Add SetNumInstancesCommand in Nomulus tool to adjust the number of instances

for a given service and version at runtime.

Note that this CL only supports the adjustment for a given service and version. I will add another functionality to let this command be able to detect all non-live versions automatically and apply the adjustment.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=221092001

javatests/google/registry/tools/SetNumInstancesCommandTest.java

@@ -0,0 +1,101 @@
+// Copyright 2018 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.tools;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.testing.JUnitBackports.assertThrows;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import com.beust.jcommander.ParameterException;
+import google.registry.testing.InjectRule;
+import google.registry.util.AppEngineServiceUtils;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.Mock;
+
+/** Unit tests for {@link SetNumInstancesCommand}. */
+public class SetNumInstancesCommandTest extends CommandTestCase<SetNumInstancesCommand> {
+
+  @Rule public final InjectRule inject = new InjectRule();
+
+  @Mock AppEngineServiceUtils appEngineServiceUtils;
+
+  @Before
+  public void before() {
+    command = new SetNumInstancesCommand();
+    command.appEngineServiceUtils = appEngineServiceUtils;
+  }
+
+  @Test
+  public void test_missingService_throwsException() {
+    ParameterException thrown =
+        assertThrows(
+            ParameterException.class, () -> runCommand("--version=version", "--numInstances=5"));
+    assertThat(thrown).hasMessageThat().contains("The following option is required: --service");
+  }
+
+  @Test
+  public void test_emptyService_throwsException() {
+    IllegalArgumentException thrown =
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> runCommand("--service=", "--version=version", "--numInstances=5"));
+    assertThat(thrown).hasMessageThat().contains("Service must be specified");
+  }
+
+  @Test
+  public void test_missingVersion_throwsException() {
+    ParameterException thrown =
+        assertThrows(
+            ParameterException.class, () -> runCommand("--service=service", "--numInstances=5"));
+    assertThat(thrown).hasMessageThat().contains("The following option is required: --version");
+  }
+
+  @Test
+  public void test_emptyVersion_throwsException() {
+    IllegalArgumentException thrown =
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> runCommand("--service=service", "--version=", "--numInstances=5"));
+    assertThat(thrown).hasMessageThat().contains("Version must be specified");
+  }
+
+  @Test
+  public void test_missingNumInstances_throwsException() {
+    ParameterException thrown =
+        assertThrows(
+            ParameterException.class, () -> runCommand("--service=service", "--version=version"));
+    assertThat(thrown)
+        .hasMessageThat()
+        .contains("The following option is required: --numInstances");
+  }
+
+  @Test
+  public void test_invalidNumInstances_throwsException() {
+    IllegalArgumentException thrown =
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> runCommand("--service=service", "--version=version", "--numInstances=-5"));
+    assertThat(thrown).hasMessageThat().contains("Number of instances must be greater than zero");
+  }
+
+  @Test
+  public void test_validParameters_succeeds() throws Exception {
+    runCommand("--service=service", "--version=version", "--numInstances=10");
+    verify(appEngineServiceUtils, times(1)).setNumInstances("service", "version", 10L);
+  }
+}