Add integration test module

This is for higher level tests, perhaps relying on 3rd party libraries
(dev only dependencies.)  This first set uses the `requests` module
to test some idiomatic patterns using the `runtime` wait generator.

pyproject.toml

@@ -35,6 +35,8 @@ pytest = "^6.2.2"
 pytest-cov = "^2.11.1"
 pytest-asyncio = "^0.14.0"
 mypy = "^0.812"
+requests = "^2.26.0"
+responses = "^0.13.4"
 
 [build-system]
 requires = ["poetry-core>=1.0.0"]

tests/test_integration.py

@@ -0,0 +1,78 @@
+"""Integration tests
+
+Higher-level tests integrating with 3rd party modules using iodiomatic
+backoff patterns.
+"""
+
+import backoff
+
+
+import requests
+from requests import HTTPError
+import responses
+
+
+@responses.activate
+def test_on_predicate_runtime(monkeypatch):
+
+    log = []
+
+    def sleep(seconds):
+        log.append(seconds)
+
+    monkeypatch.setattr("time.sleep", sleep)
+
+    url = "http://example.com"
+
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "1"})
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "3"})
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "7"})
+    responses.add(responses.GET, url, status=200)
+
+    @backoff.on_predicate(
+        backoff.runtime,
+        predicate=lambda r: r.status_code == 429,
+        value=lambda r: int(r.headers.get("Retry-After")),
+        jitter=None,
+    )
+    def get_url():
+        return requests.get(url)
+
+    resp = get_url()
+    assert resp.status_code == 200
+
+    assert log == [1, 3, 7]
+
+
+@responses.activate
+def test_on_exception_runtime(monkeypatch):
+
+    log = []
+
+    def sleep(seconds):
+        log.append(seconds)
+
+    monkeypatch.setattr("time.sleep", sleep)
+
+    url = "http://example.com"
+
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "1"})
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "3"})
+    responses.add(responses.GET, url, status=429, headers={"Retry-After": "7"})
+    responses.add(responses.GET, url, status=200)
+
+    @backoff.on_exception(
+        backoff.runtime,
+        HTTPError,
+        value=lambda e: int(e.response.headers.get("Retry-After")),
+        jitter=None,
+    )
+    def get_url():
+        resp = requests.get(url)
+        resp.raise_for_status()
+        return resp
+
+    resp = get_url()
+    assert resp.status_code == 200
+
+    assert log == [1, 3, 7]