Add some tests

.gitignore

@@ -2,3 +2,4 @@ build/
 dist/
 wheelhouse/
 *.egg-info
+__pycache__/

test_zlib_into.py

+import zlib
+
+import pytest
+
+from zlib_into import compress_into, decompress_into
+
+def test_compress_into():
+    buf_size = 5000
+    data_in = b'abcde' * 5000
+    buf = bytearray(buf_size)
+    n_bytes_out = compress_into(data_in, buf)
+
+    assert isinstance(n_bytes_out, int)
+    assert 0 < n_bytes_out < buf_size
+
+    # Remaining space in buffer should not have been touched
+    assert bytes(buf[n_bytes_out:]) == b'\0' * (buf_size - n_bytes_out)
+
+    # Roundtrip
+    assert zlib.decompress(buf[:n_bytes_out]) == data_in
+
+
+def test_compress_into_err():
+    buf_size = 5000
+    data_in = b'abcde' * 5000
+    buf = bytearray(5000)
+    with pytest.raises(BufferError):
+        compress_into(memoryview(data_in)[::2], buf)  # Input not contiguous
+
+    with pytest.raises(TypeError):
+        compress_into(data_in, memoryview(buf).toreadonly())  # Output not writable
+
+    with pytest.raises(BufferError):
+        compress_into(data_in, buf[:10])  # Output too small
+
+
+def test_decompress_into():
+    expanded_data = b'abcde' * 5000
+    compressed_data = zlib.compress(expanded_data)
+    buf = bytearray(len(expanded_data) + 10)
+
+    n_bytes_out = decompress_into(compressed_data, buf)
+
+    assert isinstance(n_bytes_out, int)
+    assert n_bytes_out == len(expanded_data)
+    assert buf[:n_bytes_out] == expanded_data
+
+    # Remaining space in buffer should not have been touched
+    assert bytes(buf[n_bytes_out:]) == b'\0' * (len(buf) - n_bytes_out)
+
+    # Exactly the right amount of space
+    buf2 = bytearray(len(expanded_data))
+    assert decompress_into(compressed_data, buf2) == len(expanded_data)
+
+    # Not enough space, by 1 byte
+    buf3 = bytearray(len(expanded_data) - 1)
+    with pytest.raises(BufferError):
+        decompress_into(compressed_data, buf3)
+
+
+def test_decompress_into_err():
+    expanded_data = b'abcde' * 5000
+    compressed_data = zlib.compress(expanded_data)
+    buf = bytearray(len(expanded_data) + 10)
+
+    with pytest.raises(BufferError):
+        compress_into(memoryview(compressed_data)[::2], buf)  # Input not contiguous
+
+    with pytest.raises(TypeError):
+        compress_into(compressed_data, memoryview(buf).toreadonly())  # Output not writable