### Question:
SpannerConnectionConfiguration { public GoogleCredentials getCredentials() { return this.credentials; } private  SpannerConnectionConfiguration(String url, GoogleCredentials credentials); private  SpannerConnectionConfiguration(
      String projectId,
      String instanceName,
      String databaseName,
      GoogleCredentials credentials); String getProjectId(); String getInstanceName(); String getDatabaseName(); String getFullyQualifiedDatabaseName(); GoogleCredentials getCredentials(); int getPartialResultSetFetchSize(); Duration getDdlOperationTimeout(); Duration getDdlOperationPollInterval(); int getThreadPoolSize(); @Override boolean equals(Object o); @Override int hashCode();  }### Answer:
@Test public void passingCustomGoogleCredentials() { SpannerConnectionConfiguration configuration = this.configurationBuilder .setProjectId("project") .setInstanceName("an-instance") .setDatabaseName("db") .build(); assertThat(configuration.getCredentials()).isSameAs(this.mockCredentials); }