Merge #1738: test(core): add unit tests for merge trait

fcc0a34 test: add tests for  trait of operations on various data structures, including conflict scenarios and checking for empty structures (pluveto)

Pull request description:

  ### Description

  This update adds unit tests for the `Merge` trait implementations on `BTreeMap`, `BTreeSet`, `Vec`, and tuples. It also includes tests for the `is_empty` and `take` methods to ensure their correct functionality.

  ### Notes to the Reviewers

  - The tests cover basic scenarios for merging collections and checking their emptiness.
  - Consider the potential method name conflict with `BTreeSet`'s existing `take` method.

  ### Changelog Notice

  - Added unit tests for merging functionality and utility methods (`is_empty`, `take`) on various collection types.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits.
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md).
  * [x] I ran `cargo fmt` and `cargo clippy` before committing.

Top commit has no ACKs.

Tree-SHA512: fdcd67ca9127986e9ce9aa9ccc3276aaff127fa9333696c61ff2ca1b37a2ce8f9fe7af8e06ab57dda493741e91fa63a3aba58a1338a17090626225899e6c7588

crates/core/tests/test_merge.rs

@@ -0,0 +1,119 @@
+use std::collections::{BTreeMap, BTreeSet};
+
+use bdk_core::Merge;
+
+#[test]
+fn test_btree_map_merge() {
+    let mut map1: BTreeMap<i32, &str> = BTreeMap::new();
+    map1.insert(1, "a");
+    let mut map2: BTreeMap<i32, &str> = BTreeMap::new();
+    map2.insert(2, "b");
+
+    map1.merge(map2);
+
+    let expected: BTreeMap<i32, &str> = BTreeMap::from([(1, "a"), (2, "b")]);
+    assert_eq!(map1, expected);
+}
+
+#[test]
+fn test_btree_set_merge() {
+    let mut set1: BTreeSet<i32> = BTreeSet::new();
+    set1.insert(1);
+    let mut set2: BTreeSet<i32> = BTreeSet::new();
+    set2.insert(2);
+
+    set1.merge(set2);
+
+    let expected: BTreeSet<i32> = BTreeSet::from([1, 2]);
+    assert_eq!(set1, expected);
+}
+
+#[test]
+fn test_vec_merge() {
+    let mut vec1 = vec![1, 2, 3];
+    let vec2 = vec![4, 5, 6];
+
+    vec1.merge(vec2);
+
+    assert_eq!(vec1, vec![1, 2, 3, 4, 5, 6]);
+}
+
+#[test]
+fn test_tuple_merge() {
+    let mut tuple1 = (vec![1, 2], BTreeSet::from([3]));
+    let tuple2 = (vec![3, 4], BTreeSet::from([4]));
+
+    tuple1.merge(tuple2);
+
+    let expected_vec = vec![1, 2, 3, 4];
+    assert_eq!(tuple1.0, expected_vec);
+    let expected_set: BTreeSet<i32> = BTreeSet::from([3, 4]);
+    assert_eq!(tuple1.1, expected_set);
+}
+
+#[test]
+fn test_is_empty() {
+    let map: BTreeMap<i32, i32> = BTreeMap::new();
+    assert!(Merge::is_empty(&map));
+
+    let set: BTreeSet<i32> = BTreeSet::new();
+    assert!(Merge::is_empty(&set));
+
+    let vec: Vec<i32> = Vec::new();
+    assert!(Merge::is_empty(&vec));
+}
+#[test]
+fn test_take() {
+    let mut map: BTreeMap<i32, i32> = BTreeMap::new();
+    map.insert(1, 1);
+    let taken_map = Merge::take(&mut map);
+    assert_eq!(taken_map, Some(BTreeMap::from([(1, 1)])));
+    assert!(map.is_empty());
+
+    let mut set: BTreeSet<i32> = BTreeSet::new();
+    set.insert(1);
+    let taken_set = Merge::take(&mut set);
+    assert_eq!(taken_set, Some(BTreeSet::from([1])));
+    assert!(set.is_empty());
+
+    let mut vec: Vec<i32> = vec![1];
+    let taken_vec = Merge::take(&mut vec);
+    assert_eq!(taken_vec, Some(vec![1]));
+    assert!(vec.is_empty());
+}
+
+#[test]
+fn test_btree_map_merge_conflict() {
+    let mut map1: BTreeMap<i32, &str> = BTreeMap::new();
+    map1.insert(1, "a");
+    let mut map2: BTreeMap<i32, &str> = BTreeMap::new();
+    map2.insert(1, "b");
+
+    map1.merge(map2);
+
+    let expected: BTreeMap<i32, &str> = BTreeMap::from([(1, "b")]);
+    assert_eq!(map1, expected);
+}
+
+#[test]
+fn test_btree_set_merge_conflict() {
+    let mut set1: BTreeSet<i32> = BTreeSet::new();
+    set1.insert(1);
+    let mut set2: BTreeSet<i32> = BTreeSet::new();
+    set2.insert(1);
+
+    set1.merge(set2);
+
+    let expected: BTreeSet<i32> = BTreeSet::from([1]);
+    assert_eq!(set1, expected);
+}
+
+#[test]
+fn test_vec_merge_duplicates() {
+    let mut vec1 = vec![1, 2, 3];
+    let vec2 = vec![3, 4, 5];
+
+    vec1.merge(vec2);
+
+    assert_eq!(vec1, vec![1, 2, 3, 3, 4, 5]);
+}