chore: add logging under tracing feature

tests/tracing/without_tracing.rs

@@ -0,0 +1,61 @@
+//! Tests that the library works correctly without tracing feature
+
+use dagx::{task, DagRunner, Task};
+
+struct Value(i32);
+
+#[task]
+impl Value {
+    async fn run(&self) -> i32 {
+        self.0
+    }
+}
+
+struct Add;
+
+#[task]
+impl Add {
+    async fn run(a: &i32, b: &i32) -> i32 {
+        a + b
+    }
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn test_basic_dag_without_tracing() {
+    let dag = DagRunner::new();
+
+    let a = dag.add_task(Value(2));
+    let b = dag.add_task(Value(3));
+    let sum = dag.add_task(Add).depends_on((&a, &b));
+
+    dag.run(|fut| {
+        tokio::spawn(fut);
+    })
+    .await
+    .unwrap();
+
+    assert_eq!(dag.get(sum).unwrap(), 5);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn test_complex_dag_without_tracing() {
+    let dag = DagRunner::new();
+
+    // Create multiple layers
+    let v1 = dag.add_task(Value(1));
+    let v2 = dag.add_task(Value(2));
+    let v3 = dag.add_task(Value(3));
+    let v4 = dag.add_task(Value(4));
+
+    let sum12 = dag.add_task(Add).depends_on((&v1, &v2));
+    let sum34 = dag.add_task(Add).depends_on((&v3, &v4));
+    let final_sum = dag.add_task(Add).depends_on((&sum12, &sum34));
+
+    dag.run(|fut| {
+        tokio::spawn(fut);
+    })
+    .await
+    .unwrap();
+
+    assert_eq!(dag.get(final_sum).unwrap(), 10);
+}