Error Codes
When Mocha itself throws exception, the associated Error will have a code property.
Where applicable, consumers should check the code property instead of string-matching against the message property.
The following table describes these error codes:
| Code | Description |
| ----------------------------------------- | --------------------------------------------------------------------- |
| ERR_MOCHA_FATAL | an unrecoverable error occurred |
| ERR_MOCHA_FORBIDDEN_EXCLUSIVITY | .only() was used with --forbid-only |
| ERR_MOCHA_INSTANCE_ALREADY_DISPOSED | run() was called on a Mocha instance that has already been disposed |
| ERR_MOCHA_INSTANCE_ALREADY_RUNNING | run() was called on a Mocha instance that is already running |
| ERR_MOCHA_INVALID_ARG_TYPE | wrong type was passed for a given argument |
| ERR_MOCHA_INVALID_ARG_VALUE | invalid or unsupported value was passed for a given argument |
| ERR_MOCHA_INVALID_EXCEPTION | a falsy or otherwise underspecified exception was thrown |
| ERR_MOCHA_INVALID_INTERFACE | interface specified in options not found |
| ERR_MOCHA_INVALID_PLUGIN_DEFINITION | a plugin definition (e.g., mochaHooks) was invalid |
| ERR_MOCHA_INVALID_PLUGIN_IMPLEMENTATION | a user-supplied plugin implementation was invalid |
| ERR_MOCHA_INVALID_REPORTER | reporter specified in options not found |
| ERR_MOCHA_MULTIPLE_DONE | done() was called multiple times in a test or hook |
| ERR_MOCHA_NO_FILES_MATCH_PATTERN | test file(s) could not be found |
| ERR_MOCHA_TIMEOUT | a test or hook exceeded its allowed run time |
| ERR_MOCHA_UNPARSABLE_FILE | a configuration or test file could not be parsed |
| ERR_MOCHA_UNSUPPORTED | requested behavior, option, or parameter is unsupported |