### Question:
GcpComputePlatform extends Platform implements SshBasedExperiment<GcpComputeInstanceContainer> { public String stopInstance (GcpComputeInstanceContainer container) { log.info("Stopping instance {}", v(DATADOG_CONTAINER_KEY, container)); ProjectZoneInstanceName instance = getProjectZoneInstanceNameOfContainer(container, getProjectName()); return getInstanceClient().stopInstance(instance).getSelfLink(); }  void setRoutableCIDRBlocks(Collection<String> routableCIDRBlocks); @Override ApiStatus getApiStatus(); @Override PlatformLevel getPlatformLevel(); @Override PlatformHealth getPlatformHealth(); Collection<Items> getIncludeFilter(); void setIncludeFilter(Map<String, String> includeFilter); Collection<Items> getExcludeFilter(); void setExcludeFilter(Map<String, String> excludeFilter); @Override boolean isContainerRecycled(Container container); String stopInstance(GcpComputeInstanceContainer container); ContainerHealth isContainerRunning(GcpComputeInstanceContainer gcpComputeInstanceContainer); String simulateMaintenance(GcpComputeInstanceContainer container); String setTags(GcpComputeInstanceContainer container, List<String> tags); String setTagsSafe(GcpComputeInstanceContainer container, List<String> newTags, String oldFingerprint); boolean isContainerGroupAtCapacity(GcpComputeInstanceContainer container); boolean checkTags(GcpComputeInstanceContainer container, List<String> expectedTags); void startInstance(GcpComputeInstanceContainer container); String restartContainer(GcpComputeInstanceContainer container); String getBestEndpoint(String privateIPAddress, String publicIPAddress); boolean isAddressRoutable(String privateIPAddress); String getLatestInstanceId(String instanceName, String zone); Fingerprint<List<String>> getFirewallTags(GcpComputeInstanceContainer container); void setProjectId(String projectId); @Override String getEndpoint(GcpComputeInstanceContainer container); @Override SSHCredentials getSshCredentials(GcpComputeInstanceContainer container); @Override String getRunningDirectory(); @Override void recycleContainer(GcpComputeInstanceContainer container); String recreateInstanceInInstanceGroup(GcpComputeInstanceContainer container); boolean isOperationComplete(String operationId);  }### Answer:
@Test public void stopInstance () { String zone = "my-zone"; String uniqueIdentifier = "12345678901234567890"; GcpComputeInstanceContainer container = GcpComputeInstanceContainer.builder() .withUniqueIdentifier(uniqueIdentifier) .withZone(zone) .build(); ProjectZoneInstanceName instanceName = GcpComputePlatform.getProjectZoneInstanceNameOfContainer(container, projectName); Operation operation = Operation.newBuilder().setSelfLink("my-operation").build(); doReturn(operation).when(instanceClient).stopInstance(instanceName); assertEquals("my-operation", gcpComputePlatform.stopInstance(container)); }