Super simple start

src/main/test/net/minecraft/commands/CommandDispatcherTest.java

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+package net.minecraft.commands;
+
+import net.minecraft.commands.exceptions.UnknownCommandException;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class CommandDispatcherTest {
+    CommandDispatcher subject;
+    @Mock Runnable runnable;
+
+    @Before
+    public void setUp() throws Exception {
+        subject = new CommandDispatcher();
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testDuplicateCommand() throws Exception {
+        subject.createCommand("foo").executes(runnable).finish();
+        subject.createCommand("foo").executes(runnable).finish();
+    }
+
+    @Test
+    public void testCreateAndExecuteCommand() throws Exception {
+        subject.createCommand("foo").executes(runnable).finish();
+
+        subject.execute("foo");
+        Mockito.verify(runnable).run();
+    }
+
+    @Test(expected = UnknownCommandException.class)
+    public void testExecuteUnknownCommand() throws Exception {
+        subject.execute("foo");
+    }
+}

src/main/test/net/minecraft/commands/builder/CommandBuilderTest.java

@@ -0,0 +1,40 @@
+package net.minecraft.commands.builder;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Answers;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class CommandBuilderTest {
+    @Mock(answer = Answers.CALLS_REAL_METHODS) CommandBuilder builder;
+    @Mock Runnable commandExecutor;
+
+    @Before
+    public void setUp() throws Exception {
+        Mockito.doNothing().when(builder).onFinish();
+    }
+
+    @Test
+    public void testFinish() throws Exception {
+        builder.executes(commandExecutor);
+        builder.finish();
+
+        Mockito.verify(builder).onFinish();
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testFinishTwice() throws Exception {
+        builder.executes(commandExecutor);
+        builder.finish();
+        builder.finish();
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testFinishWithoutCommandExecutor() throws Exception {
+        builder.finish();
+    }
+}