tests/unix/mod_os: Add test for os module.

This adds a test to get coverage of the unix port-specific implementation
of the `os` module.

Signed-off-by: David Lechner <david@pybricks.com>

tests/unix/mod_os.py

@@ -0,0 +1,21 @@
+# This module is not entirely compatible with CPython
+import os
+
+
+os.putenv("TEST_VARIABLE", "TEST_VALUE")
+
+print(os.getenv("TEST_VARIABLE"))
+print(os.getenv("TEST_VARIABLE", "TEST_DEFAULT_VALUE"))
+
+os.unsetenv("TEST_VARIABLE")
+
+print(os.getenv("TEST_VARIABLE"))
+print(os.getenv("TEST_VARIABLE", "TEST_DEFAULT_VALUE"))
+
+print(os.system("true"))
+
+rand = os.urandom(4)
+print(type(rand) is bytes, len(rand))
+
+os.errno(2)
+print(os.errno())

tests/unix/mod_os.py.exp

@@ -0,0 +1,7 @@
+TEST_VALUE
+TEST_VALUE
+None
+TEST_DEFAULT_VALUE
+0
+True 4
+2