diff --git a/src/tests.py b/src/tests.py
new file mode 100644
index 0000000000000000000000000000000000000000..b80e20ae7a9021e9bce2fd81e6b178888707b807
--- /dev/null
+++ b/src/tests.py
@@ -0,0 +1,11 @@
+import primitives
+
+
+
+
+def is_zero(expr):
+    # FIXME
+    return isinstance(expr, primitives.Constant) and expr.Value == 0
+
+def is_one(expr):
+    return isinstance(expr, primitives.Constant) and expr.Value == 1 or is_zero(expr-1)