test: add tests to drop_unused_requests option

tests/integration/test_config.py

@@ -5,6 +5,7 @@ from urllib.request import urlopen
 import pytest
 
 import vcr
+from vcr.cassette import Cassette
 
 
 def test_set_serializer_default_config(tmpdir, httpbin):
@@ -80,3 +81,20 @@ def test_dont_record_on_exception(tmpdir):
             assert b"Not in content" in urlopen("http://httpbin.org/get").read()
 
     assert not os.path.exists(str(tmpdir.join("dontsave2.yml")))
+
+def test_set_drop_unused_requests(tmpdir, httpbin):
+    my_vcr = vcr.VCR(drop_unused_requests=True)
+    file = str(tmpdir.join("test.yaml"))
+
+    with my_vcr.use_cassette(file):
+        urlopen(httpbin.url)
+        urlopen(httpbin.url + "/get")
+
+    cassette = Cassette.load(path=file)
+    assert len(cassette) == 2
+
+    with my_vcr.use_cassette(file):
+        urlopen(httpbin.url)
+
+    cassette = Cassette.load(path=file)
+    assert len(cassette) == 1

tests/unit/test_cassettes.py

@@ -11,6 +11,7 @@ import yaml
 from vcr.cassette import Cassette
 from vcr.errors import UnhandledHTTPRequestError
 from vcr.patch import force_reset
+from vcr.request import Request
 from vcr.stubs import VCRHTTPSConnection
 
 
@@ -394,3 +395,25 @@ def test_find_requests_with_most_matches_many_similar_requests(mock_get_matchers
         (1, ["method", "path"], [("query", "failed : query")]),
         (3, ["method", "path"], [("query", "failed : query")]),
     ]
+
+
+def test_used_interactions(tmpdir):
+    interactions = [
+        {"request": {"body": "", "uri": "foo1", "method": "GET", "headers": {}}, "response": "bar1"},
+        {"request": {"body": "", "uri": "foo2", "method": "GET", "headers": {}}, "response": "bar2"},
+        {"request": {"body": "", "uri": "foo3", "method": "GET", "headers": {}}, "response": "bar3"}
+    ]
+    file = tmpdir.join("test_cassette.yml")
+    file.write(yaml.dump({"interactions": [interactions[0], interactions[1]]}))
+
+    cassette = Cassette.load(path=str(file))
+    request = Request._from_dict(interactions[1]["request"])
+    cassette.play_response(request)
+    assert len(cassette._played_interactions) < len(cassette._old_interactions)
+
+    request = Request._from_dict(interactions[2]["request"])
+    cassette.append(request, interactions[2]["response"])
+    assert len(cassette._new_interactions()) == 1
+
+    used_interactions = cassette._played_interactions + cassette._new_interactions()
+    assert len(used_interactions) == 2