MutaFix run: boltons-003

tests/test_ioutils.py::TestSpooledStringIO::test_codepoints_all_enc
tests/test_ioutils.py::TestSpooledStringIO::test_truncate_noargs_norollover
tests/test_ioutils.py::TestSpooledStringIO::test_truncate_noargs_rollover
tests/test_ioutils.py::TestSpooledStringIO::test_truncate_with_args_norollover
tests/test_ioutils.py::TestSpooledStringIO::test_truncate_with_args_rollover

E   AssertionError: '———' != '——'
E   - ———
E   ? -
E   + ——
E   AssertionError: 'a☃bc' != 'bc'
E   - a☃bc
E   ? --
E   + bc
E   AssertionError: 'a☃bc' != 'bc'
E   - a☃bc
E   ? --
E   + bc
E   AssertionError: 'a☃bc' != 'bc'
E   - a☃bc
E   ? --

E   AssertionError: '' != 'Remember k'
E   + Remember k

1. boltons/ioutils.py::SpooledStringIO.read call depth 1 · Ochiai 0.48 (failing 7, passing 23)
2. boltons/ioutils.py::SpooledStringIO.rollover call depth 2 · Ochiai 0.48 (failing 4, passing 6)
3. boltons/ioutils.py::SpooledStringIO._rolled call depth 2 · Ochiai 0.48 (failing 4, passing 6)
4. boltons/ioutils.py::SpooledStringIO.seek call depth 1 · Ochiai 0.47 (failing 7, passing 24)
5. boltons/ioutils.py::SpooledStringIO._traverse_codepoints call depth 2 · Ochiai 0.47 (failing 7, passing 24)
6. boltons/ioutils.py::SpooledStringIO.write call depth 1 · Ochiai 0.43 (failing 7, passing 30)
7. boltons/ioutils.py::SpooledStringIO.tell call depth 2 · Ochiai 0.42 (failing 7, passing 33)
8. boltons/ioutils.py::SpooledIOBase.truncate call depth - · Ochiai 0.39 (failing 4, passing 11)
9. boltons/ioutils.py::SpooledStringIO.buffer call depth 2 · Ochiai 0.39 (failing 7, passing 40)
10. boltons/ioutils.py::SpooledStringIO.__init__ call depth - · Ochiai 0.39 (failing 7, passing 40)
11. boltons/ioutils.py::SpooledIOBase._checkClosed call depth 2 · Ochiai 0.31 (failing 7, passing 67)
12. boltons/ioutils.py::SpooledIOBase.closed call depth 2 · Ochiai 0.30 (failing 7, passing 69)
13. boltons/ioutils.py::SpooledIOBase.getvalue call depth 3 · Ochiai 0.30 (failing 4, passing 22)
14. boltons/ioutils.py::SpooledIOBase.__init__ call depth - · Ochiai 0.29 (failing 7, passing 77)
15. boltons/ioutils.py::SpooledIOBase._file call depth - · Ochiai 0.29 (failing 2, passing 5)
16. boltons/ioutils.py::SpooledIOBase.__exit__ call depth - · Ochiai 0.29 (failing 2, passing 5)
17. boltons/ioutils.py::SpooledIOBase.__enter__ call depth - · Ochiai 0.25 (failing 2, passing 7)
18. boltons/ioutils.py::SpooledIOBase.close call depth 3 · Ochiai 0.13 (failing 3, passing 77)
19. boltons/ioutils.py::SpooledIOBase.__del__ call depth - · Ochiai 0.13 (failing 3, passing 77)
20. boltons/ioutils.py::SpooledStringIO.len call depth 1 · Ochiai 0.00 (failing 0, passing 4)

We need to fix the UnboundLocalError: 'ret' might be referenced before assignment in the case where we go into the branch `if current_position + READ_CHUNK_SIZE > dest:` and do `self.read(...)`, but we don't assign to `ret`. Then later we check `if not ret:` which causes the error.

We need to ensure `ret` is defined in all branches, or restructure to avoid using `ret` when not needed.

Alternatively, we can move the check for empty read inside the else branch? Actually, we need to break if read returns empty regardless of which branch we took.

Better approach: after each read, capture the result and check if it's empty.

Let's rewrite:

while current_position != dest:
    if current_position + READ_CHUNK_SIZE > dest:
        chunk = self.read(dest - current_position)
        current_position += len(chunk)   # Actually we should advance by the number of codepoints read? But read returns string, and we are counting codepoints? However, note that self.read(n) reads n codepoints? Actually, the read method of SpooledStringIO reads n characters? Let's look at the read method: it calls self.buffer.reader.read(n, n) and returns ret. The buffer is an EncodedFile with utf-8 encoding, so reading n characters? Actually, the EncodedFile's read method: it reads n characters from the underlying binary stream and decodes them. So self.read(n) returns up to n characters (codepoints). So we can advance current_position by the length of the returned string (in characters). However, note that 

We need to fix the function. The issue is that the condition `if not (current_position == dest):` means: if they are NOT equal, then break. So it breaks when they are not equal, i.e., almost always at the start. We want to continue looping until they are equal. So we should break when they ARE equal? Actually we want to stop when we have reached dest. So we want to loop while current_position != dest. And inside, we do the read and increment.

But note: the comment says "# By chance we've landed on the right position, break". That suggests that if we are already at dest, we break. But the condition is reversed.

Let's rewrite:

We want to traverse n codepoints from current_position. We'll set dest = current_position + n.

While current_position < dest (since we are moving forward), we read chunks.

However, the function also handles negative n? Probably not, because n is the number of codepoints to move to the right. In the seek method, n can be negative? Let's see: in seek, for SEEK_CUR, if pos < 0, they call self.seek(destination) recursively. For SEEK_END, dest_position = self.len - pos, which could be less than current? Actually they call _traverse_codepoints(0, dest_position). So n is non-negative? Not necessarily: if pos is negative in SEEK_END? But they check for negative seek position earlier? In SEEK_END, they don't check if dest_position is negative? They compute dest_position = self.len - pos. If pos is positive, dest_position < self.len. If pos is negative, dest_p