Add tests(and test false positives cause I was nervous lol)

src/core/graph/tests_cpu.rs

@@ -68,6 +68,36 @@ mod tests {
     create_test!(test_add_1_2, add, F32, 1f32, 2f32, 3f32);
     create_test!(test_sub_1_2, sub, F32, 1f32, 2f32, -1f32);
 
+    #[test]
+    fn test_cte_happened() {
+        let mut ctx = Context::new();
+        let a = ctx.parameter("a", [], xla::ElementType::F32).expect("a");
+        let b = ctx.parameter("b", [], xla::ElementType::F32).expect("b");
+
+        let a_p_b = ctx.add(a, b).expect("a + b");
+        let a_p_b_again = ctx.add(a, b).expect("a + b again");
+
+        let res = ctx.mul(a_p_b, a_p_b_again).expect("(a + b) * (a + b)");
+        let subterm_extract = ctx.extract_subterms(&[res], 10).expect("CTE");
+
+        assert!(subterm_extract);
+    }
+
+    #[test]
+    fn test_cte_no_false_positives() {
+        let mut ctx = Context::new();
+        let a = ctx.parameter("a", [], xla::ElementType::F32).expect("a");
+        let b = ctx.parameter("b", [], xla::ElementType::F32).expect("b");
+
+        let a_p_b = ctx.add(a, b).expect("a + b");
+
+        let c = ctx.parameter("c", [], xla::ElementType::F32).expect("c");
+        let res = ctx.mul(a_p_b, c).expect("(a+b) * c");
+        let subterm_extract = ctx.extract_subterms(&[res], 10).expect("CTE");
+
+        assert!(!subterm_extract);
+    }
+
     #[test]
     fn test_hash_node() {
         let mut ctx = Context::new();