public void testInvalidFunctionEntryPoint() {

		// First thing we need to do is close the function graph window.  It's opened on
		// startup by default in this test suite but we want it closed until we clear the
		// function code bytes.
		this.getFunctionGraphController().getProvider().closeComponent();

		// Set up some additional plugins we need.
		try {
			tool.addPlugin(CodeBrowserPlugin.class.getName());
			tool.addPlugin(ClearPlugin.class.getName());
		}
		catch (PluginException e) {
			e.printStackTrace();
			return;
		}
		FunctionGraphPlugin fgp = getPlugin(tool, FunctionGraphPlugin.class);
		ClearPlugin cp = getPlugin(tool, ClearPlugin.class);
		CodeBrowserPlugin cb = env.getPlugin(CodeBrowserPlugin.class);

		// Clear the entry point instruction.
		DockingActionIf clearAction;
		clearAction = getAction(cp, "Clear Code Bytes");
		cb.goToField(program.getAddressFactory().getAddress("01002cf5"), "Address", 0, 0);
		final ActionContext context = cb.getProvider().getActionContext(null);
		runSwing(() -> clearAction.actionPerformed(context));
		waitForBusyTool(tool);

		// Open the window; the tool will try to generate a new graph but should fail and generate
		// an error message.
		DockingActionIf openGraphAction;
		openGraphAction = getAction(fgp, "Display Function Graph");
		runSwing(() -> openGraphAction.actionPerformed(context));
		waitForBusyTool(tool);

		// Assert that the graph has generated the correct error message and stored it in
		// the function graph data.
		FGController controller = getFunctionGraphController();
		FGData data = controller.getFunctionGraphData();
		assertTrue(data.getMessage().contains("No instruction at function entry point"));
	}
Tests that the app will recognize the case where the entry point to a function is invalid,
and generate the appropriate error message when trying to create a function graph.

Step 1: Make sure the function graph window is closed.
Step 2: Clear the entry point bytes
Step 3: Open the function graph window to generate the graph again.
Step 4: Check the error message.
Ghidra/Features/FunctionGraph/src/test.slow/java/ghidra/app/plugin/core/functiongraph/FunctionGraphGroupVertices1Test.java