diff --git a/tests/test_retrying_core.py b/tests/test_retrying_core.py
new file mode 100644
index 00000000..df455012
--- /dev/null
+++ b/tests/test_retrying_core.py
@@ -0,0 +1,144 @@
+import pytest
+from tenacity import (
+    retry, Retrying,
+    stop_after_attempt, stop_after_delay,
+    wait_fixed, wait_exponential,
+    retry_if_exception_type, retry_if_result
+)
+
+def no_sleep(_seconds: float) -> None:
+    return
+
+def test_success_after_retries_on_exception():
+    calls = {"n": 0}
+
+    @retry(
+        stop=stop_after_attempt(3),
+        retry=retry_if_exception_type(ValueError),
+        wait=wait_fixed(0),
+        reraise=True,
+        sleep=no_sleep,
+    )
+    def flaky():
+        calls["n"] += 1
+        if calls["n"] < 3:
+            raise ValueError("temporary")
+        return "OK"
+
+    result = flaky()
+    assert result == "OK"
+    assert calls["n"] == 3
+
+def test_reraise_on_exhausted_attempts():
+    @retry(
+        stop=stop_after_attempt(2),
+        retry=retry_if_exception_type(RuntimeError),
+        wait=wait_fixed(0),
+        reraise=True,
+        sleep=no_sleep,
+    )
+    def always_fails():
+        raise RuntimeError("bad")
+
+    with pytest.raises(RuntimeError):
+        always_fails()
+
+def test_stop_after_delay_boundary():
+    attempts = {"n": 0}
+    r = Retrying(
+        stop=stop_after_delay(0.01),
+        wait=wait_fixed(0),
+        retry=retry_if_exception_type(ValueError),
+        reraise=False,
+        sleep=no_sleep,
+    )
+    def fn():
+        attempts["n"] += 1
+        raise ValueError("still failing")
+
+    with pytest.raises(ValueError):
+        r(fn)
+    assert attempts["n"] >= 1
+
+def test_retry_on_result_predicate():
+    results = iter([None, None, 42])
+
+    @retry(
+        stop=stop_after_attempt(5),
+        retry=retry_if_result(lambda x: x is None),
+        wait=wait_fixed(0),
+        reraise=True,
+        sleep=no_sleep,
+    )
+    def maybe_none():
+        return next(results)
+
+    value = maybe_none()
+    assert value == 42
+
+def test_before_after_callbacks_called_in_order():
+    events = []
+
+    def before_fn(retry_state):
+        events.append(("before", retry_state.attempt_number))
+
+    def after_fn(retry_state):
+        exc = retry_state.outcome.exception()
+        events.append(("after", retry_state.attempt_number, type(exc).__name__ if exc else None))
+
+    @retry(
+        stop=stop_after_attempt(3),
+        retry=retry_if_exception_type(KeyError),
+        wait=wait_fixed(0),
+        before=before_fn,
+        after=after_fn,
+        reraise=False,
+        sleep=no_sleep,
+    )
+    def will_fail_then_fail_then_succeed():
+        if len([e for e in events if e[0] == "after"]) < 2:
+            raise KeyError("nope")
+        return "done"
+
+    result = will_fail_then_fail_then_succeed()
+    assert result == "done"
+    assert events[0][0] == "before"
+    assert events[1][0] == "after"
+    assert events[1][2] == "KeyError"
+
+def test_wait_exponential_caps_sleep_without_jitter():
+    sleeps = []
+    def record_sleep(seconds):
+        sleeps.append(seconds)
+
+    @retry(
+        stop=stop_after_attempt(4),
+        retry=retry_if_exception_type(ValueError),
+        wait=wait_exponential(multiplier=1, min=1, max=4),
+        reraise=False,
+        sleep=record_sleep,
+    )
+    def always_fail():
+        raise ValueError("x")
+
+    with pytest.raises(ValueError):
+        always_fail()
+    assert sleeps[:3] == [1, 2, 4]
+
+def test_non_retryable_exception_bubbles_immediately():
+    calls = {"n": 0}
+
+    @retry(
+        stop=stop_after_attempt(5),
+        retry=retry_if_exception_type(ValueError),
+        wait=wait_fixed(0),
+        reraise=True,
+        sleep=no_sleep,
+    )
+    def raises_type_error():
+        calls["n"] += 1
+        raise TypeError("do not retry this")
+
+    with pytest.raises(TypeError):
+        raises_type_error()
+    assert calls["n"] == 1