add I2CScan operation

circuitpython_mocks/_mixins.py

@@ -6,6 +6,7 @@
         I2CRead,
         I2CWrite,
         I2CTransfer,
+        I2CScan,
         SPIRead,
         SPIWrite,
         SPITransfer,
@@ -72,6 +73,7 @@ def __init__(self, **kwargs) -> None:
                 I2CRead,
                 I2CWrite,
                 I2CTransfer,
+                I2CScan,
                 SPIRead,
                 SPIWrite,
                 SPITransfer,

circuitpython_mocks/busio/__init__.py

@@ -30,6 +30,7 @@
     I2CRead,
     I2CWrite,
     I2CTransfer,
+    I2CScan,
     SPIRead,
     SPIWrite,
     SPITransfer,
@@ -82,9 +83,17 @@ def __init__(
         super().__init__()
 
     def scan(self) -> List[int]:
-        """Returns an empty list.
-        Use :py:meth:`pytest.MonkeyPatch.setattr()` to change this output."""
-        return []
+        """Returns a list of I2C device addresses.
+
+        .. mock-expects::
+
+            This function will check against `I2CScan`
+            :py:attr:`~circuitpython_mocks._mixins.Expecting.expectations`.
+        """
+        assert self.expectations, "no expectation found for I2C.scan()"
+        op = self.expectations.popleft()
+        assert isinstance(op, I2CScan), f"I2CScan operation expected, found {repr(op)}"
+        return op.expected
 
     def readfrom_into(
         self,

circuitpython_mocks/busio/operations.py

@@ -1,3 +1,4 @@
+from typing import List
 import sys
 import circuitpython_typing as cir_py_types
 
@@ -140,6 +141,23 @@ def __repr__(self) -> str:
         )
 
 
+class I2CScan:
+    """A class to identify a scan operation over a
+    :py:class:`~circuitpython_mocks.busio.I2C` bus.
+
+    The given ``expected`` value will be the result of `I2C.scan()`.
+    """
+
+    def __init__(self, expected: List[int]) -> None:
+        for val in expected:
+            assert val <= 0x7F, f"scan result {val} is not a valid I2C address"
+        self.expected = expected
+
+    def __repr__(self) -> str:
+        stringify = ", ".join(["%02X" % x for x in self.expected])
+        return f"<I2CScan expected='[{stringify}]'>"
+
+
 class SPIRead(_Read):
     """A class to identify a read operation over a
     :py:class:`~circuitpython_mocks.busio.SPI` bus."""

docs/busio.rst

@@ -30,6 +30,7 @@
     .. autoclass:: circuitpython_mocks.busio.operations.I2CRead
     .. autoclass:: circuitpython_mocks.busio.operations.I2CWrite
     .. autoclass:: circuitpython_mocks.busio.operations.I2CTransfer
+    .. autoclass:: circuitpython_mocks.busio.operations.I2CScan
 
     SPI operations
     **************

tests/test_i2c.py

@@ -1,7 +1,7 @@
 import pytest
 from collections import deque
 from circuitpython_mocks import busio, board
-from circuitpython_mocks.busio.operations import I2CTransfer
+from circuitpython_mocks.busio.operations import I2CTransfer, I2CScan
 
 
 @pytest.mark.parametrize(
@@ -19,8 +19,18 @@ def test_singleton(board_i2c: busio.I2C, busio_i2c: busio.I2C):
     assert isinstance(board_i2c.expectations, deque)
     assert board_i2c == busio_i2c
 
-    board_i2c.expectations.append(I2CTransfer(address, bytearray(1), bytearray(1)))
+    board_i2c.expectations.extend(
+        [
+            I2CScan([address]),
+            I2CTransfer(address, bytearray(1), bytearray(1)),
+        ]
+    )
     assert busio_i2c.expectations == board_i2c.expectations
+
+    assert busio_i2c.try_lock()
+    assert address in board_i2c.scan()
+    busio_i2c.unlock()
+
     buffer = bytearray(1)
     assert board_i2c.try_lock()
     assert not busio_i2c.try_lock()

tests/test_i2c_fixture.py

@@ -15,8 +15,6 @@ def test_i2c(mock_blinka_imports):
     address = 0x42
     # do setup
     with I2C(board.SCL, board.SDA) as i2c_bus:
-        assert i2c_bus.scan() == []
-
         # set expectation for probing performed by I2CDevice.__init__()
         i2c_bus.expectations.append(I2CWrite(address, b""))
         # set expectations for I2C bus