If an expected error is specified and that error occurs, mysqltest continues reading input.

If the command is successful or a different error occurs, mysqltest aborts.

If no expected error is specified, mysqltest aborts unless the command is successful. (It is implicit that you expect $mysql_errno to be 0.)

By default, mysqltest aborts for certain conditions:

A statement that fails when it should have succeeded. The following statement should succeed if table t exists;
```
SELECT * FROM t;
```
A statement that fails with an error different from that specified:
```
--error 1
SELECT * FROM no_such_table;
```
A statement that succeeds when an error was expected:
```
--error 1
SELECT 'a string';
```

You can disable the abort for errors of the first type by using the disable_abort_on_error command. In this case, when errors occur for statements that should succeed, mysqltest continues processing intput.

disable_abort_on_error does not cause mysqltest to ignore errors for the other two types, where you explicitly state which error you expect. This behavior is intentional. The rationale is that if you use the error command to specify an expected error, it is assumed that the test is sufficiently well characterized that only the specified error is accceptable.

If you do not use the error command, it is assumed that you might not know which error to expect or that it might be difficult to characterize all possible errors that could occur. In this case, disable_abort_on_error is useful for causing mysqltest — Program to Run Test Cases mysqltest to continue processing input. This can be helpful in the following circumstances:

During test case development, it is useful to process all input even if errors occur so that you can see all errors at once, such as those that occur due to typographical or syntax errors. Otherwise, you can see and fix only one scripting problem at a time.
Within a file that is included with a source command by several different test cases, errors might vary depending on the processing environment that is set up prior to the source command.
Tests that follow a given statement that can fail are independent of that statement and do not depend on its result.