Add ShellFactory get shell test

Author: cosmo0920

build.gradle

@@ -19,6 +19,7 @@ dependencies {
     provided "org.embulk:embulk-core:0.7.0"
     // compile "YOUR_JAR_DEPENDENCY_GROUP:YOUR_JAR_DEPENDENCY_MODULE:YOUR_JAR_DEPENDENCY_VERSION"
     testCompile "junit:junit:4.+"
+    testCompile 'org.embulk:embulk-core:0.7.+:tests'
 }
 
 task classpath(type: Copy, dependsOn: ["jar"]) {

src/main/java/org/embulk/output/CommandFileOutputPlugin.java

@@ -5,6 +5,8 @@
 import java.io.OutputStream;
 import java.io.FilterOutputStream;
 import java.io.IOException;
+
+import com.google.common.annotations.VisibleForTesting;
 import org.slf4j.Logger;
 import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
@@ -73,7 +75,8 @@ public TransactionalFileOutput open(TaskSource taskSource, final int taskIndex)
         return new PluginFileOutput(cmdline, taskIndex);
     }
 
-    private static class ShellFactory
+    @VisibleForTesting
+    static class ShellFactory
     {
         private List<String> shell;
 

src/test/java/org/embulk/output/TestCommandFileOutputPlugin.java

@@ -1,5 +1,39 @@
 package org.embulk.output;
 
+import com.google.common.collect.ImmutableList;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.embulk.EmbulkTestRuntime;
+import org.embulk.output.CommandFileOutputPlugin.ShellFactory;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
 public class TestCommandFileOutputPlugin
 {
+    @Rule
+    public EmbulkTestRuntime runtime = new EmbulkTestRuntime();
+
+    private ShellFactory shellFactory;
+
+    @Before
+    public void createResources()
+    {
+        shellFactory = new ShellFactory().build();
+    }
+
+    @Test
+    public void testShell() {
+        List<String> shell = shellFactory.get();
+        String osName = System.getProperty("os.name");
+        List<String> actualShellCmd;
+        if (osName.contains("Windows")) {
+            actualShellCmd = ImmutableList.of("PowerShell.exe", "-Command");
+        } else {
+            actualShellCmd = ImmutableList.of("sh", "-c");
+        }
+        assertEquals(actualShellCmd, shell);
+    }
 }