestore,
+ "Error instantiating Firestore. Check that the service account credentials were properly set.");
  firestore.close();
  }