Include test for safety of helper functions

Author: MilesCranmer

test/test_safe_helpers.jl

@@ -0,0 +1,31 @@
+using DynamicExpressions
+using Test
+
+function _square(x)
+    return x^2
+end
+
+operators = OperatorEnum(;
+    binary_operators=[+, -, *, /], unary_operators=[cos, sin, _square]
+)
+@extend_operators operators
+x1, x2, x3 = (i -> Node(Float64; feature=i)).(1:3)
+
+# Should work normally:
+@test _square(x1 + x2 / x3) * x2 + 0.5 isa Node
+
+# But, upon redefining `operators`, we should get errors:
+operators = OperatorEnum(; binary_operators=[+, -, *], unary_operators=[cos, sin, _square])
+
+# Safe:
+@test _square(x1 + x2) * x2 + 0.5 isa Node
+
+# Breaks:
+@test_throws ErrorException _square(x1 + x2 / x3) * x2 + 0.5
+
+operators = OperatorEnum(; binary_operators=[+, -, *, /], unary_operators=[cos, sin])
+# Safe:
+@test (x1 + x2 / x3) * x2 + 0.5 isa Node
+
+# Breaks:
+@test_throws ErrorException _square(x1 + x2 / x3) * x2 + 0.5

test/unittest.jl

@@ -101,3 +101,7 @@ end
 @safetestset "Test containers preserved" begin
     include("test_container_preserved.jl")
 end
+
+@safetestset "Test helpers break upon redefining" begin
+    include("test_safe_helpers.jl")
+end