diff --git a/test/mitmproxy/net/http/http1/test_read_sansio.py b/test/mitmproxy/net/http/http1/test_read_sansio.py
new file mode 100644
index 000000000..a204fed06
--- /dev/null
+++ b/test/mitmproxy/net/http/http1/test_read_sansio.py
@@ -0,0 +1,192 @@
+import pytest
+
+from mitmproxy import exceptions
+from mitmproxy.net.http import Headers
+from mitmproxy.net.http.http1.read_sansio import (
+    read_request_head,
+    read_response_head, expected_http_body_size,
+    _read_request_line, _read_response_line,
+    _read_headers,
+)
+from mitmproxy.test.tutils import treq, tresp
+
+
+def test_read_request_head():
+    rfile = [
+        b"GET / HTTP/1.1\r\n",
+        b"Content-Length: 4\r\n",
+    ]
+    r = read_request_head(rfile)
+    assert r.method == "GET"
+    assert r.headers["Content-Length"] == "4"
+    assert r.content is None
+
+
+def test_read_response_head():
+    rfile = [
+        b"HTTP/1.1 418 I'm a teapot\r\n",
+        b"Content-Length: 4\r\n",
+    ]
+    r = read_response_head(rfile)
+    assert r.status_code == 418
+    assert r.headers["Content-Length"] == "4"
+    assert r.content is None
+
+
+def test_expected_http_body_size():
+    # Expect: 100-continue
+    assert expected_http_body_size(
+        treq(headers=Headers(expect="100-continue", content_length="42")),
+        expect_continue_as_0=True
+    ) == 0
+    # Expect: 100-continue
+    assert expected_http_body_size(
+        treq(headers=Headers(expect="100-continue", content_length="42")),
+        expect_continue_as_0=False
+    ) == 42
+
+    # http://tools.ietf.org/html/rfc7230#section-3.3
+    assert expected_http_body_size(
+        treq(method=b"HEAD"),
+        tresp(headers=Headers(content_length="42"))
+    ) == 0
+    assert expected_http_body_size(
+        treq(method=b"CONNECT"),
+        tresp()
+    ) == 0
+    for code in (100, 204, 304):
+        assert expected_http_body_size(
+            treq(),
+            tresp(status_code=code)
+        ) == 0
+
+    # chunked
+    assert expected_http_body_size(
+        treq(headers=Headers(transfer_encoding="chunked")),
+    ) is None
+
+    # explicit length
+    for val in (b"foo", b"-7"):
+        with pytest.raises(exceptions.HttpSyntaxException):
+            expected_http_body_size(
+                treq(headers=Headers(content_length=val))
+            )
+    assert expected_http_body_size(
+        treq(headers=Headers(content_length="42"))
+    ) == 42
+
+    # more than 1 content-length headers with same value
+    assert expected_http_body_size(
+        treq(headers=Headers([(b'content-length', b'42'), (b'content-length', b'42')]))
+    ) == 42
+
+    # more than 1 content-length headers with conflicting value
+    with pytest.raises(exceptions.HttpSyntaxException):
+        expected_http_body_size(
+            treq(headers=Headers([(b'content-length', b'42'), (b'content-length', b'45')]))
+        )
+
+    # no length
+    assert expected_http_body_size(
+        treq(headers=Headers())
+    ) == 0
+    assert expected_http_body_size(
+        treq(headers=Headers()), tresp(headers=Headers())
+    ) == -1
+
+
+def test_read_request_line():
+    def t(b):
+        return _read_request_line(b)
+
+    assert (t(b"GET / HTTP/1.1") ==
+            ("", 0, b"GET", b"", b"", b"/", b"HTTP/1.1"))
+    assert (t(b"OPTIONS * HTTP/1.1") ==
+            ("", 0, b"OPTIONS", b"", b"", b"*", b"HTTP/1.1"))
+    assert (t(b"CONNECT foo:42 HTTP/1.1") ==
+            ("foo", 42, b"CONNECT", b"", b"foo:42", b"", b"HTTP/1.1"))
+    assert (t(b"GET http://foo:42/bar HTTP/1.1") ==
+            ("foo", 42, b"GET", b"http", b"foo:42", b"/bar", b"HTTP/1.1"))
+
+    with pytest.raises(ValueError):
+        t(b"GET / WTF/1.1")
+    with pytest.raises(ValueError):
+        t(b"CONNECT example.com HTTP/1.1")  # port missing
+    with pytest.raises(ValueError):
+        t(b"GET ws://example.com/ HTTP/1.1")  # port missing
+    with pytest.raises(ValueError):
+        t(b"this is not http")
+    with pytest.raises(ValueError):
+        t(b"")
+
+
+def test_read_response_line():
+    def t(b):
+        return _read_response_line(b)
+
+    assert t(b"HTTP/1.1 200 OK") == (b"HTTP/1.1", 200, b"OK")
+    assert t(b"HTTP/1.1 200") == (b"HTTP/1.1", 200, b"")
+
+    # https://github.com/mitmproxy/mitmproxy/issues/784
+    assert t(b"HTTP/1.1 200 Non-Autoris\xc3\xa9") == (b"HTTP/1.1", 200, b"Non-Autoris\xc3\xa9")
+
+    with pytest.raises(ValueError):
+        assert t(b"HTTP/1.1")
+
+    with pytest.raises(ValueError):
+        t(b"HTTP/1.1 OK OK")
+    with pytest.raises(ValueError):
+        t(b"WTF/1.1 200 OK")
+    with pytest.raises(ValueError):
+        t(b"")
+
+
+class TestReadHeaders:
+    @staticmethod
+    def _read(data):
+        return _read_headers(data.splitlines(keepends=True))
+
+    def test_read_simple(self):
+        data = (
+            b"Header: one\r\n"
+            b"Header2: two\r\n"
+        )
+        headers = self._read(data)
+        assert headers.fields == ((b"Header", b"one"), (b"Header2", b"two"))
+
+    def test_read_multi(self):
+        data = (
+            b"Header: one\r\n"
+            b"Header: two\r\n"
+        )
+        headers = self._read(data)
+        assert headers.fields == ((b"Header", b"one"), (b"Header", b"two"))
+
+    def test_read_continued(self):
+        data = (
+            b"Header: one\r\n"
+            b"\ttwo\r\n"
+            b"Header2: three\r\n"
+        )
+        headers = self._read(data)
+        assert headers.fields == ((b"Header", b"one\r\n two"), (b"Header2", b"three"))
+
+    def test_read_continued_err(self):
+        data = b"\tfoo: bar\r\n"
+        with pytest.raises(ValueError):
+            self._read(data)
+
+    def test_read_err(self):
+        data = b"foo"
+        with pytest.raises(ValueError):
+            self._read(data)
+
+    def test_read_empty_name(self):
+        data = b":foo"
+        with pytest.raises(ValueError):
+            self._read(data)
+
+    def test_read_empty_value(self):
+        data = b"bar:"
+        headers = self._read(data)
+        assert headers.fields == ((b"bar", b""),)