Add unit test for validity processing

When a command is invalid, it is supposed to be flagged as such, with
problems recorded. There was a manual test for this in
scijava-plugins-commands called InvalidCommandDemo, which was a silly
place for such a thing. Much, much better to have a unit test here that
verifies this feature is working as expected.

This code was migrated and adapted from:
https://github.com/scijava/scijava-plugins-commands/blob/scijava-plugins-commands-0.1.8/src/main/java/org/scijava/plugins/commands/debug/InvalidCommandDemo.java

Author: ctrueden

src/test/java/org/scijava/command/InvalidCommandTest.java

@@ -0,0 +1,144 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2015 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.command;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.scijava.Context;
+import org.scijava.ItemIO;
+import org.scijava.ValidityProblem;
+import org.scijava.plugin.Parameter;
+import org.scijava.plugin.Plugin;
+
+/**
+ * Test commands for verifying that invalid module parameters are dealt with
+ * using proper error handling.
+ * 
+ * @author Curtis Rueden
+ */
+public class InvalidCommandTest {
+
+	private CommandService commandService;
+
+	@Before
+	public void setUp() {
+		Context ctx = new Context(CommandService.class);
+		commandService = ctx.getService(CommandService.class);
+	}
+
+	@Test
+	public void testValid() {
+		final CommandInfo info = commandService.getCommand(ValidCommand.class);
+		assertNotNull(info);
+		assertTrue(info.isValid());
+
+		final List<ValidityProblem> problems = info.getProblems();
+		assertNotNull(problems);
+		assertEquals(0, problems.size());
+	}
+
+	@Test
+	public void testInvalid() {
+		final CommandInfo info = commandService.getCommand(InvalidCommand.class);
+		assertNotNull(info);
+		assertFalse(info.isValid());
+
+		final List<ValidityProblem> problems = info.getProblems();
+		assertNotNull(problems);
+		assertEquals(2, problems.size());
+
+		final String p0 = problems.get(0).getMessage();
+		assertEquals("Invalid duplicate parameter: private int "
+			+ "org.scijava.command.InvalidCommandTest$InvalidCommand.x", p0);
+
+		final String p1 = problems.get(1).getMessage();
+		assertEquals("Invalid final parameter: private final float "
+			+ "org.scijava.command.InvalidCommandTest$InvalidCommand.y", p1);
+	}
+
+	// -- Helper classes --
+
+	/** A perfectly valid command! */
+	@Plugin(type = Command.class)
+	public static class ValidCommand implements Command {
+
+		@Parameter
+		private double x;
+
+		@Parameter(type = ItemIO.OUTPUT)
+		private String validOutput;
+
+		@Override
+		public void run() {
+			validOutput = "ValidCommand: success!";
+		}
+
+	}
+
+	/** A very much invalid command, for multiple reasons, explained below. */
+	@Plugin(type = Command.class)
+	public static abstract class InvalidCommand extends ValidCommand {
+
+		/**
+		 * This parameter is invalid because it shadows a private parameter of a
+		 * superclass. Such parameters violate the principle of parameter names as
+		 * unique keys.
+		 */
+		@Parameter
+		private int x;
+
+		/**
+		 * This parameter is invalid because it is declared {@code final} without
+		 * being {@link org.scijava.ItemVisibility#MESSAGE} visibility. Java does
+		 * not allow such parameter values to be set via reflection.
+		 */
+		@Parameter
+		private final float y = 0;
+
+		@Parameter(type = ItemIO.OUTPUT)
+		private String invalidOutput;
+
+		@Override
+		public void run() {
+			invalidOutput = "InvalidCommand: FAILURE";
+		}
+
+	}
+
+}