diff --git a/stream2py/tests/test_design.py b/stream2py/tests/test_design.py
new file mode 100644
index 0000000..1f7080d
--- /dev/null
+++ b/stream2py/tests/test_design.py
@@ -0,0 +1,166 @@
+"""Interface definition based on Stream2py design notes
+https://github.com/i2mint/stream2py/wiki/Stream2py-design-notes
+
+TODO: Separate protocols and reorganize tests as pytests
+"""
+from typing import Iterator, Callable, Protocol
+
+CursorFunc = Callable
+# example of a CursorFunc: iter([1,2,3]).__next__
+
+
+class Reader(Protocol):
+    def __getitem__(self, item):
+        """Sliceable and single point"""
+
+    def __iter__(self):
+        """Iterable"""
+
+    def __next__(self):
+        """Iterator"""
+
+    def __call__(self, *args, **kwargs):
+        """CursorFunc"""
+        return self.__next__()
+
+    def __enter__(self):
+        """Starts source and populate buffer"""
+        self.enter()
+        return self
+
+    def __exit__(self, exc_type=None, exc_val=None, exc_tb=None):
+        """Stop source and buffer when all readers are stopped"""
+        return self.exit(exc_type, exc_val, exc_tb)
+
+    def __del__(self):
+        """Ensure proper closing and clean up when instance will be garbage collected
+
+        :return:
+        """
+        self.__exit__()
+
+    def exit(self, exc_type=None, exc_val=None, exc_tb=None):
+        pass
+
+    def enter(self):
+        pass
+
+
+class Buffer(Protocol):
+    pass
+
+
+class Source(Protocol):
+    def open_reader(self, **reader_kw) -> Reader:
+        """Make reader for source buffer data.
+        Can be used as a context manager similar to builtin open()
+
+        :param reader_kw:
+        :return:
+        """
+
+    def config_buffer(self, **buffer_kw):
+        pass
+
+    @property
+    def opened(self) -> bool:
+        """Source is opened and running either by enter(), context manager, or open_reader()
+
+        :return: 
+        """
+        return False
+
+    def exit(self, exc_type=None, exc_val=None, exc_tb=None):
+        pass
+
+    def enter(self):
+        pass
+
+    def __enter__(self):
+        self.enter()
+        return self
+
+    def __exit__(self, exc_type=None, exc_val=None, exc_tb=None):
+        return self.exit(exc_type, exc_val, exc_tb)
+
+    def __del__(self):
+        """Ensure proper closing and clean up when instance will be garbage collected
+
+        :return:
+        """
+        self.__exit__()
+
+
+# Multireader context management
+#   example: SlabsIter
+
+
+# Source Basic Interface
+########################
+s = {}  # kwargs for initializing source
+
+# Opening and Closing Source
+# ==========================
+
+# source as context manager
+src_cm = Source(**s)
+assert not src_cm.opened
+with src_cm:
+    assert src_cm.opened
+    reader_of_src_cm = src_cm.open_reader()
+assert not src_cm.opened
+del src_cm
+
+# open_reader as context manager
+src_or_as_cm = Source(**s)
+assert not src_or_as_cm.opened
+with src_or_as_cm.open_reader() as reader_of_src_or_as_cm:
+    assert src_or_as_cm.opened
+assert not src_or_as_cm.opened
+del src_or_as_cm
+
+# open_reader
+src_or = Source(**s)
+assert not src_or.opened
+reader_of_src_or1 = src_or.open_reader()
+reader_of_src_or2 = src_or.open_reader()
+assert src_or.opened
+reader_of_src_or1.exit()
+assert src_or.opened  # remain open while reader has not closed
+reader_of_src_or2.exit()
+assert not src_or.opened  # close if all readers have exited
+del src_or
+
+src_or = Source(**s)
+assert not src_or.opened
+reader_of_src_or1 = src_or.open_reader()
+reader_of_src_or2 = src_or.open_reader()
+assert src_or.opened
+src_or.exit()  # exit source to close source and all readers
+assert not src_or.opened
+del src_or
+
+
+# Reader Interface
+##################
+
+
+def mk_data_gen_for_source():
+    for i in range(10):
+        start = i * 10
+        end = start + 10
+        yield dict(bt=start, tt=end, data=list(range(start, end)))
+
+
+src = Source(**s)
+reader = src.open_reader()
+
+# query data items by bt only inclusive
+assert reader[1:11] == [dict(bt=10, tt=20, data=list(range(10, 20)))]
+
+# query merges joinable continuous data
+assert reader[1:21] == dict(bt=1, tt=21, data=list(range(1, 21)))
+
+# query data items by bt/tt inclusive
+assert reader[1:11] == []
+assert reader[1:21] == [dict(bt=10, tt=20, data=list(range(10, 20)))]