init: zero-dep dns-over-https resolver

tests/test_resolver.py

@@ -0,0 +1,73 @@
+import struct
+
+import pydoh.resolver as resolver_module
+from pydoh.resolver import ResolveError, resolve
+
+
+def _make_response(query_id, ip):
+    header = struct.pack(">HHHHHH", query_id, 0x8180, 1, 1, 0, 0)
+    name = b"\x07example\x03com\x00"
+    question = name + struct.pack(">HH", 1, 1)
+    rdata = bytes(int(part) for part in ip.split("."))
+    answer = b"\xc0\x0c" + struct.pack(">HHIH", 1, 1, 300, 4) + rdata
+    return header + question + answer
+
+
+def test_resolve_returns_ip(monkeypatch):
+    def fake_doh_request(provider, query, timeout):
+        query_id = struct.unpack(">H", query[:2])[0]
+        return _make_response(query_id, "93.184.216.34")
+
+    monkeypatch.setattr(resolver_module, "_doh_request", fake_doh_request)
+    resolver_module._cache.clear()
+
+    ips = resolve("example.com", use_cache=False)
+    assert ips == ["93.184.216.34"]
+
+
+def test_resolve_uses_cache(monkeypatch):
+    calls = []
+
+    def fake_doh_request(provider, query, timeout):
+        calls.append(1)
+        query_id = struct.unpack(">H", query[:2])[0]
+        return _make_response(query_id, "1.1.1.1")
+
+    monkeypatch.setattr(resolver_module, "_doh_request", fake_doh_request)
+    resolver_module._cache.clear()
+
+    resolve("example.com", use_cache=True)
+    resolve("example.com", use_cache=True)
+    assert len(calls) == 1
+
+
+def test_resolve_falls_back_to_next_provider(monkeypatch):
+    attempts = []
+
+    def fake_doh_request(provider, query, timeout):
+        attempts.append(provider.name)
+        if provider.name == "cloudflare":
+            raise RuntimeError("simulated failure")
+        query_id = struct.unpack(">H", query[:2])[0]
+        return _make_response(query_id, "8.8.8.8")
+
+    monkeypatch.setattr(resolver_module, "_doh_request", fake_doh_request)
+    resolver_module._cache.clear()
+
+    ips = resolve("example.com", use_cache=False)
+    assert ips == ["8.8.8.8"]
+    assert attempts[0] == "cloudflare"
+
+
+def test_resolve_raises_when_all_providers_fail(monkeypatch):
+    def fake_doh_request(provider, query, timeout):
+        raise RuntimeError("down")
+
+    monkeypatch.setattr(resolver_module, "_doh_request", fake_doh_request)
+    resolver_module._cache.clear()
+
+    try:
+        resolve("example.com", use_cache=False)
+        assert False, "expected ResolveError"
+    except ResolveError:
+        pass