New unittest discovery code doesn't discover all tests

Repro steps:

• Create a folder with a Python file and a tests folder
• Inside the tests folder add a test file test_something.py (name can be anything as long as it starts with test_) with the following content:

import unittest


class Testing(unittest.TestCase):
    def test_string(self):
        a = "some"
        b = "some"
        self.assertEqual(a, b)

    def test_boolean(self):
        a = True
        b = True
        print("this is a test")
        self.assertEqual(a, b)


class OtherTesting(unittest.TestCase):
    def test_equal_string(self):
        a = "some"
        b = "some"
        self.assertEqual(a, b)

    def test_equal_boolean(self):
        a = True
        b = True
        self.assertEqual(a, b)


class IntegerArithmeticTestCase(unittest.TestCase):
    def testAdd(self):  # test method names begin with 'test'
        self.assertEqual((1 + 2), 3)
        self.assertEqual(0 + 1, 1)

    def testMultiply(self):
        self.assertEqual((0 * 10), 0)
        self.assertEqual((5 * 8), 40)

• In your workspace settings, make sure that testing using unittest is enabled (look for the python.testing.unittestEnabled setting and tick the checkbox), and that the value of the python.testing.unittestArgs setting is as follows:

[
    "-v",
    "-s",
    "./tests",
    "-p",
    "test_*.py"
  ]

• Use the current discovery code, notice that the unit tests under the Testing, OtherTesting and `IntegerArithmeticTestCase are found
• Swap to the new discovery code, notice that not all of the tests are found

⚠️ It might have something to do with some of the test names being camelCase (testMultiply) while others are snake case (test_boolean). Both conventions should be supported anyway. Could also be that the current discovery algorithm stops at the first testing class.

[kimadeline]

That is for you to figure out and fix 🙂

[ksy7588]

fixed: https://github.com/microsoft/vscode-python/pull/19324