# def validate_account_number_format(account_string):
# Return false if invalid, true if valid
# ...

# Import the code to be tested
import validators

# Import the test framework (this is a hypothetical module)
import test_framework

# This is a generalized example, not specific to a test framework


class Test_TestAccountValidator(test_framework.TestBaseClass):
    def test_validator_valid_string():
        # The exact assertion call depends on the framework as well
        assert(validate_account_number_format("1234567890"), true)

    # ...

    def test_validator_blank_string():
        # The exact assertion call depends on the framework as well
        assert(validate_account_number_format(""), false)

    # ...

    def test_validator_sql_injection():
        # The exact assertion call depends on the framework as well
        assert(validate_account_number_format("drop database master"), false)

    # ... tests for all other cases
