Yes, the __toString is really just a magic method and a simple casting should work just as well. In your example it could be something like: (string) $value. String concatenation also works. Have you considered something like the following?
public function i_set_the_field_to($name, PyStringNode $content) {
return array(new Given('I set the field "'. $name. '" to "'. $content. '"'));
}
With $value as PyString, try $value->__toString().
I don't know how to make this work with the conditions you use so can't offer much help with that. If you don't manage to make it work and/or looking for an alternate approach, you may want to consider the solution described in Personalized access to course activities/resources. It requires 2.8.5 and an addon, but it allows you to manage everyone's access to the various activities from one dashboard. hth
This assumes that you have a set number of projects, one per student, which does not allow students to determine for themselves what it is they want to learn about.
The assumption is not necessary.
As I understand the OP requirement, it rather allows student to pick their preferred project. It is only reasonable that the instructor limits the scope by a predefined list of suitable projects to work on in the context.
The solution I've referred the OP to is rather open ended. You can have more projects than students, so that the late birds can still have options. You can have less projects than students in which case some projects will be worked on by more than one student. You can also set it up such that the intructor determines the study plan (that is course activities to complete) for students (all or some) or the students determine their on study plan. See my related post in this thread: https://moodle.org/mod/forum/discuss.php?d=311241.
See if the solution described in the thread https://moodle.org/mod/forum/discuss.php?d=310898 can work for you. The docs describe an application where the instructor assigns the personal study plan to participants by adding the plan entries on behalf of participants, but you can simplify that application to allow participants to create their own plan by allowing them to add their own entries. If you set the course activities completion criteria, the course completion report will give you the record of planned vs. actual. hth