SWTBot testing using JUnit on eclipse

I am newer to SWTBot testing. I encounter the following problem when I run the test cases on JUnit.

org.eclipse.swtbot.swt.finder.exceptions.WidgetNotFoundException: Could not find widget. at org.eclipse.swtbot.swt.finder.SWTBotFactory.waitUntilWidgetAppears(SWTBotFactory.java:348) at org.eclipse.swtbot.swt.finder.SWTBotFactory.widget(SWTBotFactory.java:308) at org.eclipse.swtbot.swt.finder.SWTBot.tree(SWTBot.java:1110) at org.eclipse.swtbot.swt.finder.SWTBot.tree(SWTBot.java:1099) at com.project.traceability.GUI.New.HomeGUITestCases.testNameInput(HomeGUITestCases.java:38) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) at org.junit.runners.ParentRunner.run(ParentRunner.java:309) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192) Caused by: org.eclipse.swtbot.swt.finder.widgets.TimeoutException: Timeout after: 5000 ms.: Could not find widget matching: (of type 'Tree') at org.eclipse.swtbot.swt.finder.SWTBotFactory.waitUntil(SWTBotFactory.java:398) at org.eclipse.swtbot.swt.finder.SWTBotFactory.waitUntil(SWTBotFactory.java:372) at org.eclipse.swtbot.swt.finder.SWTBotFactory.waitUntil(SWTBotFactory.java:360) at org.eclipse.swtbot.swt.finder.SWTBotFactory.waitUntilWidgetAppears(SWTBotFactory.java:346) ... 27 more