Added test for stack overflow post

Author: Sylvain MARIE

mini_lambda/tests/test_so.py

@@ -0,0 +1,42 @@
+from __future__ import print_function
+
+
+def test_so1(capsys):
+    """Test for the solution at https://stackoverflow.com/a/55760092/7262247"""
+    with capsys.disabled():
+
+        # your source code util
+
+        from mini_lambda import x, is_mini_lambda_expr
+        import inspect
+
+        def get_source_code_str(f):
+            if is_mini_lambda_expr(f):
+                return f.to_string()
+            else:
+                return inspect.getsource(f)
+
+        # test it
+
+        def foo(arg1, arg2):
+            # do something with args
+            a = arg1 + arg2
+            return a
+
+    print()
+    print(get_source_code_str(foo))
+    print(get_source_code_str(x ** 2))
+
+    captured = capsys.readouterr()
+
+    with capsys.disabled():
+        print(captured.out)
+
+        assert captured.out == """
+        def foo(arg1, arg2):
+            # do something with args
+            a = arg1 + arg2
+            return a
+
+x ** 2
+"""