Where did I go wrong in this code?
<p>A few of my classes aren't passing automated tests. Unfortunately, said tests do not provide any useful information about why they failed. Here is my code for a couple of the classes.  I'd really appreciate it if you could tell me where I went wrong. The comments should explain what each method is supposed to do.</p>

<pre><code>public class CellPhone {
    protected String ownerName;

        public CellPhone(String owner) {
           ownerName = owner;


        }

    public String receiveCall(CellPhone sender) {
        // returns a String of the form:
        // owner's name " is receiving a call from " sender's name
        String receivingCall = ownerName + " is receiving a call from " + sender;

        return receivingCall;
    }

    public String call(CellPhone receiver) {
        // returns a String by using the receiver to invoke receiveCall
        // while passing in the current phone
        String invokingReceiveCall = receiver.receiveCall(receiver);

        return invokingReceiveCall;

    }
}
</code></pre>

<hr>

<pre><code>public class TextMessagingPhone extends CellPhone {
    private int availMessages;

    public TextMessagingPhone(String owner, int messageLimit) {
        // invokes the superclass constructor
        super(owner);
        // sets the new instance variable
        availMessages = messageLimit;
    }

    public TextMessagingPhone(String owner) {
        // invokes the other constructor of this class with 15 as the message limit
        this(owner, 15);
    }

    public String receiveText(TextMessagingPhone sender, String message) {
        // decreases the number of messages available to send
        availMessages--;

        // returns a String of the form:
        // owner's name " has received TEXT from " sender's name ":" message
        String receivedText = ownerName + " has received TEXT from " + sender + ":" + message;

        return receivedText;
    }

    public String sendText(TextMessagingPhone receiver, String message) {
        // decreases the number of messages available to send
        availMessages--;

        // returns a String by using the receiver to invoke receiveText
        // while passing in the current phone and the message
        String invokingReceiveText = receiver.receiveText(receiver, message);

        return invokingReceiveText;
    }
}
</code></pre>
