@Override
    @Nonnull
    public String format(@Nullable T argumentToFormat) {
        if ( argumentToFormat == null ) {
            return "null";
        }

        Class<?> clazz = argumentToFormat.getClass();
        if ( clazz.isArray() ) {
            DefaultFormatter<Object> defaultFormatter = new DefaultFormatter<Object>();
            return convertTArray(argumentToFormat)
                    .map(defaultFormatter::format)
                    .collect(Collectors.joining(", "));
        }
        return String.valueOf(argumentToFormat);
    }
A default formatter that merely use {@link String#valueOf(Object)},
except for arrays where {@link java.util.Arrays#deepToString(Object[])} is used.
jgiven-core/src/main/java/com/tngtech/jgiven/format/DefaultFormatter.java