[SalesForce] Converting a field type from number to text

Yes, APEX, the language used to write triggers, supports find and replace. String types (which include rich-text fields) have a number of options, primarily String.replace() and String.replaceAll() (see the String methods for the full list). You also use Pattern and Matcher classes that can do more complex regex related activities (see the Pattern and Matcher docs).

Basic Example

trigger YourTrigger on Solution (before update) {   
  for(Solution s : trigger.new) {
    s.replaceAll('Hello World','Goodbye World');
  }
}

More Info

If you're looking to explore what other functionality is available, you'll want to have the APEX API Reference handy.

Usually, we don't throw exception from the testmethods, rather we catch the exception and put them in proper way through assert statement.

like this:

public class MyClass
{
    public String accountId {get;set;}

    public void myMethod()
    {
        if(accountId == null)
        {
            throw new exception ('Account Id is blank');
        }
    }

}

test class to handle exception

public static testmethod void  mytest()
{
    MyClass cls = new MyClass();

    cls.accountId = null;

    try
    {
        cls.myMethod();

    }
    catch (Exception ex)
    {
        if(ex.getMessage().contains('Account Id is blank')
        {
            System.assert(true);    
        }
        else
        {
            System.assert(false);
        }

    }

}

So, it boils down to option D, eliminating all other options as follows:

A) Throwing a customer exception in the unit test - This cannot be good option

B) Assert that a null value is accepted by the method - This is not a testing negative scenario

C) Asert that past dates are accepted by the method - This is positive test

D) Assert that future dates are rejected by the method - This is correct way for doing negative test.