add tests for the selector logic that keeps breaking

Four bugs that reached real runs are covered: a point value the parser could not read, the wrong row of the breakdown panel, a container that looks right but is empty, and a label that matches two different buttons.

Stdlib unittest with small fakes for the selenium calls the selectors make, so this adds no dependency and needs no browser. Run with python -m unittest discover -s tests.

tests/fakes.py

@@ -0,0 +1,41 @@
+"""Minimal stand-ins for the selenium objects the selectors read.
+
+Only what the selectors actually call is implemented: text, DOM attributes,
+visibility and find_element(s). Enough to drive the parsing and filtering
+without a browser, and small enough to stay readable.
+"""
+
+from selenium.common.exceptions import NoSuchElementException
+
+
+class FakeElement:
+	def __init__(self, text="", attributes=None, children=None, displayed=True):
+		self.text = text
+		self.attributes = attributes or {}
+		# {(by, selector): [FakeElement, ...]}
+		self.children = children or {}
+		self.displayed = displayed
+
+	def get_dom_attribute(self, name):
+		return self.attributes.get(name)
+
+	def is_displayed(self):
+		return self.displayed
+
+	def find_elements(self, by, selector):
+		return list(self.children.get((by, selector), []))
+
+	def find_element(self, by, selector):
+		found = self.find_elements(by, selector)
+
+		if not found:
+			raise NoSuchElementException(f"no element for {by} {selector!r}")
+
+		return found[0]
+
+
+class FakeDriver(FakeElement):
+	"""A driver behaves like an element for the lookups used here."""
+
+	def __init__(self, children=None):
+		super().__init__(children=children)