The -nottycopy option makes the PosixSysTerminal to have a 0,0 size. So any cursor movement (completion, delete char, add char) gets you / by zero

/usr/bin/expect
spawn -nottycopy java -jar examples/target/aesh-examples-1.10.jar
interact
<type a character>
[aesh@rules]$ Exception in thread "main" java.lang.ArithmeticException: / by zero
at org.aesh.readline.Buffer.printInsertedData(Buffer.java:586)
at org.aesh.readline.Buffer.insert(Buffer.java:235)
at org.aesh.readline.AeshConsoleBuffer.writeChar(AeshConsoleBuffer.java:130)
at org.aesh.readline.Readline$AeshInputProcessor.parse(Readline.java:252)
at org.aesh.readline.Readline$AeshInputProcessor.access$100(Readline.java:174)
at org.aesh.readline.Readline.readInput(Readline.java:95)
at org.aesh.readline.Readline.access$1000(Readline.java:57)
at org.aesh.readline.Readline$AeshInputProcessor.lambda$start$1(Readline.java:324)
at org.aesh.terminal.EventDecoder.accept(EventDecoder.java:118)
at org.aesh.terminal.EventDecoder.accept(EventDecoder.java:31)
at org.aesh.io.Decoder.write(Decoder.java:133)
at org.aesh.readline.tty.terminal.TerminalConnection.openBlocking(TerminalConnection.java:216)
at org.aesh.readline.tty.terminal.TerminalConnection.openBlocking(TerminalConnection.java:203)
at org.aesh.readline.ReadlineConsole.accept(ReadlineConsole.java:232)
at org.aesh.readline.ReadlineConsole.accept(ReadlineConsole.java:86)
at org.aesh.readline.tty.terminal.TerminalConnection.init(TerminalConnection.java:153)
at org.aesh.readline.tty.terminal.TerminalConnection.<init>(TerminalConnection.java:86)
at org.aesh.readline.tty.terminal.TerminalConnection.<init>(TerminalConnection.java:96)
at org.aesh.readline.ReadlineConsole.start(ReadlineConsole.java:180)
at examples.Example.main(Example.java:164)