This error is coming as system is not able to understand `Test123` while parsing into date.

The format of the String depends on the local date format, like `mm/dd/yyyy`. If the parameter is not of this format, `date.parse` will throw error.

E.g.:

<!-- language: lang-java -->

    r.Plan_Date__c = date.parse('12/27/2015');

You can also use `date.valueOf(strDate)` to parse string of format `yyyy-MM-dd HH:mm:ss` in the local time zone.

Please use [this link][1] to read about more date properties.

  [1]: https://developer.salesforce.com/docs/atlas.en-us.198.0.apexcode.meta/apexcode/apex_methods_system_date.htm#apex_System_Date_parse